Mark Sundberg – 1950 Present

Biography

The trajectory of contemporary behavior analysis, particularly in its clinical application to communicative disorders and pediatric neurodevelopmental conditions, has been profoundly shaped by the scholarly and programmatic contributions of Mark L. Sundberg. Born in 1950, Sundberg emerged during an era when the broader discipline of psychology was undergoing profound epistemological transitions. While mid-century academic discourse witnessed the rapid ascendancy of cognitive psycholinguistics, Sundberg aligned his career with the foundational, radical behavioral framework established by B. F. Skinner. Rather than regarding human language as the externalized readout of an innate, internal mental processor, Sundberg dedicated his scholarship to an uncompromisingly functional approach: treating verbal behavior as learned operant behavior governed by environmental antecedents, motivating operations, and consequence histories.

Sundberg’s legacy is defined by a rare synthesis of rigorous conceptual behavior analysis, experimental laboratory validation, and transformative curriculum development. Over more than four decades of dedicated service as a researcher, editor, clinician, and educator, he transformed Skinner’s 1957 treatise, Verbal Behavior, from an ostensibly abstract theoretical classification system into an empirical, clinically actionable science. His efforts catalyzed the development of widely implemented, criterion-referenced behavioral assessments, most notably the Verbal Behavior Milestones Assessment and Placement Program (VB-MAPP), as well as foundational clinical protocols that continue to dictate evidence-based intervention paradigms for individuals with autism spectrum disorder (ASD) and other intellectual or developmental disabilities worldwide.

To fully appreciate Sundberg’s enduring impact, one must systematically examine the intersection of his intellectual lineage under the mentorship of Jack Michael at Western Michigan University, his institutional initiatives in establishing peer-reviewed outlets such as The Analysis of Verbal Behavior, his groundbreaking collaborative curricular texts, and his technical elucidations of complex verbal processes including joint control, intraverbal relations, and autoclitic frames. This treatise provides an exhaustive, multi-dimensional academic evaluation of Mark Sundberg’s life, theoretical evolution, methodological innovations, and sustained influence on applied behavior analysis and the functional analysis of verbal behavior from 1950 to the present day.

1. Introduction and Biographical Foundations of Mark Sundberg (1950–Present)

1.1 Early Life, Intellectual Formations, and Historical Milieu

Mark L. Sundberg was born in 1950, entering an intellectual landscape marked by the rapid institutionalization of operant psychology and the formalization of applied behavior analysis. The mid-twentieth century was characterized by a fundamental schism within the behavioral sciences. In one camp, early cognitive psychology and transformational generative grammar—championed by Noam Chomsky—sought to explain human language through hypothetical cognitive architectures, innate linguistic acquisition devices, and computational metaphors of mind. Conversely, the radical behaviorist tradition initiated by B. F. Skinner posited that human communicative acts were empirical, observable behaviors maintained and shaped by external environmental variables. During his formative years, Sundberg encountered these competing philosophical currents, developing an early, profound skepticism toward structuralist paradigms that prioritized linguistic form, syntax, and abstract lexical repositories over measurable behavioral function.

Sundberg’s early academic pursuits coalesced around experimental psychology and human learning systems during the early 1970s. As the initial demonstrations of operant conditioning techniques began expanding outside basic animal research laboratories into community mental health centers and state psychiatric facilities, Sundberg observed the immense practical limitations of prevailing intervention models for non-verbal or language-delayed individuals. Across institutional and clinical settings, individuals diagnosed with profound neurodevelopmental disorders, childhood schizophrenia, or infantile autism were largely subjected to rudimentary stimulus-response conditioning drills, psychiatric containment, or psychodynamic therapies that lacked empirical efficacy. Recognizing the immense human cost of these theoretical inadequacies, Sundberg dedicated his emergent intellectual career to deciphering the environmental conditions under which functional communication could be established, sustained, and systematically expanded in severely language-impaired populations.

This early focus positioned Sundberg at the avant-garde of second-generation behavior analysts who sought to demonstrate that operant psychology was not merely effective for remediating disruptive, topography-based behaviors, but was equally capable of explaining and generating humanity’s most complex symbolic and linguistic repertoires. His foundational orientation toward neurodevelopmental populations during the early to mid-1970s laid the bedrock for a lifetime of clinical innovations, driven by the conviction that the absence of functional speech was not an immutable biological verdict, but an instructional and behavioral challenge that demanded an experimentally validated technology of teaching.

1.2 Doctoral Training Under Jack Michael at Western Michigan University

The decisive catalyst in Sundberg’s scientific trajectory occurred upon his entry into the graduate program in behavior analysis at Western Michigan University (WMU) in Kalamazoo, Michigan. During the 1970s, WMU had established itself as the preeminent global center for radical behaviorism, basic operant research, and conceptual behavioral innovation. Central to this vibrant intellectual environment was Dr. Jack Michael, an iconic behavior analyst whose pedantic rigor, deep conceptual clarity, and unyielding commitment to Skinnerian theory attracted the most promising behavioral scholars of the generation. Sundberg entered into an intense academic apprenticeship under Michael, an association that would fundamentally anchor his scholarship for the remainder of his career.

Under Michael’s direct tutelage, Sundberg underwent intensive immersion in B. F. Skinner’s seminal 1957 work, Verbal Behavior. While the broader field of psychology had largely cast Skinner’s text aside following Chomsky’s hostile 1959 review, Jack Michael maintained that the book was Skinner’s crowning conceptual achievement—a brilliant, highly sophisticated taxonomy awaiting empirical translation and clinical application. Michael instilled in Sundberg an uncompromising standard of conceptual fidelity. Students within this laboratory were taught to scrutinize every verbal episode with extreme precision, parsing the exact antecedent conditions, discriminative stimuli, motivating states, and consequential contingencies operating on both the speaker and the listener. This rigorous training inoculated Sundberg against the mentalistic explanatory fictions pervasive in mainstream developmental psychology.

Sundberg’s doctoral dissertation research at WMU culminated in the completion of his Ph.D. in Applied Behavior Analysis in 1980. His doctoral work was explicitly focused on the empirical validation of verbal operant typologies, examining how distinct functional environmental variables governed different verbal responses. Sundberg conducted meticulous laboratory and applied experiments aimed at proving that communicative topographies—such as requesting versus naming an object—were functionally independent operants rather than homogeneous manifestations of an underlying lexical knowledge base. The rigorous, peer-reviewed execution of his doctoral research demonstrated that the verbal operants described conceptually by Skinner could be isolated, measured, and systematically manipulated, thereby laying the empirical groundwork for what would become an international movement in verbal behavior intervention.

1.3 Chronological Overview of Academic Appointments and Clinical Positions

Following the completion of his doctorate in 1980, Sundberg pursued a diversified professional path that deliberately balanced clinical leadership, institutional consultation, and sustained academic productivity. Recognizing that the conceptual elegance of the verbal operant paradigm had to be validated in clinical environments, Sundberg assumed various directorships and behavioral consultation roles in both public and private treatment facilities. In these early postdoctoral years, he established intensive behavioral intervention programs for children and adults presenting with profound communication deficits, behavioral regressions, and refractory aberrant repertoires. His clinical leadership during this era proved that verbal behavior methodology could yield rapid functional gains where conventional speech-language pathology and traditional early intensive behavioral interventions had stalled.

Over the ensuing decades, Dr. Sundberg served as a primary behavioral consultant to dozens of public school districts, specialized regional centers, and clinical autism programs across the United States and internationally. His clinical practice became an ongoing research laboratory; school classrooms and clinical rooms were transformed into settings where prompt hierarchies, transfer of stimulus control procedures, and motivating operation manipulations were systematically refined. Concurrently, Sundberg maintained an active presence in higher education, holding adjunct faculty appointments and serving as a doctoral and master’s thesis advisor at institutions including Western Michigan University and Florida State University. Through these academic connections, he directly mentored cohorts of behavior analysts, ensuring the transmission of rigorous Skinnerian methodology to subsequent generations of clinical practitioners.

Sundberg’s institutional stewardship within the global behavior analysis community has been equally profound. A board-certified behavior analyst at the doctoral level (BCBA-D), he committed decades of voluntary leadership to the Association for Behavior Analysis International (ABAI). He served as the Publication Board Chair for ABAI, stewarding the scientific integrity of the organization’s foundational journals. Additionally, Sundberg was twice elected president of the Northern California Association for Behavior Analysis (NorCal ABA), and was appointed to the Board of Directors of the B. F. Skinner Foundation. Through these formal institutional roles, Sundberg successfully advocated for the broader integration of verbal behavior coursework into standardized international accreditation curricula for behavior analysts, fundamentally altering the training benchmarks of the profession.

2. Theoretical Foundations: Revitalizing Skinner’s Verbal Behavior

2.1 The Epistemological Shift from Structural Linguistics to Functional Analysis

The conceptual cornerstone of Mark Sundberg’s entire body of work rests upon an uncompromising epistemological divergence from structural linguistics. Traditional linguistic and psycholinguistic frameworks, exemplified by structuralist and Chomskyan paradigms, treat language primarily as a formal, symbolic, and internalized structural system. In these mainstream traditions, language is deconstructed into phonemes, morphemes, syntax, semantics, and pragmatics. Words are conceptualized as symbolic tokens stored within a hypothetical mental lexicon; communicative acts are seen as the encoding and decoding of internal cognitive representations. Sundberg asserted, echoing Skinner (1957), that this formalist paradigm provides a purely descriptive account of language structure while systematically failing to identify the functional, environmental variables responsible for the initial emission, ongoing maintenance, and situational probability of communicative behavior.

In contrast to structural models, Sundberg championed the three-term contingency—the fundamental unit of operant behavior consisting of an antecedent discriminative stimulus ($S^D$), a behavioral response ($R$), and a reinforcing consequence ($S^R$)—as the only scientifically sufficient framework for explicating human communication. Within Sundberg’s functional framework, the traditional, monolithic concept of “words” and “meanings” is deconstructed. A vocalization, manual sign, or graphical selection is not inherently endowed with meaning; rather, its meaning resides entirely within the environmental variables that evoke and maintain it. By shifting the empirical gaze from the static structural morphology of a word to its functional dynamics, Sundberg reoriented the entire clinical assessment process. Language was no longer viewed as a static capacity possessed by the child, but as an active, dynamic repertoire of functional operants emitted in relation to immediate environmental circumstances.

Sundberg’s systematic articulation of the verbal operant as the foundational unit of linguistic analysis had profound clinical ramifications. In conventional speech-language therapy, if an autistic child could repeat the word “water” when asked to say it, label a picture of “water,” and point to a cup of water, clinicians historically assumed the child “knew” the word. Sundberg empirically exposed the fallacy of this assumption. He demonstrated that each of these behaviors belongs to a distinct functional operant class, controlled by entirely separate antecedent conditions and reinforcement mechanisms. The functional analysis of language established that mastering a word in one operant category provides no empirical guarantee that the child can functionally deploy that same word under differing environmental arrangements—a profound insight that completely restructured language instruction paradigms.

2.2 Rigorous Demarcation of Elementary Verbal Operants

Central to Sundberg’s pedagogy and clinical practice is the precise demarcation of Skinner’s elementary verbal operants: the mand, the tact, the echoic, the intraverbal, textual behavior, and transcriptive behavior. Each operant is defined not by its outward physical topography, but strictly by the specific controlling antecedents and consequences that govern its emission. Sundberg meticulously outlined these operant typologies to eliminate the pervasive diagnostic ambiguity found in traditional communicative assessments, providing clinicians with explicit criteria for isolating functional deficits.

The mand represents the foundational operant of functional language acquisition. It is a verbal response evoked by an establishing operation (EO) or motivating operation (MO)—an environmental or physiological state of deprivation, satiation, or aversive stimulation—and maintained by a specific, functionally related reinforcer. If a child is water-deprived, the motivating operation increases the momentary value of water as a reinforcer and evokes the verbal response “water,” which is reinforced specifically by the delivery of water. Sundberg repeatedly demonstrated that the mand is the only verbal operant that directly benefits the speaker by granting access to momentary reinforcers or alleviating aversive conditions, making it the non-negotiable starting point for early language acquisition programs.

Conversely, the tact is a verbal operant evoked by a non-verbal discriminative stimulus (such as an object, action, event, property, or relation) and maintained by generalized conditioned reinforcement, such as social praise or informational acknowledgment. When a child sees a canine and states “dog,” without any momentary deprivation of a dog and without receiving the dog as a consequence, the child has emitted a pure tact. Sundberg clarified that the tact serves to inform the listener about the physical state of the environment, fundamentally contrasting with the mand, which serves to satisfy the speaker’s internal motivating conditions.

The formal verbal operants—the echoic, textual, and transcriptive behaviors—are governed by verbal discriminative stimuli and exhibit specific formal properties. The echoic occurs when a vocal verbal stimulus evokes a matching vocal response characterized by point-to-point correspondence and formal similarity (e.g., hearing “ball” and saying “ball”). Textual behavior involves a visual verbal stimulus evoking a corresponding vocal response with point-to-point correspondence but lacking formal similarity (e.g., seeing the printed letters C-A-T and vocalizing “cat”). Transcriptive behavior encompasses copying text or taking dictation. Finally, the intraverbal operant represents communicative interaction where a verbal stimulus evokes a verbal response that possesses neither point-to-point correspondence nor formal similarity (e.g., someone asking “What do you drink?” and the individual replying “Water”). Sundberg highlighted that intraverbal behavior forms the behavioral substratum of social conversation, thematic clustering, abstract academic discussions, and sequential cognitive reasoning.

2.3 The Critical Role of Motivating Operations (MOs) in Verbal Acquisition

Perhaps no theoretical contribution of Mark Sundberg is more consequential to applied behavior analysis than his operationalization of motivating operations (MOs) within verbal training paradigms. Working alongside Jack Michael, who formally introduced and refined the concept within behavioral literature, Sundberg translated the abstract dynamics of the MO into actionable, clinical mand training protocols. While early behavior analysis had heavily emphasized discriminative stimuli ($S^D$s) and reinforcement mechanics, it routinely conflated stimulus control with motivational states, leading to widespread instructional errors in pediatric intervention.

Sundberg established clear diagnostic boundaries between discriminative stimuli and motivating operations. An $S^D$ is an antecedent stimulus that signals the differential availability of a specific reinforcer based on a past history of reinforcement for that response in the presence of that stimulus. In contrast, an MO alters both the momentary reinforcing effectiveness of a consequence (the value-altering effect) and the momentary frequency, latency, or intensity of all behavior that has previously been reinforced by that consequence (the behavior-altering effect). Sundberg distinguished between unconditioned motivating operations (UMOs)—such as food, water, sleep, oxygen, and temperature extremes, which do not depend on an ontogenetic learning history—and conditioned motivating operations (CMOs), which acquire their motivational properties through individual environmental experiences.

Within applied verbal programs, Sundberg placed special emphasis on the transitive conditioned motivating operation (CMO-T). A CMO-T occurs when an environmental event establishes another stimulus as a momentary reinforcer and evokes the behaviors that have historically obtained that conditioned reinforcer. For example, presenting a child with an un-opened juice box (when the child is thirsty) establishes a straw—which is currently absent—as a highly potent conditioned reinforcer, thereby evoking a mand for “straw.” Sundberg demonstrated that instructional failures in traditional early intervention occurred because instructors were attempting to teach mands in the absence of authentic motivating operations, relying instead on non-verbal prompts (holding up a cookie) and echoic prompts (“Say cookie”). In such flawed paradigms, the response “cookie” was placed under the control of an $S^D$ (the sight of the cookie) or an intraverbal command (“What do you want?”), yielding a pure tact or a prompt-dependent response rather than an authentic mand. Sundberg’s clinical mandates required practitioners to systematically capture natural MOs or engineer contrived CMO-Ts before delivering mand instruction, a paradigm shift that eradicated prompt dependency for hundreds of thousands of learners globally.

3. The Inception and Historical Impact of The Analysis of Verbal Behavior (TAVB)

3.1 Founding the Special Interest Group and Academic Journal

By the late 1970s, despite Skinner’s monumental theoretical framework and the expanding application of operant principles, verbal behavior occupied a marginal, fragmented niche within the broader discipline of behavior analysis. The primary journal of the field, the Journal of Applied Behavior Analysis (JABA), was dominated by studies targeting the deceleration of aberrant behaviors, self-injurious actions, and token economies, rarely engaging with the micro-structural verbal operant taxonomy presented in Skinner’s 1957 text. Recognizing that Skinner’s functional analysis of language risked permanent academic obscurity, Mark Sundberg spearheaded the organizational movement to establish a dedicated scholarly home for verbal behavior research.

In the late 1970s, Sundberg organized like-minded behavioral scholars to form the Verbal Behavior Special Interest Group (VB-SIG) under the auspices of the Association for Behavior Analysis (ABA, later ABAI). In 1979, Sundberg founded The Verbal Behavior Newsletter, serving as its primary typist, editor, and distributor. Operating with minimal institutional funding, Sundberg published essays, conceptual clarifications, and preliminary empirical pilot investigations. By 1982, recognizing the maturation of the science and the critical necessity for a peer-reviewed research vehicle that could withstand academic scrutiny, Sundberg formalized the publication into The Analysis of Verbal Behavior (TAVB). Sundberg served as the founding Editor-in-Chief of TAVB for sixteen consecutive years, personally shepherding the journal through its infancy and establishing its reputation as a rigorous experimental publication.

The emergence of TAVB under Sundberg’s leadership provided an indispensable empirical platform designed to counter the intellectual dominance of Chomskyan cognitive linguistics. For decades, the dominant academic narrative held that Chomsky had dealt a fatal blow to behaviorism in his 1959 critique. Sundberg used TAVB to construct an empirical refutation. The journal systematically published experimental papers demonstrating that Chomsky’s central claims—such as the impossibility of teaching grammar, generative speech, or complex semantics via operant conditioning—were empirically false. Under Sundberg’s editorial oversight, TAVB demonstrated that verbal operant mechanics could directly establish syntax, derived relations, and novel functional repertoires across both neurotypical and neurodevelopmentally delayed cohorts.

3.2 Sustained Research Dissemination and Methodological Rigor

Throughout his sixteen-year tenure as editor and his subsequent decades on its editorial board, Sundberg maintained rigorous methodological standards for The Analysis of Verbal Behavior. The journal became a proving ground for single-case experimental designs—including concurrent multiple-baseline designs across behaviors and participants, multi-element designs, and changing-criterion protocols—applied directly to verbal functional taxons. Sundberg demanded that authors avoid the loose colloquial language of mentalism and maintain strict conceptual adherence to Skinner’s operational definitions. Every study published in TAVB had to isolate the precise variables responsible for verbal acquisition, requiring systematic component analyses, rigorous inter-observer agreement measures, and objective measurement of non-verbal listener behavior.

Sundberg leveraged the journal to address complex, historically intractable communication deficits. TAVB published pioneering investigations into defective intraverbal repertoires, demonstrating how individuals with autism could be guided from simple rote intraverbal associations to multi-layered, conditionally discriminated conversational dialogues. The journal became the primary forum for experimental evaluations of listener responding, echoic repertoire expansion, textual comprehension, and autoclitic manipulation. Sundberg actively bridged the divide between basic human operant laboratories and applied clinical interventions, ensuring that discoveries regarding stimulus equivalence, motivating operations, and joint control were rapidly translated into clinical curricula.

The academic validation of Sundberg’s institutional vision became undeniably evident as the journal evolved. TAVB grew from an independently printed specialty newsletter into an internationally indexed, prestigious academic journal published by Springer Science+Business Media, officially sponsored by ABAI. The journal’s inclusion in major biomedical and behavioral indexing services (such as PubMed Central and PsycINFO) validated Sundberg’s long-term institutional mission: establishing the analysis of verbal behavior as an independent, empirically robust sub-discipline within the global life sciences.

4. Early Collaborative Applied Work: The Assessment of Basic Language and Learning Skills (ABLLS)

4.1 Collaboration with James W. Partington and Clinical Origins

During the 1980s and 1990s, the field of early intensive behavioral intervention for children with autism was heavily dominated by the traditional Lovaas model, an applied behavior analytic paradigm formulated by Ivar Lovaas at UCLA. While the Lovaas model provided groundbreaking evidence that early behavioral intervention could dramatically improve developmental outcomes, its communicative curriculum relied extensively on structural linguistic hierarchies, non-functional receptive identification drills, repetitive vocal imitation, and rigid discrete trial training (DTT) formats. Children taught under these early models frequently developed severe behavioral prompt dependence, robotic vocal intonations, and a profound inability to emit spontaneous mands in the natural environment. Recognizing these systemic clinical deficits, Mark Sundberg initiated a clinical collaboration with James W. Partington to engineer an entirely new assessment and curricular protocol rooted explicitly in Skinnerian verbal operants.

Sundberg and Partington identified that standard standardized tests—such as the Peabody Picture Vocabulary Test or the Vineland Adaptive Behavior Scales—were fundamentally psychometric, normative instruments designed to rank a child relative to peers rather than identify functional environmental deficits. They lacked the micro-level task analyses and functional operant distinctions necessary to design a daily behavioral curriculum. Over years of iterative clinical testing across specialized autism clinics and home-based therapy programs, Sundberg and Partington synthesized direct behavioral observation, criterion-referenced skill tracking, and Skinner’s verbal operants into a coherent assessment architecture.

This collaboration culminated in the monumental 1998 publication of their co-authored curriculum guide, Teaching Language to Children with Autism or Other Developmental Disabilities, accompanied by its criterion-referenced assessment tool, the Assessment of Basic Language and Learning Skills (the ABLLS). The release of the ABLLS represented a watershed moment in autism intervention. For the first time, clinicians, behavior analysts, and speech-language pathologists were provided with a comprehensive, visually tracked assessment protocol that systematically mapped a child’s linguistic, academic, self-help, and social repertoires against the functional categories of verbal behavior.

4.2 Pedagogical and Curricular Paradigms of the 1998 Model

The publication of the ABLLS and its companion text fundamentally restructured behavioral intervention methodologies worldwide. Central to Sundberg and Partington’s curricular philosophy was the operationalization of Natural Environment Training (NET) alongside structured, table-top Intensive Teaching Trials (ITT). Rather than confining language intervention to sterile, highly structured clinical settings characterized by repetitive massed trials, Sundberg and Partington argued that verbal skills must be introduced and captured within the child’s natural motivational contexts. The NET paradigm explicitly mandated that the child’s immediate, shifting motivating operations should dictate instructional sequences, transforming daily activities—such as snack time, playground recreation, and toy manipulation—into high-density learning environments for manding and naturalistic tacting.

Furthermore, the 1998 curriculum established a sophisticated operational framework for integrating alternative and augmentative communication (AAC) modalities. In direct contrast to the prevailing therapeutic assumptions of the time, which often delayed functional communication intervention in the futile pursuit of vocal speech, Sundberg and Partington established clear empirical decision trees for introducing manual sign language (topography-based communication) or picture exchange systems (selection-based communication). The manual demonstrated that introducing manual signs did not inhibit vocal emergence; rather, by utilizing the motor imitation repertoire and pairing manual signs with vocal verbal stimuli, the acquisition of sign language consistently accelerated vocal phonation and functional language production.

The ABLLS manual was rapidly adopted by major school districts, early autism intervention agencies, and developmental clinics across North America and Europe. It established a shared, technical vocabulary among behavior analysts, educators, and pediatric therapists. However, as the field continued to mature, scientific divergences emerged. While Partington focused on refining the ABLLS into its subsequent edition (the ABLLS-R), Sundberg identified critical developmental limitations within the original 1998 instrument. He observed that the ABLLS lacked explicit developmental milestone calibration against neurotypical child development, contained overlapping curricular metrics, and omitted crucial evaluations of language acquisition barriers. These developmental observations ultimately compelled Sundberg to pursue an independent trajectory, culminating in the design of the VB-MAPP.

5. Conceptual Architecture of the VB-MAPP

5.1 Origins, Theoretical Motivation, and Developmental Benchmarking

Following the success of the ABLLS, Mark Sundberg recognized that behavior analytic language interventions risked isolating themselves from the vast, empirically robust body of mainstream child development research. Traditional behavioral curricula had historically operated under an arbitrary linear sequence of instructional targets that occasionally diverged from typical human ontogeny. For example, behavioral programs often taught children with autism to identify colors, shapes, and complex categorical abstractions before the child had even developed stable one-word echoic, mand, or basic generalized tact repertoires. Sundberg argued that for a behavioral language intervention to achieve true developmental proportionality and functional validity, it must align with the natural, neurotypical sequence of infant and early childhood language acquisition.

Sundberg spent a decade observing, coding, and measuring the communicative repertoires of typically developing infants and young children alongside clinical populations. He sought to identify the specific ages at which typical children acquire critical linguistic thresholds, such as the emergence of the first spontaneous mands, the explosion of tacting repertoires, the formation of multi-component listener discriminations, and the onset of generative intraverbal dialogues. By synthesizing these empirical normative benchmarks with the conceptual taxonomy of Skinner’s Verbal Behavior, Sundberg formulated an integrated, developmental-behavioral model. His overarching theoretical premise was that while the sequence of communicative milestones is developmentally universal, the functional mechanism responsible for traversing that sequence is entirely operant—governed by stimulus control, motivating operations, and consequence histories.

This monumental effort culminated in 2008 with the publication of the Verbal Behavior Milestones Assessment and Placement Program (the VB-MAPP). The VB-MAPP was designed as an all-encompassing, criterion-referenced assessment, tracking system, and curriculum placement guide engineered specifically for individuals with autism and developmental disabilities. The assessment was calibrated across a four-year developmental timeline (0 to 48 months of neurotypical chronological functioning), partitioned into three discrete developmental tiers. The publication of the VB-MAPP firmly established Sundberg as the undisputed global authority on the clinical implementation of verbal behavior.

5.2 The Tripartite Structural Framework of the Assessment

The structural framework of the VB-MAPP is divided into three developmentally indexed tiers, each encapsulating critical operational milestones that mirror typical developmental maturation while remaining fully anchored in operant principles. The Milestones Assessment evaluates 170 measurable behavioral benchmarks across sixteen distinct skill domains, enabling clinicians to visually chart a learner’s profile against normal developmental trajectories.

Level 1 (0 to 18 Months): Level 1 is engineered to evaluate the foundational roots of functional communication. Within this initial tier, the assessment concentrates intensively on basic, unprompted mands, echoic vocal approximations (quantified via the sub-test adapted from the Early Echoic Skills Assessment by Barbara E. Esch), gross and fine motor imitation, listener responding (such as attending to vocal stimuli, locating objects upon verbal command, and identifying primary items in the visual field), and early tacting of familiar environmental items. Level 1 deliberately avoids complex linguistic demands, ensuring that the primary functional relations—especially the mand and echoic repertoires—are firmly conditioned before higher-order demands are introduced.

Level 2 (18 to 30 Months): Level 2 captures the rapid linguistic explosion that characterizes late toddlerhood. Within this developmental bracket, the assessment tracks the expansion of the tact repertoire from basic single-noun vocalizations to multi-component noun-verb, verb-noun, and adjective-noun combinations. Crucially, Level 2 introduces the assessment of Listener Responding by Feature, Function, and Class (LRFFC). LRFFC assesses a learner’s ability to identify a non-verbal stimulus when provided with descriptive features (“Find the one with wheels”), functional applications (“Which one do you cut with?”), or categorical classes (“Show me the animal”). Concurrently, Level 2 tracks the emergence of foundational intraverbal frames (e.g., song completions, animal sounds, basic personal information) and early social interaction with peers.

Level 3 (30 to 48 Months): Level 3 encompasses the acquisition of advanced, complex linguistic repertoires, social conversational networks, and emerging pre-academic skills. At this developmental level, the learner is assessed on generative intraverbal responding involving conditional discriminations, multi-clause conversational exchanges, and the deployment of primary autoclitics (linguistic devices that modify the listener’s reaction to primary verbal operants). Level 3 also evaluates early literacy and numeracy skills, such as reading basic textual stimuli, taking dictation, copying geometric and typographical figures, and matching items based on abstract mathematical relations. Sundberg created standardized administration guidelines, explicit baseline testing rules, and an intuitive longitudinal visual tracking grid, enabling practitioners to track a child’s progress across multiple assessments over several years.

6. The VB-MAPP Assessment Protocols: Barriers, Transition, and Supporting Sub-tests

6.1 The Barriers Assessment: Identifying Pathological and Behavioral Impediments

One of the most clinically transformative components of the VB-MAPP system is the VB-MAPP Barriers Assessment. While developmental assessments historically focused exclusively on what a child can do, Sundberg recognized that language acquisition in individuals with autism is uniquely impeded by severe learning barriers, defective operants, and interfering behavioral topographies. A child may possess a high volume of rote tacts, but if that child is characterized by severe prompt dependency, rigid instructional non-compliance, or persistent verbal scrolling, standard intervention plans will predictably fail. The Barriers Assessment was designed to evaluate twenty-four specific pathological impediments to learning and language acquisition.

The twenty-four barriers include both overt behavioral challenges and subtle, defective communicative repertoires. These encompass: instructional control problems; defective mands (e.g., mands that only occur with physical prompts or mands accompanied by severe problem behaviors); defective tacts (such as overgeneralized or undergeneralized stimulus control); defective echoic repertoires (including immediate or delayed echolalia and non-functional verbal perseveration); defective intraverbal behavior; defective visual matching skills; and prompt dependency. Additionally, the Barriers Assessment systematically scores phenomena such as scrolling (emitting a rapid sequence of topographies until reinforcement is accidentally contacted), hyper-selectivity (attending to a single, irrelevant micro-feature of an instructional stimulus), defective generalization, failure to articulate clearly, self-injurious behavior, and sensory self-stimulatory behaviors that compete with instructional engagement.

Each barrier is scored on a standardized Likert scale ranging from 0 (no learning impediment present) to 4 (severe, debilitating learning barrier requiring immediate, intensive behavior-analytic remediation). Sundberg established an explicit, direct linkage between the severity score of specific barriers and specialized instructional programming. For example, if a child scores a 4 on “Prompt Dependency,” the instructional priority shifts immediately away from introducing new tact targets and toward systematic prompt-fading protocols, transfer-of-stimulus-control procedures, and the elimination of extraneous instructor prompts. In this manner, Sundberg ensured that behavior reduction plans were never functionally detached from the child’s verbal intervention curriculum.

6.2 The Transition Assessment: Gauging Educational Restrictiveness and Placement

A perennial, high-stakes challenge within special education and developmental pediatrics involves determining the educational placement of children with autism: deciding whether a child should be placed in an intensive, segregated behavioral clinic, a self-contained special education classroom, an integrated resource-supported setting, or a fully inclusive general education classroom. Historically, these educational decisions were driven by political considerations, subjective clinical impressions, or psychometric IQ scores that bore little direct relevance to a child’s capacity to navigate a real-world classroom environment. To resolve this dilemma, Sundberg conceptualized and operationalized the VB-MAPP Transition Assessment.

The Transition Assessment establishes an objective, empirical metric designed to gauge a learner’s readiness to transition into a less restrictive educational environment (LRE). The instrument evaluates eighteen distinct transition dimensions, synthesizing milestone proficiency, barrier reduction, and specific behavioral capabilities critical for collective learning environments. These dimensions include: overall Milestones Assessment score; overall Barriers Assessment score; the presence of negative behaviors and tantrums; classroom routines and group learning skills; social behavior and social play; independent academic work repertoires; generalization of skills across time, settings, and instructors; learning in a format that utilizes group instruction; retention of learned skills; resistance to change and behavioral flexibility; and independent toilet training and self-care skills.

By quantifying these disparate behavioral indicators onto a single unified tracking rubric, Sundberg provided multidisciplinary teams, clinical directors, and Individualized Education Program (IEP) teams with an empirically defensible tool for educational placement. The Transition Assessment prevents two catastrophic clinical mistakes: placing an unprepared child into an unsupportive, highly chaotic general education classroom where the child experiences social isolation and academic failure; or unnecessarily confining a highly capable, self-directed verbal learner within a restrictive, segregated clinical setting that limits exposure to neurotypical linguistic and social models.

6.3 The Task Analysis and Skills Grid: Micro-Level Skill Deconstruction

While the 170 milestones within the VB-MAPP provide broad, developmentally indexed targets, they intentionally represent large, macroscopic behavioral thresholds. For children presenting with severe intellectual deficits, profound apraxia, or significant learning barriers, jumping directly from one milestone to the next can prove impossible without systematic scaffolding. To bridge this clinical divide, Sundberg developed the comprehensive VB-MAPP Task Analysis and Skills Grid, a companion instrument that micro-deconstructs each global milestone into a granular, successive continuum of enabling behavioral targets.

The Task Analysis provides clinicians, special educators, and registered behavior technicians with an item-by-item roadmap for daily lesson planning. For instance, rather than simply requiring a child to acquire Milestone 5 in Listener Responding (selecting five familiar items from a field of four stimuli), the Task Analysis delineates the precise intermediary developmental steps: orienting toward the instructor’s vocal stimulus, scanning visual arrays of two items, scanning three items, selecting items in the natural environment, discriminating between dissimilar objects, and overcoming spatial position biases. This granular sequencing ensures that prerequisites are systematically mastered before advanced functional demands are imposed.

Crucially, the Task Analysis serves as an essential diagnostic diagnostic tool for differentiating authentic generalized verbal operants from “splinter skills.” In clinical intervention, learners with autism frequently display splinter skills—memorized, hyper-specific behavioral repertoires that collapse the moment instructional stimuli, room conditions, or communicative partners are altered. By requiring data collection across the micro-steps delineated in the Task Analysis, Sundberg’s framework forces clinicians to engineer stimulus and response generalization into daily teaching trials, verifying that operants remain stable across diverse operational conditions.

7. Operant Analysis of Complex Linguistic Phenomena: The Intraverbal Repertoire

7.1 Taxonomy of Intraverbal Relations and Deficits in Autism Spectrum Disorders

Among the most cognitively sophisticated and clinically challenging domains within Skinner’s 1957 taxonomy is the intraverbal operant. Defined as verbal behavior evoked by an antecedent verbal stimulus where the response does not possess point-to-point correspondence or formal similarity with the stimulus, intraverbal behavior constitutes the foundation of human conversation, academic dialogue, sequential mathematical computation, and internal cognitive thought. Throughout his career, Mark Sundberg conducted foundational conceptual analyses and empirical investigations to demystify intraverbal relations, categorizing how intraverbal stimulus control develops in neurotypical children and why it remains so profoundly impaired in individuals diagnosed with autism spectrum disorder.

Sundberg distinguished between simple intraverbal chains and complex, conditionally discriminated intraverbal relations. Simple intraverbal chains are typically learned via continuous rote pairing; they involve direct stimulus-response linkages where one word immediately evokes the next (e.g., saying “peanut butter and…” evokes “jelly,” or vocalizing “Ready, set…” evokes “go”). While these simple chains represent essential developmental building blocks, individuals with autism frequently become trapped within this mechanical level of responding. Their intraverbal repertoires are characterized by rigid, stereotyped associations, profound echolalia, and an inability to adapt to shifting conversational contexts.

The critical evolutionary hurdle in human language, as articulated by Sundberg, involves the mastery of convergent and divergent intraverbal stimulus control under conditional discrimination. In convergent intraverbal responding, multiple antecedent verbal stimuli combine to exert joint stimulus control over a single verbal response. For example, in the question, “What is a large gray animal that has a trunk?”, the verbal response “elephant” is not controlled by any single word in isolation. The word “large” alone could evoke “building”; “gray” alone could evoke “cloud”; “animal” alone could evoke “dog”; and “trunk” alone could evoke “car.” Only when the speaker’s vocal behavior is conditionally constrained by the confluence of all four verbal stimuli simultaneously can the correct response “elephant” emerge. Sundberg’s empirical research demonstrated that intraverbal deficits in autism stem precisely from an inability to attend to and process compounding verbal discriminative stimuli, leading to severe stimulus overselectivity, thematic perseveration, and off-topic scrolling.

7.2 Intraverbal Assessment Protocols and Empirical Investigations

To systematically diagnose and remediate these complex conversational deficits, Sundberg pioneered the formulation of specialized, granular diagnostic sub-tests, culminating in the development of the 80-item and 300-item Intraverbal Subtests. These assessment protocols were engineered to parse the precise micro-structural deficits present in an individual’s verbal repertoire, mapping intraverbal capabilities across an escalating continuum of linguistic and cognitive complexity.

The intraverbal assessment hierarchy designed by Sundberg methodically isolates distinct categories of verbal stimulus control. It progresses through the following operational strata:

• Category-to-Item Associations: Identifying members of a class upon verbal presentation (e.g., “Name some fruits”).
• Item-to-Category Associations: Naming the broader classification upon verbal presentation of an exemplar (e.g., “A shirt is a type of…”).
• Function-to-Item and Item-to-Function Relations: Discriminating what objects do and what tools are used for specific environmental tasks (e.g., “What do you do with a broom?” versus “What do you use to sweep the floor?”).
• Feature-to-Item and Item-to-Feature Relations: Analyzing components, physical properties, and adjectives (e.g., “What has whiskers?” versus “Tell me what a cat looks like”).
• Compound Verbal Discriminative Stimuli ($V S^D$): Responding to conditional sentences containing modifying prepositions, temporal markers, or conditional clauses (e.g., “What is something hot that you eat with a spoon?”).
• Negation and Exclusionary Intraverbal Frames: Responding accurately to frames involving negative operators (e.g., “Name a vehicle that does not have wheels,” or “What do you wear when it is not cold?”).
• Advanced WH-Questions: Generating contextually appropriate responses to compounding Who, What, Where, When, and Why sequences where antecedent verbal markers demand flexible perspective-taking and temporal reasoning.

Sundberg’s empirical studies into intraverbal error patterns revealed that clinical failures in teaching conversation to autistic individuals frequently resulted from therapists attempting advanced WH-question training while the child still lacked basic noun-verb conditional control. His publications provided explicit teaching methodologies for establishing generative intraverbal repertoires, emphasizing the systematic fading of visual tact prompts into intraverbal prompts, the dynamic rotation of distracter questions, and the contrivance of varied linguistic frames to prevent scripted, memorized responding.

8. Advanced Skinnerian Formulations: Multiple Control, Autoclitics, and Joint Control

8.1 Multiple Control in Functional Language Acquisition

A fundamental hallmark of Mark Sundberg’s scholarship is his deep theoretical and applied operationalization of Skinner’s concept of multiple control. In traditional structural psycholinguistics, speech is frequently treated as an isolated, linear event governed by internal semantic decisions. Skinner, however, observed that human verbal behavior is almost never the product of a single, isolated antecedent variable. Rather, verbal behavior is perpetually governed by multiple environmental variables operating simultaneously on the speaker. Sundberg elevated this concept into a cornerstone of behavioral pedagogical design, explicating both convergent and divergent multiple control.

Convergent multiple control occurs when multiple distinct antecedent variables combine to evoke a single verbal response topography. For instance, when a child in a classroom sees a picture of an ocean, hears the teacher say “Where do sharks live?”, and feels a momentary interest in marine life, the resulting vocalization “In the ocean” is not maintained by a single environmental force. It is evoked through the convergence of a non-verbal stimulus (the picture), a verbal stimulus (the question), an intraverbal history, and a motivating operation. Sundberg demonstrated that achieving natural, spontaneous speech in individuals with autism requires behavior analysts to intentionally construct interventions characterized by convergent multiple control, gradually fading out intrusive prompts while allowing subtle environmental and motivational stimuli to maintain communicative responding.

Conversely, divergent multiple control occurs when a single environmental stimulus exerts functional control over multiple distinct response topographies. For instance, the sight of a fire can evoke the tact “Fire!”, the mand “Call 911!”, the intraverbal “It’s too hot,” or the emotional respondent reaction of physiological arousal. Sundberg underscored that learners with developmental delays typically suffer from severely constricted divergent control: when presented with a stimulus, they emit a single, highly conditioned, repetitive response. Sundberg’s instructional curricula introduced protocols designed specifically to condition divergent verbal repertoires, teaching children to emit varied tacts, mands, and intraverbals in response to a single non-verbal or verbal event. This methodological focus directly disrupted the rigid, robotic communication patterns historically produced by mechanical discrete trial training.

8.2 Autoclitic Processes and Syntactic Organization

One of the most complex, formidable chapters of Skinner’s 1957 work is dedicated to the autoclitic—a verbal operant that depends upon, modifies, and is conditioned by other verbal behavior emitted by the speaker. Skinner derived the term from “leaning” (autoclitic: behavior that leans on other behavior). Because of its conceptual density, early applied behavior analysts routinely avoided the topic. Mark Sundberg was instrumental in demystifying the autoclitic, translating it into actionable clinical and educational teaching hierarchies that explained the structural and syntactic organization of human speech from a strictly operant perspective.

Sundberg operationalized autoclitic repertoires for clinical intervention, deconstructing them into functional categories:

• Descriptive Autoclitics: Verbal behavior conditioned upon the speaker’s own ongoing behavioral state or the certainty of their tact (e.g., “I think that is a dog,” versus “I see a dog,” or “I guarantee that will happen”). The phrases “I think,” “I see,” and “I guarantee” do not refer to external objects; they inform the listener about the precise strength and source of the speaker’s primary verbal behavior.
• Qualifying Autoclitics: Verbal behavior that modifies the intensity or direction of the primary operant, most notably negation (e.g., “That is not candy,” where the word “not” fundamentally alters the listener’s upcoming behavior relative to the primary tact “candy”).
• Quantifying Autoclitics: Verbal stimuli that specify the numerical or structural scope of the primary response (e.g., “all,” “some,” “few,” “many”).
• Relational and Grammatical Autoclitics: Verbal behavior involving syntactic structures, inflections, prepositions, and grammatical ordering (e.g., the difference between “The boy bit the dog” and “The dog bit the boy”). Sundberg demonstrated that syntax is not an innate cognitive template, but a sequence of autoclitic framing shaped by the listener environment to ensure precise communicative consequences.

Sundberg’s clinical guidance warned practitioners against premature autoclitic training. He noted that therapists frequently attempted to teach children with autism complete sentences (such as demanding the carrier phrase “I want chocolate please” instead of simply “chocolate”) before the child had even developed stable, primary mand repertoires. Sundberg proved that enforcing robotic autoclitic frames (“I want…”) before primary operants are mastered generates prompt dependency, obscures authentic motivating operations, and impedes communicative spontaneity. His protocols mandated that primary operants must be robustly established before secondary, autoclitic behaviors are systematically layered onto a child’s linguistic output.

8.3 Joint Control in Complex Cognitive and Communicative Tasks

In analyzing how humans execute complex cognitive tasks, such as delayed matching-to-sample, following complex multi-step instructions, and recalling sequential stimuli, cognitive psychology routinely invokes hypothetical constructs such as “working memory,” “executive functioning,” and “central executive processing.” Mark Sundberg, drawing upon the pioneering experimental work of Barry Lowenkron, championed the behavioral concept of joint control as an empirical, operant alternative to these mentalistic explanations.

Joint control is technically defined as the discrete emergence of a verbal or non-verbal response that is evoked by the convergence of two distinct, independent sources of stimulus control operating simultaneously upon the speaker. Lowenkron and Sundberg demonstrated that complex, delayed listener responding depends upon a continuous behavioral chain involving mediating verbal behavior. For instance, when an individual is asked to “Go to the supply closet and get the red, stapled document,” a considerable temporal delay occurs between the auditory instruction and the physical selection of the object. Cognitive models attribute this retrieval to working memory. Sundberg and Lowenkron proved that the human listener bridges this temporal gap via an echoic or self-directed intraverbal response: the individual continuously rehearses “red, stapled document… red, stapled document.” Upon entering the supply closet, the individual scans the visual stimuli until an object evokes a tact that matches the ongoing, self-echoic verbal rehearsal. The momentary convergence of the self-maintained vocal stimulus and the visual discriminative stimulus exerts joint control, evoking the final, accurate selection response.

Sundberg integrated joint control paradigms directly into advanced language curricula for children with autism who presented with severe deficits in auditory processing, instructional retention, and problem-solving. By teaching children to systematically emit self-echoic rehearsal behavior and visually scan complex arrays until joint control is achieved, Sundberg provided clinicians with an empirical technology for teaching what traditional educational psychology had previously classified as unteachable executive functioning deficits.

9. Instructional Methodologies: The Natural Environment Training (NET) Paradigm

9.1 Natural Environment Training (NET) versus Intensive Teaching Trials (ITT)

The institutionalization of applied behavior analysis within pediatric autism intervention was largely driven by the discrete trial training (DTT) methodology pioneered in the late twentieth century. Characterized by seated table-top instruction, rapid trial presentation, arbitrary reinforcement (e.g., delivering an edible for pointing to a flashcard), and strict stimulus control, DTT proved effective for establishing basic discriminative repertoires. However, serious clinical limitations quickly became apparent: children taught exclusively via rigid discrete trials struggled to generalize skills to everyday settings, demonstrated severe prompt dependency, and rarely engaged in spontaneous, self-initiated functional communication. Mark Sundberg served as one of the most vocal, influential architects of the pedagogical paradigm shift known as Natural Environment Training (NET).

Sundberg did not advocate for the wholesale elimination of table-top instruction; rather, he delineated an explicit behavioral and structural dichotomy between Intensive Teaching Trials (ITT) and Natural Environment Training (NET), arguing that an effective clinical program must integrate both modalities systematically. The differences between the two paradigms, as articulated by Sundberg, are rooted in their distinct motivating, antecedent, and consequential mechanics:

Sundberg demonstrated that NET is the clinically mandatory instructional vehicle for establishing authentic, spontaneous mand repertoires. In NET, the clinician continuously tracks the child’s shifting focus, capturing momentary states of deprivation or contriving environmental disruptions (transitive motivating operations) that render specific items or actions instantly reinforcing. By embedding teaching trials into the natural flow of daily routines, Sundberg proved that children with autism could acquire high rates of unprompted, spontaneous communication that generalized effortlessly across their homes, schools, and communities.

9.2 Errorless Learning and Prompt Fading Paradigms in Verbal Interventions

A critical technical contribution made by Sundberg to everyday instructional design was the refined application of errorless learning and systematic transfer-of-stimulus-control procedures within verbal intervention programs. Traditional educational paradigms often relied on trial-and-error teaching, wherein an instructor presented a demand, permitted the learner to guess or emit incorrect responses, and then provided corrective feedback. Sundberg demonstrated that for individuals with severe language and cognitive deficits, trial-and-error procedures are highly detrimental: errors provoke emotional and aggressive outbursts, generate behavioral avoidance of instructional settings, and rapidly stabilize incorrect response topographies through erroneous reinforcement histories (such as verbal scrolling).

To eliminate these pedagogical pitfalls, Sundberg advanced errorless learning protocols characterized by immediate, antecedent prompting followed by systematic time delays. When introducing a novel verbal target, the instructor does not provide an opportunity for the learner to fail. Instead, the antecedent discriminative stimulus or motivating operation is immediately paired with a full, controlling prompt (such as an immediate echoic prompt for vocal learners or a full physical prompt for signers). Once the correct response topography is successfully emitted and reinforced, the instructor rapidly executes a transfer of stimulus control trial. Through precise time-delay protocols, the prompt is faded (e.g., introducing a 2-to-3 second latency before prompt delivery), transferring stimulus control entirely to the naturally occurring verbal or non-verbal $S^D$ or momentary motivating operation.

Sundberg also developed comprehensive behavioral strategies for remediating verbal scrolling—a pervasive error pattern in which a child cycles through an inventory of previously reinforced words (e.g., saying “cup… juice… ball… red”) in the hope that one will satisfy the instructor. Sundberg identified scrolling as an artifact of faulty stimulus control, typically caused by instructors accepting partially prompted or delayed responses during trial-and-error teaching. His error-correction protocols mandated the immediate interruption of scrolling, the introduction of a neutral distracter trial to clear the vocal auditory channel, and the re-presentation of the original instructional antecedent paired with an immediate, errorless prompt to re-establish clean, un-scrolled stimulus control.

10. Selection of Communicative Modalities: Sign Language versus Alternative AAC Systems

10.1 Topography-Based versus Selection-Based Verbal Systems

One of the most consequential, mathematically rigorous conceptual papers in the history of behavior analysis was published by Mark Sundberg and Jack Michael in 2001, examining the behavioral distinctions between topography-based and selection-based verbal systems. For decades, speech-language pathologists, assistive technology specialists, and behavior analysts had engaged in heated clinical debates regarding which alternative communication modality should be selected for non-vocal children with autism: manual sign language, picture selection systems (such as the Picture Exchange Communication System, or PECS), or electronic speech-generating devices (SGDs). The prevailing professional decisions were largely driven by subjective preferences, institutional traditions, or mistaken assumptions regarding cognitive capability. Sundberg and Michael resolved this controversy by subjecting communicative modalities to an exhaustive operant functional analysis.

Sundberg and Michael established a profound, permanent distinction between two fundamentally different response classes:

• Topography-Based Verbal Behavior: In topography-based communication, each verbal response involves a uniquely differentiated muscular movement or physical topography. Vocal speech is the preeminent example: saying “apple” requires a radically different muscular and acoustic configuration than saying “book.” Manual sign language is entirely topography-based: the manual sign for “apple” involves a unique set of motor movements, handshapes, and spatial coordinates that bear no physical similarity to the manual sign for “book.”
• Selection-Based Verbal Behavior: In selection-based communication, the motor topography emitted by the speaker is fundamentally identical regardless of the target item; the communicative distinction resides entirely in which external stimulus is selected from an array. When a child utilizes an iPad, a communication binder, or a picture board, the physical response across all responses consists of pointing to, touching, or physically handing over a laminated icon. The motor act of selecting a picture of “apple” is virtually indistinguishable from selecting a picture of “book.”

Through this behavioral dissection, Sundberg and Michael demonstrated the profound cognitive and behavioral processing burdens inherent to selection-based communication. For a child to emit a selection-based mand, the child must: scan a visual array of multiple symbols; maintain an internal conditional discrimination regarding what item is momentarily desired; visually discriminate the correct icon from competing distracters; physically execute the selection topography; and ensure the listener observes the selection. If the required picture is missing from the communication board, the mand cannot be emitted. In stark contrast, topography-based verbal behavior (manual sign language) requires no external scanning array, involves direct motor production, can be emitted anywhere instantly, and relies on an internal behavioral repertoire that allows for rapid, seamless motor chaining and immediate response generalization.

10.2 Clinical Decision-Making Algorithms for Modality Selection

The theoretical superiority of topography-based communication articulated by Sundberg and Michael was systematically tested in clinical environments, yielding an objective clinical decision-making algorithm for modality selection in non-vocal populations. While Sundberg maintained a strong scientific preference for vocal speech as the primary communicative topography, he established explicit behavioral prerequisites to determine when a child should transition immediately to manual sign language versus selection-based AAC.

Sundberg outlined that before choosing an augmentative communication modality, the clinical team must rigorously assess the child’s motor imitation repertoire. If a non-vocal child possesses strong, rapid gross and fine motor imitation capabilities, manual sign language is almost invariably the most efficient, neurologically compatible communicative modality to introduce. Clinical trials conducted by Sundberg and his colleagues repeatedly revealed that children taught via manual sign language acquired spontaneous mands at dramatically faster rates, demonstrated significantly lower response latencies, and exhibited far higher rates of vocal emergence compared to children constrained to selection-based picture systems. The physical execution of manual motor movements shares neurological pathways with vocal motor control; pairing manual signing with vocal speech models repeatedly triggered spontaneous vocal imitation in previously non-vocal children.

However, Sundberg was an exceptionally pragmatic clinician. He recognized the ecological and environmental limitations of manual sign language: the broader community, extended family members, and general education peers rarely understand sign language. Consequently, Sundberg formulated operational guidelines for tailoring modality selection to the individual’s total developmental profile. If a child presents with profound motor dyspraxia, severe fine-motor apraxia, or physical paralysis that permanently precludes the acquisition of differentiated manual signs, selection-based augmentative communication (PECS or dynamic speech-generating devices) is fully warranted. Furthermore, for advanced learners, Sundberg advocated for hybrid models: utilizing sign language for fast, spontaneous natural environment manding while concurrently training speech-generating electronic devices to facilitate communication within broader, non-signing community environments.

11. Academic Critiques, Theoretical Debates, and Comparative Paradigms

11.1 The Dialectic Between Relational Frame Theory (RFT) and Skinnerian Verbal Behavior

As the functional analysis of verbal behavior expanded throughout the late 1990s and 2000s, an intense, fundamental theoretical schism erupted within the radical behavioral community itself. While Sundberg and his traditional Skinnerian contemporaries were institutionalizing the elementary verbal operants, a post-Skinnerian paradigm known as Relational Frame Theory (RFT)—spearheaded by Steven C. Hayes, Dermot Barnes-Holmes, and their associates—emerged to directly challenge Skinner’s 1957 model. RFT proponents asserted that Skinner’s functional analysis was inherently limited, descriptive, and insufficient for explaining the generative nature of human language, abstract cognitive reasoning, and advanced symbolic metaphors.

The core of the RFT critique centered on the concept of derived relational responding. RFT asserted that human language is governed by arbitrarily applicable relational responding—the capacity of human beings to relate stimuli without direct conditioning histories (e.g., mutual entailment, combinatorial entailment, and the transformation of stimulus functions). Proponents of RFT argued that Skinner’s elementary operants relied excessively on direct reinforcement histories, failing to account for how children rapidly acquire vast networks of relational understanding without explicit training on every single contingency. This critique led to the development of alternative assessment and intervention systems, most notably Mark R. Dixon’s PEAK Relational Training System, which sought to integrate derived relational responding into pediatric autism curricula.

Mark Sundberg mounted a formidable, theoretically robust intellectual defense of Skinner’s taxonomy against the post-Skinnerian RFT movement. Sundberg argued that while derived relational responding and stimulus equivalence are genuine empirical phenomena, they do not invalidate or supersede Skinner’s elementary verbal operants; rather, Skinner’s operants constitute the essential, non-negotiable developmental precursors upon which all complex derived relations are ultimately constructed. Sundberg demonstrated empirically that a child cannot successfully engage in relational framing, perspective-taking, or abstract derived responding if the child does not possess a solid foundation of directly reinforced mands, generalized tacts, and conditionally discriminated intraverbals. He cautioned that attempting to teach advanced relational frames to individuals who still display severe deficits in Level 1 and Level 2 VB-MAPP operants is developmentally catastrophic, leading to instructional fragmentation and behavioral frustration. Modern behavioral science has increasingly moved toward an empirical synthesis, recognizing that the VB-MAPP and RFT-based systems occupy complementary stages along an extensive developmental continuum.

11.2 Methodological and Psychometric Appraisals of the VB-MAPP

As the VB-MAPP achieved widespread international adoption across thousands of school districts, state developmental agencies, and global autism centers, it inevitably attracted rigorous psychometric scrutiny from educational researchers, speech-language scholars, and mainstream developmental psychologists. The primary methodological critique leveled against the VB-MAPP centered on its status as a criterion-referenced behavioral instrument rather than a norm-referenced, standardized psychometric test. Psychometricians noted that the VB-MAPP lacked the massive, stratified normative standardization samples, standardized developmental quotients (DQs), and comparative percentile rankings characteristic of traditional psychological batteries such as the Bayley Scales of Infant and Toddler Development or the Mullen Scales of Early Learning.

Furthermore, early independent empirical evaluations of the VB-MAPP highlighted vulnerabilities regarding inter-rater reliability. Because several milestone criteria permit clinicians to score items based on direct testing, formal observation, or historical caregiver report, critics asserted that subjective assessor bias could compromise measurement precision across different therapeutic agencies. Some academic researchers also challenged the empirical boundaries of the age-bracketed milestones, questioning whether the sequence of verbal acquisition observed in neurotypical children could be mapped onto individuals presenting with severe biological neurodevelopmental anomalies.

Sundberg and his research associates systematically addressed these psychometric appraisals, publishing substantial reliability and validity documentation. Sundberg defended the foundational epistemological divergence between psychometric norm-referenced testing and behavioral criterion-referenced assessment. Standardized psychometric tests are deliberately engineered to rank individuals along a bell-shaped curve; they are inherently incapable of guiding daily curricular interventions because they do not evaluate functional environmental relations. In sharp contrast, the VB-MAPP was designed specifically as an idiographic, criterion-referenced instructional roadmap. Sundberg demonstrated that when administered by adequately trained Board Certified Behavior Analysts (BCBAs), the VB-MAPP exhibits remarkably high construct validity, excellent inter-rater reliability, and exceptional criterion-related validity. The ongoing field-testing and continuous operational refinements spearheaded by Sundberg have permanently validated the instrument as an indispensable empirical tool for applied behavioral intervention.

12. Legacy, Global Influence, and the Future of Verbal Behavior (1950–Present)

12.1 Institutional Impact, Authorship, and Professional Recognition

The cumulative impact of Mark L. Sundberg’s career spans more than five decades, representing one of the most prolific and transformative legacies in the history of behavior analysis and special education. Through an extraordinary volume of peer-reviewed empirical papers, foundational textbooks, edited volumes, and international keynote addresses, Sundberg elevated Skinner’s 1957 conceptual masterpiece from academic obscurity into an empirical, clinically indispensable global discipline. His foundational texts—including Teaching Language to Children with Autism or Other Developmental Disabilities (1998) and the VB-MAPP: Verbal Behavior Milestones Assessment and Placement Program (2008)—have become standard university textbooks and essential operational manuals across the behavioral sciences.

The global footprint of Sundberg’s scholarship is unprecedented in scope. The VB-MAPP has been translated into dozens of languages, including Spanish, French, Italian, Chinese, Russian, Arabic, Polish, and Portuguese, driving systemic reforms in autism intervention across North America, South America, Europe, Asia, and the Middle East. School districts and government ministries across the globe have formally incorporated the VB-MAPP into their special education frameworks, permanently displacing outdated psychometric models in favor of individualized, functional language programming. Through his leadership within ABAI, his sixteen-year stewardship of The Analysis of Verbal Behavior, his executive contributions to the B. F. Skinner Foundation, and his continuous direct mentorship, Sundberg has trained and inspired generations of Board Certified Behavior Analysts (BCBAs) who carry forward his standard of conceptual precision.

In recognition of his monumental contributions to the science of human behavior and developmental intervention, Dr. Sundberg has been universally honored by the scientific community. He has been the recipient of prestigious lifetime achievement awards, distinguished service honors, and scientific dissemination recognitions from the Association for Behavior Analysis International (ABAI), the California Association for Behavior Analysis (CalABA), the New York State Association for Behavior Analysis (NYSABA), and numerous international behavioral federations. These formal recognitions solidify his status alongside his mentor Jack Michael and B. F. Skinner as one of the enduring architects of modern behavioral science.

12.2 Ongoing Trajectories and Future Horizons in the Science of Verbal Behavior

As the science of verbal behavior enters the middle of the twenty-first century, Mark Sundberg’s intellectual architecture continues to dictate the research priorities of contemporary behavior analysis. Far from a static historical framework, the analysis of verbal behavior is rapidly expanding into innovative empirical frontiers, actively synthesizing behavioral taxonomies with insights from cognitive neuroscience, developmental linguistics, and cutting-edge educational technologies. Sundberg himself has actively encouraged these contemporary adaptations, asserting that a mature behavioral science must perpetually refine its measurement precision and clinical reach.

One of the most vital modern trajectories involves the digital transformation and algorithmic automation of the VB-MAPP. The development of sophisticated electronic platforms (such as VB-MAPP App ecosystems) has revolutionized how clinicians collect, aggregate, and visualize developmental data. Researchers are currently leveraging artificial intelligence diagnostics and automated video tracking to conduct high-precision barrier assessments, analyzing micro-vocal intonations, motor imitation latencies, and gaze trajectories in infants at elevated risk for autism. Furthermore, the expansion of clinical tele-health frameworks has democratized verbal behavior interventions, allowing doctoral-level behavior analysts to guide parent-implemented NET and mand-training protocols in geographically remote and underserved global regions.

Despite these technological advances, critical scientific frontiers remain open, demanding ongoing research. The behavioral community continues to grapple with the advanced challenges Sundberg outlined decades ago: formulating scalable, empirical technologies for establishing complex, generative intraverbal dialogues; remediating subtle, advanced autoclitic deficits; systematically teaching metaphorical and abstract perspective-taking repertoires; and seamlessly conditioning conversational reciprocity between neurodivergent individuals and their social communities. The monumental foundation erected by Mark L. Sundberg from 1950 to the present provides the precise empirical, methodological, and conceptual machinery required to conquer these emergent frontiers, standing as an eternal testament to the power of radical behaviorism to illuminate and elevate the human condition.

Conclusion

The life and scholarly legacy of Mark L. Sundberg embody the triumph of operational rigor over speculative mentalism in the analysis of human communication. At a critical juncture in the history of psychology—when B. F. Skinner’s functional analysis of language was widely dismissed by mainstream cognitive science—Sundberg recognized the profound, untapped clinical potential of Verbal Behavior. Through unwavering conceptual dedication under the mentorship of Jack Michael, the courageous founding and editorship of The Analysis of Verbal Behavior, and the rigorous design of criterion-referenced diagnostic systems such as the ABLLS and the VB-MAPP, Sundberg built an enduring bridge connecting abstract behavioral philosophy to real-world humanitarian impact.

His work fundamentally altered the life trajectories of countless individuals diagnosed with autism spectrum disorders and severe developmental disabilities across the globe. By proving that human language can be parsed, taught, and cultivated through the systematic manipulation of environmental contingencies, motivating operations, and stimulus control, Sundberg dismantled the notion that non-verbal individuals are unteachable. From the precise mechanics of transitive motivating operations in early manding to the subtle operant complexities of joint control and autoclitic frames, his scholarly output constitutes a complete, empirically validated technology of language instruction. Mark Sundberg’s enduring monument is etched not merely into the pages of academic journals, but into the vibrant, spontaneous voices of hundreds of thousands of children worldwide who were taught to communicate, connect, and thrive through his science.

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