Nine Hole Peg Test

1. Abstract

The Nine Hole Peg Test (NHPT) is an internationally recognized, standardized, quantitative assessment designed to measure finger dexterity, fine manual motor speed, and unilateral upper extremity function. Originally developed by Marianne Kellor, June Frost, Norman Silberberg, Iver Iversen, and Ray Cummings in 1971 at the Sister Kenny Institute, and subsequently standardized with extensive normative data by Virgil Mathiowetz and colleagues in 1985, the instrument serves as a cornerstone across physical therapy, occupational therapy, neurology, and clinical neurorehabilitation. The operational protocol requires the examinee to pick up nine cylindrical pegs one at a time from a container, insert them as rapidly as possible into nine corresponding holes arranged in a 3×3 matrix on a standardized board, and subsequently remove them one by one, returning them to the container. Performance is quantified strictly by the total elapsed time in seconds, administered independently for the dominant and non-dominant upper extremities. The NHPT demonstrates outstanding psychometric properties, consistently exhibiting high inter-rater reliability (intraclass correlation coefficient [ICC] ≥ .96 to .99) and robust test-retest reliability (ICC = .80 to .95 across healthy, stroke, and multiple sclerosis cohorts). Construct and convergent validity are firmly established through strong correlations with other validated upper-limb instruments, including the Box and Block Test, the Purdue Pegboard Test, and the Action Research Arm Test (ARAT). Its inclusion as the upper-extremity motor performance metric within the Multiple Sclerosis Functional Composite (MSFC) has solidified its global status as a clinical benchmark. This paper presents an exhaustive academic evaluation of the NHPT, exploring its psychometric architecture, neurocomputational constructs, factor structure, normative metrics, and evidence-based clinical utility.

2. Keywords

Nine Hole Peg Test, fine manual dexterity, finger coordination, upper extremity motor function, psychometrics, neurorehabilitation, multiple sclerosis, stroke rehabilitation, motor control, Fitts’s law, test-retest reliability, convergent validity

3. Authors

The Nine Hole Peg Test was originally formulated and introduced in 1971 by an interdisciplinary clinical research team at the Sister Kenny Institute (now the Courage Kenny Rehabilitation Institute, part of Allina Health) in Minneapolis, Minnesota, United States:

• Marianne Kellor, OTR — Occupational Therapist, Sister Kenny Institute, Minneapolis, MN.
• June Frost, OTR — Occupational Therapist, Sister Kenny Institute, Minneapolis, MN.
• Norman E. Silberberg, PhD — Clinical Psychologist and Director of Research, Sister Kenny Institute, Minneapolis, MN.
• Iver A. Iversen, MS — Biostatistician and Research Associate, Sister Kenny Institute, Minneapolis, MN.
• Ray Cummings, MD — Physiatrist and Clinical Investigator, Sister Kenny Institute, Minneapolis, MN.

Subsequent definitive standardization, psychometric refinement, and publication of comprehensive adult normative data (spanning ages 20 to 94 years) were conducted by Virgil Mathiowetz, PhD, OTR/L, FAOTA, along with Karen Volland, Nancy Kashman, and Cheryl Weber in 1985 at the University of Wisconsin-Milwaukee and the University of Minnesota.

4. Purpose

The primary purpose of the Nine Hole Peg Test is to provide a brief, objective, standardized, and highly reproducible measure of unilateral fine manual dexterity and finger motor speed. In neurorehabilitation, geriatrics, and orthopedic medicine, hand function represents a critical determinant of human autonomy, reflecting the intactness of sensory-motor integration, corticospinal pathways, and fine neuromuscular recruitment. The NHPT was designed to address the need for an inexpensive, portable, and rapid assessment tool capable of detecting subtle motor impairments that broad functional independence assessments frequently overlook.

Clinically, the NHPT is deployed to evaluate upper limb impairment, track disease progression, quantify spontaneous neurobiological recovery, and assess therapeutic efficacy following pharmacological, surgical, or physical therapy interventions. It is most prominently utilized within the following clinical populations:

• Multiple Sclerosis (MS): Selected by the National Multiple Sclerosis Society’s Clinical Assessment Task Force as the definitive upper-extremity component of the Multiple Sclerosis Functional Composite (MSFC). It detects subclinical demyelinating progression and upper limb ataxia with exceptional sensitivity.
• Cerebrovascular Accident (Stroke): Employed in acute, subacute, and chronic stroke rehabilitation to monitor hemiparetic hand recovery, motor learning, and dexterity reconstruction following interventions such as Constraint-Induced Movement Therapy (CIMT).
• Parkinson’s Disease (PD): Quantifies motor slowing (bradykinesia), fine tremor interference, and impaired sequential finger coordination during manipulative tasks.
• Peripheral Neuropathies and Upper Extremity Trauma: Evaluates functional recovery following carpal tunnel release, peripheral nerve regeneration (e.g., median or ulnar nerve repair), cervical myelopathy, and distal upper extremity fractures.
• Geriatric Functional Decline: Identifies age-related declines in hand coordination, tactile acuity, and manipulative processing speed that correlate with diminished performance in activities of daily living (ADLs) such as buttoning, eating, writing, and medication management.

From a research perspective, the NHPT serves as a continuous outcome metric in phase II and III pharmaceutical clinical trials, neurostimulation investigations (e.g., repetitive Transcranial Magnetic Stimulation [rTMS], transcranial direct current stimulation [tDCS]), and robotic rehabilitation studies. Its continuous ratio scale (seconds required to complete the task) allows for parametric statistical analyses, yielding robust effect size estimations and statistical power without ceiling effects commonly observed in ordinal functional rating scales.

5. Psychological Construct

The Nine Hole Peg Test operationalizes the psychological and neuropsychological construct of fine manual dexterity, defined as the ability to coordinate rapid, precise, goal-directed finger and hand movements to grasp, manipulate, transport, and position small physical objects. Unlike gross manual dexterity, which engages proximal musculature (shoulder and elbow) to move large objects through space, fine manual dexterity is fundamentally anchored in distal neuromuscular control, involving the intrinsic and extrinsic muscles of the hand, the thumb, and the radial digits (index and middle fingers).

Although the NHPT yields a single aggregate metric (total completion time), psychomotor and kinematic decomposition reveals that the test evaluates several interdependent psychological, sensorimotor, and biomechanical dimensions:

1. Precision Pinch and Digital Manipulation

The initial phase of each trial necessitates the execution of a pincer grasp or three-jaw chuck grasp to isolate a single 9 mm diameter peg from a concave well containing nine identical items. This requires selective digital fractionation — the capacity to move individual fingers independently of one another — alongside rapid pre-shaping of the hand based on continuous visual and somatosensory inputs.

2. Visuomotor Coordination and Spatial Aiming

Transporting each peg toward a 10 mm diameter hole and inserting it requires real-time visuomotor integration. The visual system must calculate the spatial target coordinates (allocentric space), while the motor system computes an egocentric trajectory to align the peg’s longitudinal axis perfectly parallel with the receiver hole. This process exemplifies rapid spatial aiming governed by sensory feedback correction loops.

3. Somatosensory and Tactile Proprioception

Executing the peg insertion and subsequent extraction without visual anchoring exclusively at the fingerpad requires intact tactile mechanoreceptor transduction (Meissner’s corpuscles and Merkel disks) and proprioceptive joint sense. Examinees with impaired tactile feedback exhibit prolonged positioning phases, excessive grip forces, or frequent dropping of the pegs due to defective grip-load force scaling.

4. Sequential Processing and Motor Inhibition

Cognitively, the NHPT demands cognitive endurance, sustained attention, and adherence to strict operational constraints (i.e., taking only one peg at a time, picking from the well without pre-staging, and sequencing the insertion and removal phases without pauses). Inhibitory control is necessary to resist grasping multiple pegs simultaneously when under time pressure.

5. Bilateral Motor Asymmetry

By measuring the dominant and non-dominant hands independently, the NHPT provides a sensitive psychometric metric of cerebral lateralization and bilateral motor asymmetry. Disproportionate divergence between the dominant and non-dominant completion times (typically exceeding a 10–15% physiological differential in neurotypical individuals) serves as a sensitive marker of unilateral corticospinal or basal ganglia pathology.

6. Theoretical Framework

The conceptual foundations of the Nine Hole Peg Test are rooted in motor control theory, information processing psychology, and computational neuroscience. Three primary paradigms underpin its construct and design:

1. Fitts’s Law and the Speed-Accuracy Trade-off

The core biomechanical architecture of the NHPT is an operational instantiation of Fitts’s Law (Fitts, 1954). Fitts’s Law establishes a formal mathematical relationship governing human rapid targeted movement, dictating that the movement time ($MT$) required to rapidly reach a target is a logarithmic function of the distance to the target ($D$) and the width of the target ($W$):

MT = a + b · log₂(2D / W)

Where the logarithmic term log₂(2D / W) represents the Index of Difficulty (ID) measured in bits of information. In the NHPT, the target diameter (hole width $\approx$ 10 mm) is minimally larger than the peg diameter (9 mm), creating an exceptionally high Index of Difficulty during the final insertion phase. Consequently, small degradations in motor signal-to-noise ratio within the nervous system result in exponential increases in movement time or frequent positional misses, magnifying subtle clinical deficits.

2. Closed-Loop and Open-Loop Motor Control Models

Motor execution within the NHPT alternates continuously between open-loop feedforward mechanisms and closed-loop feedback processes:

• Feedforward (Open-Loop) Ballistic Movement: During the transport phase from the container to the vicinity of the pegboard, the central nervous system (CNS) relies predominantly on pre-programmed internal models generated within the premotor cortex and cerebellum.
• Feedback (Closed-Loop) Fine Adjustment: During the terminal docking phase (aligning and inserting the peg) and the initial extraction grasp, the motor execution relies heavily on real-time visual and somatosensory closed-loop feedback routed through the posterior parietal cortex and primary motor cortex (M1) to correct minute trajectory errors.

3. Corticospinal Tract Fractionation and Neuroanatomy

Phylogenetically and neuroanatomically, independent finger movements (fractionation) are mediated uniquely by direct corticomotoneuronal connections — monosynaptic projections extending directly from the primary motor cortex (Brodmann area 4) onto alpha motor neurons located in the anterior horn of the cervical spinal cord. In humans and higher non-human primates, these direct monosynaptic pathways bypass spinal interneurons, enabling high-speed, isolated digital dexterity. Lesions affecting the corticospinal pathway (e.g., middle cerebral artery ischemic stroke, focal demyelinating plaques in MS) disrupt this monosynaptic substrate, forcing the CNS to rely on phylogenetically older, polysynaptic pathways (e.g., the reticulospinal tract), which enforce stereotypical, multi-finger flexor synergies and destroy the fine dexterity evaluated by the NHPT.

7. Validity

The Nine Hole Peg Test has undergone extensive psychometric validation across healthy developmental populations and diverse pathological groups, confirming its construct, convergent, discriminant, and predictive validity.

1. Convergent Validity

Convergent validity has been established through comparative analyses with concurrent upper limb performance assessments. In their landmark study, Mathiowetz et al. (1985) reported strong, statistically significant correlations between the NHPT and the Purdue Pegboard Test ($r = -.61$ to $-.69$, where negative correlations reflect inverse operational scaling, as Purdue counts pegs placed in a fixed time while NHPT measures total elapsed time). Further studies in stroke cohorts have demonstrated high correlations with the Box and Block Test ($r = -.80$ to $-.88$) and the Action Research Arm Test ($r = -.75$ to $-.85$). In multiple sclerosis cohorts, NHPT scores correlate strongly with the Arm, Shoulder and Hand (DASH) questionnaire and objective sensory testing parameters ($r = .65$ to $.78$).

2. Discriminant and Known-Groups Validity

The NHPT exhibits outstanding discriminant validity, reliably differentiating between healthy individuals and clinical populations, as well as stratifying severity stages within chronic neurological disorders. Mathiowetz et al. (1985) showed significant differences across age brackets, with completion times increasing steadily after the sixth decade of life. In Multiple Sclerosis studies (Cutter et al., 1999; Fischer et al., 1999), the NHPT demonstrated clear differentiation between patients with varying Expanded Disability Status Scale (EDSS) scores, discriminating between relapsing-remitting and secondary progressive phenotypes based on manual dexterity decline.

3. Predictive Validity and Ecological Relevance

NHPT completion times correlate significantly with subjective independence in instrumental activities of daily living (IADLs), fine motor self-efficacy, and vocational viability. In chronic post-stroke populations, baseline NHPT performance predicts long-term functional recovery at 6 and 12 months post-insult, explaining substantial variance in functional independence measures (FIM) and hand-specific domains of the Stroke Impact Scale (SIS).

4. Sensitivity to Change (Responsiveness)

The continuous time metric renders the NHPT highly sensitive to subtle neurorehabilitative improvements and subclinical disease exacerbations. In clinical trials of Multiple Sclerosis (e.g., natalizumab, ocrelizumab), a 20% change in NHPT completion time (or 20% change in pegs-per-second transformation) is widely accepted as a clinically meaningful benchmark representing true clinical improvement or progression, showing higher responsiveness than broad ordinal neurological scales.

8. Reliability

The psychometric literature confirms the Nine Hole Peg Test as one of the most reliable performance-based functional motor measures available in clinical medicine.

1. Inter-Rater Reliability

Because the NHPT protocol utilizes objective mechanical timing (stopwatch) tied to standardized physical events (first peg touch through last peg container placement), observer variability is minimal. Mathiowetz et al. (1985) demonstrated virtually perfect inter-rater reliability among healthy adult populations, reporting Pearson correlation coefficients of $r = .97$ for the dominant hand and $r = .99$ for the non-dominant hand. Subsequent investigations utilizing Intraclass Correlation Coefficients (ICC) have replicated these metrics, documenting inter-rater ICCs ranging between .96 and .99 across various neurological rehabilitation settings.

2. Test-Retest Reliability

Test-retest stability has been evaluated extensively across varying testing intervals:

• Healthy Adults: Mathiowetz et al. (1985) reported moderate-to-high test-retest coefficients ($r = .69$ for the right hand, $r = .43$ for the left hand) in healthy individuals using a single-trial test-retest protocol over a one-week interval, noting that practice effects slightly suppressed correlation values. When using the average of two trials, test-retest ICCs routinely exceed .80 to .90.
• Multiple Sclerosis: In MS cohorts evaluated within the MSFC framework, test-retest reliability is exceptionally high, with ICCs consistently documented between .85 and .95 across independent assessment days.
• Stroke Patients: Chen et al. (2009) established test-retest reliability ICC values of .95 (dominant) and .93 (non-dominant) in subacute and chronic stroke cohorts, demonstrating substantial measurement stability.

3. Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC)

Empirical calculations provide concrete parameters for determining whether changes in patient performance exceed inherent measurement noise:

• Standard Error of Measurement (SEM): In stroke patients, the SEM for total completion time is approximately 1.5 to 2.6 seconds.
• Minimal Detectable Change at 95% Confidence (MDC₉₅): Studies establish an MDC₉₅ of approximately 4.2 to 7.3 seconds in hemiparetic stroke cohorts. Expressed as a percentage, a change exceeding 20% in raw completion time provides 95% statistical confidence of true functional alteration beyond random variability and familiarization effects.

9. Factor Analysis

Although the Nine Hole Peg Test yields a single composite score (completion time in seconds), its structural placement within multi-test functional batteries has been extensively scrutinized using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA).

1. Structural Battery Loadings

In broad upper-extremity psychomotor batteries evaluating stroke and geriatric cohorts (combining instruments like the Box and Block Test, Grip Dynamometry, Pinch Dynamometry, and the Jebsen-Taylor Hand Function Test), factor analytic models typically extract two distinct latent factors:

• Factor 1: Gross Upper Limb Motor Capacity & Force — Defined by isometric grip strength, lateral pinch strength, and proximal reaching speed.
• Factor 2: Distal Fine Manual Dexterity & Coordination — Defined by high factor loadings on the Nine Hole Peg Test (λ = .82 to .89) and the Purdue Pegboard Test (λ = .78 to .85).

These findings demonstrate that the NHPT possesses robust structural integrity as a distinct, unidimensional measure of distal finger dexterity that does not collapse into broad isometric force or gross reaching constructs.

2. Kinematic Task Decomposition (Sub-Movement Factors)

Modern biomechanical and motion-capture investigations (e.g., using 3D optoelectronic tracking and instrumented pegboards) have deconstructed the operational steps of the NHPT into latent kinematic sub-components:

• Reach-to-Grasp Component (Pre-Shaping & Isolation): Time taken to move the hand to the well and isolate a single peg.
• Transport Component (Gross Aiming): High-velocity spatial displacement from container to pegboard matrix.
• Insertion Component (High-Precision Docking): Terminal alignment and downward insertion into the hole (accounting for ~45% of total variance in neurologically impaired subjects).
• Removal Component (Grasp & Extraction): Low-precision rapid clearance of pegs back into the container.

Confirmatory models reveal that while insertion and removal both load on the overarching latent factor of manual speed, the insertion phase captures distinct variance associated with sensory-guided visual feedback, tremor amplification, and fine spatial error correction.

10. Instrument / Measurement Tool

The Nine Hole Peg Test is a performance-based instrumental assessment. Below are the structural, procedural, and scoring specifications established in the standardized literature:

1. Apparatus Specifications

• Board: Standardized rectangular board (wood or molded plastic), approximately 25.0 cm × 12.7 cm × 3.8 cm (commercial variants may measure 12.0 cm × 12.0 cm square).
• Well / Container: A concave bowl or hollowed-out basin positioned on one end of the board (measuring approximately 10.0 cm in diameter and 2.5 cm in depth) containing the pegs.
• Hole Array: Nine cylindrical holes arranged in a 3 × 3 square matrix, centered 3.2 cm (1.25 inches) apart from center to center. The hole diameter is 10.0 mm (0.39 inches), with a depth of 13.0 mm (0.5 inches).
• Pegs: Nine identical smooth cylindrical pegs (wood or plastic), each measuring 9.0 mm (0.35 inches) in diameter and 32.0 mm (1.26 inches) in length.
• Stopwatch: Digital timing device measuring in seconds and tenths/hundredths of a second.

2. Standardized Administration Protocol (Mathiowetz Formulation)

• Seating & Placement: The examinee is seated comfortably at a standard-height table with the pegboard centered directly along their midsagittal plane. The container well is oriented toward the hand being evaluated (e.g., when testing the right hand, the well is placed on the right side and the holes on the left side).
• Hand Order: Testing begins with the dominant hand, followed by the non-dominant hand (or unaffected hand first in hemiparetic patients, followed by the affected limb).
• Stabilization: The non-tested hand may hold the base of the pegboard to stabilize it against the table surface.
• Execution Rules:
  • The examinee must pick up only one peg at a time.
  • Pegs can be placed into the holes in any sequence (rows, columns, or random).
  • Once all nine pegs are placed in the holes, the examinee must immediately remove them one at a time and return them to the container.
  • Pegs must not be dropped into the container from a height; they must be placed back.
  • If a peg is dropped on the floor or table, the stopwatch continues running, and the examiner either provides a spare peg or instructs the participant to retrieve it (per standardized clinic protocol).
• Practice & Trials: A single practice trial of placing and removing all 9 pegs is provided to establish task comprehension, followed immediately by one or two timed test trials per hand. In MSFC administration, two consecutive timed trials per hand are executed, with scores averaged.

3. Scoring and Derived Metrics

• Primary Metric (Time): Total elapsed time in seconds from the moment the examinee’s finger touches the first peg in the well until the final (ninth) peg is deposited back into the container.
• Pegs-per-Second Transformation (Reciprocal Score): In severely impaired cohorts unable to complete the test within a maximum cut-off ceiling (e.g., 300 seconds), a reciprocal transformation is employed to eliminate infinite scores:

  Pegs per Second = 18 / Total Time (seconds)

  If an individual places and removes only 4 pegs in 300 seconds, their operational score reflects (pegs placed + pegs removed) / 300.

• Normative Reference Standard (Mathiowetz et al., 1985): Adult reference values (mean completion times in seconds ± standard deviation) across key age cohorts:

11. Permissions & Fee and Test Year

The Nine Hole Peg Test was originally described in the public domain by Marianne Kellor and colleagues in 1971 in their publication appearing in the American Journal of Occupational Therapy. The theoretical concept, procedural guidelines, and normative data are not subject to restrictive intellectual property licensing; therefore, clinicians and academic researchers may construct, administer, and interpret the test without paying licensing fees or royalties.

Physical manufactured apparatuses meeting standardized dimensions are sold commercially by medical supply companies and rehabilitation instrument distributors (e.g., Sammons Preston, Rolyan, Jamar, and Fabrication Enterprises) at prices typically ranging from $50 to$180 USD. Standardized administration manuals, data sheets, and normative tables from Virgil Mathiowetz and colleagues (1985) are freely accessible in published academic literature for research and clinical use.

12. References

Chen, H. M., Chen, C. C., Hsueh, I. P., Huang, S. L., & Hsieh, C. L. (2009). Test-retest reproducibility and smallest real difference of 5 hand function tests in patients with stroke. Neurorehabilitation and Neural Repair, 23(5), 435–440. https://doi.org/10.1177/1545968308331146

Cutter, G. R., Baier, M. L., Rudick, R. A., Cookfair, D. L., Fischer, J. S., Petkau, J., Syndulko, K., Matthews, C. G., Antel, J. P., Francis, G. S., & Lublin, F. D. (1999). Development of a Multiple Sclerosis Functional Composite as a clinical trial outcome measure. Brain, 122(5), 871–882. https://doi.org/10.1093/brain/122.5.871

Earhart, G. M., Cavanaugh, J. T., Ellis, T., Ford, M. P., Foreman, K. B., & Dibble, L. E. (2011). The 9-hole PEG test of upper extremity function: Average values, test-retest reliability, and dual task impairment in people with Parkinson disease. Journal of Neurologic Physical Therapy, 35(4), 157–163. https://doi.org/10.1097/NPT.0b013e318235da3b

Fischer, J. S., Rudick, R. A., Cutter, G. R., & Reingold, S. C. (1999). The Multiple Sclerosis Functional Composite Measure (MSFC): An integrated approach to MS clinical outcome assessment. Neurology, 53(9), 2124–2124. https://doi.org/10.1212/WNL.53.9.2124

Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6), 381–391. https://doi.org/10.1037/h0055392

Kellor, M., Frost, J., Silberberg, N., Iversen, I., & Cummings, R. (1971). Hand strength and dexterity: Norms for clinical use. American Journal of Occupational Therapy, 25(2), 77–83.

Mathiowetz, V., Kashman, N., Volland, K., & Weber, K. (1985). Adult norms for the Nine Hole Peg Test of finger dexterity. The Occupational Therapy Journal of Research, 5(1), 24–38. https://doi.org/10.1177/153944928500500102

Mathiowetz, V., Weber, K., Kashman, N., & Volland, K. (1985). Adult norms for the Nine Hole Peg Test of finger dexterity. In: American Occupational Therapy Association Research Documentation Series.

Oxford Grice, K., Vogel, K. A., Le, V., Mitchell, A., Muniz, S., & Vollmer, M. A. (2003). Adult norms for a commercially available Nine Hole Peg Test for finger dexterity. American Journal of Occupational Therapy, 57(5), 570–573. https://doi.org/10.5014/ajot.57.5.570

Wang, Y. C., Bohannon, R. W., Kapellusch, J., Garg, A., & Gershon, R. C. (2015). Dexterity as measured with the 9-Hole Peg Test (9-HPT) across the lifespan: NIH Toolbox Normative Study. Journal of Hand Therapy, 28(1), 53–60. https://doi.org/10.1016/j.jht.2014.09.002

13. Items of the Scale