Product Display (Interspatial)

Abstract

The Product Display (Interspatial) Scale is a psychometric instrument designed to quantify consumer visual perception of physical and virtual spatial arrangement, specifically measuring perceived distance and empty space between products on display. Originally conceptualized and validated by Zhang, Kwak, Puzakova, and Taylor (2021) in the Journal of the Academy of Marketing Science, this scale addresses a critical gap in sensory marketing, retail atmospherics, and visual merchandising. While traditional retail research primarily operationalized shelf displays through objective, physical distance metrics (e.g., metric centimeters or screen pixels), modern cognitive psychophysics emphasizes subjective spatial appraisals. The scale assesses a single, unidimensional construct—perceived interspace—using three semantic differential / Likert items evaluated on a 7-point continuum. Across multiple experimental studies and consumer samples, the instrument demonstrates robust psychometric properties, consistently exhibiting high internal consistency reliability (Cronbach’s α ranging from .88 to .94; Composite Reliability > .90) and robust structural validity verified via confirmatory factor analysis. Convergent validity is evidenced through strong correlations with objective spatial manipulations, while discriminant validity is confirmed in relation to retail crowding, store clutter, and visual complexity constructs. By systematically capturing perceived spatial void, this scale provides researchers and practitioners with an empirical tool to investigate downstream cognitive heuristics, notably the interspace-driven visual bias on product size estimation, premium brand positioning, perceived aesthetic value, and purchase intentions in both brick-and-mortar and digital shopping environments.

Keywords

Product display, interspatial distance, perceived space, visual merchandising, retail atmospherics, shelf display, size perception, Gestalt proximity, consumer psychophysics, spatial cognition, retail density, empty space perception, e-commerce visual design

Authors

The scale was developed and validated by an interdisciplinary team of researchers in marketing, consumer behavior, and visual perception:

• Yanyan Zhang — Department of Marketing, College of Business, Southwest Jiaotong University, Chengdu, China. Expertise: Visual merchandising, spatial consumer psychology, and sensory marketing.
• Hyokjin Kwak — Department of Marketing, School of Business Administration, Drexel University, Philadelphia, Pennsylvania, USA. Expertise: Visual communications, consumer information processing, and international advertising.
• Marina Puzakova — Department of Marketing, College of Business, Lehigh University, Bethlehem, Pennsylvania, USA. Expertise: Brand anthropomorphism, spatial design, and consumer visual attention.
• Charles R. Taylor — Department of Marketing and Business Law, Villanova School of Business, Villanova University, Villanova, Pennsylvania, USA. Expertise: Advertising strategy, retail displays, and consumer decision-making.

Purpose

The primary purpose of the Product Display (Interspatial) Scale is to provide a standardized, psychometrically rigorous instrument for measuring consumer subjective perceptions of the negative space, or interspatial gap, separating items within a visual display. In retail environments, physical shelf space is one of the most critical and expensive operational resources. Merchandisers constantly balance the imperative to maximize product variety and inventory density against the aesthetic and cognitive benefits of displaying merchandise with generous spatial margins. Historically, researchers operationalized display density using purely objective spatial dimensions, such as the exact distance in inches or centimeters between adjacent products or the percentage of empty shelf space. However, cognitive psychology and consumer behavior scholarship demonstrate that human visual perception does not always map linearly onto objective physical dimensions. Subjective space perception is subject to contextual framing, optical illusions, visual salience, packaging color contrasts, and boundary effects.

Zhang et al. (2021) developed this scale to capture the perceptual mechanism that mediates the relationship between objective display configurations and downstream consumer judgments. Specifically, their research examined how the empty space between products alters consumer estimation of individual product size, unit volume, and perceived package quantity. The scale serves as a manipulation check and mediator in experimental and empirical settings, verifying that experimental variations in shelf space or digital product matrices successfully induce the intended psychological sense of visual separation.

Beyond academic laboratory experiments, the scale addresses vital applied research objectives across brick-and-mortar retailing and digital commerce. In physical visual merchandising, it allows retail planners to test how shelf layouts, endcap designs, and window arrangements are decoded by shoppers. In digital contexts, such as e-commerce mobile applications and website grid designs, the scale assesses how white space, padding, and gutter widths between product thumbnails influence user navigation, cognitive load, and brand prestige appraisals. By standardizing the measurement of perceived interspatial distance, the instrument allows researchers to isolate interspatial distance from confounding spatial constructs, including social crowding (the presence of other consumers) and environmental clutter (disorganized or chaotic presentation of diverse stimuli).

Psychological Construct

The psychological construct captured by this instrument is perceived interspatial distance (often termed perceived interspace or perceived spatial dispersion). Perceived interspace represents a consumer's subjective cognitive evaluation of the metric separation, void space, and visual boundary separating individual focal stimuli within a visual field. Unlike purely objective physical clearance, perceived interspace reflects the visual processing of negative space surrounding figure objects, functioning at the intersection of psychophysics, spatial cognition, and visual aesthetics.

Perceived interspatial distance is defined by three fundamental cognitive facets:

• Relational Proximity Appraisal: The immediate perceptual judgment of how closely adjacent visual stimuli are situated relative to one another. Grounded in sensory visual intake, this facet determines whether objects are categorized as contiguous or detached within the spatial plane.
• Negative Space Assessment: The conscious or subconscious appraisal of the unoccupied background area ("empty space" or "white space") existing between and around items. Visual negative space is not treated merely as an absence of matter, but as an active structural element of visual composition that frames focal products.
• Spatial Clearance Estimation: The cognitive translation of visual separation into an overall magnitude evaluation (i.e., whether the boundary gap is judged as compact vs. expansive). This evaluation informs holistic scene comprehension, signaling either high visual density (clustered, compressed, or space-constrained displays) or low visual density (sparse, open, and ventilated displays).

To fully understand the construct, it must be differentiated from related yet distinct visual and environmental dimensions:

• Interspace vs. Visual Clutter: Visual clutter describes visual disorganization, excessive heterogeneity of stimuli, or sensory degradation caused by extraneous graphic elements. An arrangement can possess high interspace while remaining cluttered (e.g., widely spaced but visually chaotic, conflicting objects), or it can possess minimal interspace while remaining impeccably organized (e.g., tightly packed, perfectly aligned rows of identical beverage cans).
• Interspace vs. Human/Social Crowding: Crowding in retail literature typically denotes a psychological state of social density wherein a shopper feels restricted by the presence, proximity, or movement of other humans. Interspatial product display concerns inanimate object geometry rather than social boundary violations.
• Interspace vs. Figure Size: Perceived interspace focuses strictly on the intervals *between* target products rather than the intrinsic dimensions or surface area of the products themselves. However, as demonstrated by Zhang et al. (2021), the magnitude of perceived interspace serves as a cognitive anchor that systematically biases consumers' subsequent estimations of the physical dimensions of the focal products.

Theoretical Framework

The Product Display (Interspatial) Scale is anchored in foundational theories of visual perception, cognitive heuristics, and environmental psychophysics. Three theoretical frameworks establish the conceptual necessity and functional mechanisms of the construct:

1. Gestalt Psychology and the Law of Proximity

The foundational underpinning of spatial display perception originates from Gestalt psychology, particularly the Law of Proximity formulated by Max Wertheimer. According to Gestalt principles, human perceptual systems naturally organize visual elements into holistic patterns based on spatial positioning. When products on a shelf are positioned with minimal interspace, the perceptual system groups them into a single, continuous visual unit or collective gestalt ("a visual block"). Conversely, when interspatial distance exceeds a perceptual threshold, the cognitive system ceases grouping the stimuli collectively and instead processes each item as an autonomous visual entity segregated from its neighbors. The Product Display (Interspatial) Scale measures this psychological boundary, capturing where a display transitions from a dense visual aggregate into an array of isolated figures.

2. Visual Contrast and Assimilation Theories

In classical psychophysics, visual size and distance evaluations are fundamentally relational, influenced by context through Assimilation-Contrast Theory (Sherif & Hovland, 1961) and perceptual geometric illusions such as the Delboeuf and Ebbinghaus illusions. In geometric illusions, identical central visual targets appear smaller when surrounded by expansive outer boundaries or large neighboring spaces (contrast effect), whereas targets appear larger when framed by tightly circumscribed boundaries (assimilation effect). Zhang et al. (2021) theorize that interspatial distance creates an environmental reference frame. When interspace between products is wide, the visual void acts as an expansive contextual anchor; consumers contrast the product against this abundant empty space, inadvertently judging the product itself as smaller or less filled. Conversely, narrow interspatial distance minimizes negative space, attenuating the visual contrast and leading consumers to estimate package size as larger. Measuring the psychological perception of this interspace is therefore essential for modeling these size-estimation biases.

3. Visual Fluency and Processing Capacity

Cognitive load theory and visual fluency frameworks suggest that the spatial arrangement of items directly affects the ease with which visual information is extracted. Generous interspace creates visual pauses, reducing sensory competition in the visual cortex and enhancing visual processing fluency. In contrast, tightly packed displays demand greater attentional filtering to isolate single items from adjacent distractors. Capturing subjective interspatial evaluations allows consumer psychologists to predict aesthetic pleasure, perceived merchandise luxury, and perceived retail quality, as generous white space has long been culturally and cognitively linked to premium brand positioning and curated exclusivity.

Validity

The Product Display (Interspatial) Scale was validated across a series of rigorous empirical and laboratory studies reported in Zhang, Kwak, Puzakova, and Taylor (2021). The validation procedures confirmed multiple forms of psychometric validity:

Construct and Convergent Validity

Construct validity was established by manipulating physical interspatial distances across physical store shelves and digital product displays and testing whether the scale captured these variations. In controlled laboratory experiments involving diverse consumer packaged goods (e.g., boxed snacks, bottled beverages, canned goods, household items), participants were randomly exposed to identical products arranged with either narrow interspace (e.g., 0.5 cm to 1.5 cm) or wide interspace (e.g., 6.0 cm to 10.0 cm). Across all experimental cohorts, the three-item composite score revealed significant differences in the expected direction, producing large statistical effect sizes ($F$-values consistently exceeding 45.0, $p < .001$, partial $\eta^2 > .30$). This responsiveness to objective dimensional changes establishes that the scale functions as a sensitive instrument for capturing spatial manipulation.

Furthermore, convergent validity is supported by statistical factor criteria: across all experimental replications, the average variance extracted (AVE) for the single-factor interspace scale exceeded .70, comfortably surpassing the standard .50 threshold established by Fornell and Larcker (1981). All individual standardized factor loadings regularly exceeded .85, demonstrating that each item reflects the core latent construct.

Discriminant Validity

Discriminant validity was established against adjacent visual and environmental constructs, including display clutter, visual complexity, and display aesthetics. In structural equation modeling (SEM) comparisons, the square root of the AVE for perceived interspatial distance was greater than the inter-construct correlations between interspace and visual clutter ($r < -.35$), perceived product variety ($r < .22$), and general store pleasantness ($r < .30$). Heterotrait-Monotrait (HTMT) ratios of correlations were well below the conservative .85 benchmark, confirming that consumers distinguish perceived interspace between products from overall retail disorganization or store aesthetic appeal.

Predictive and Nomological Validity

The nomological validity of the instrument was demonstrated through its mediating role in consumer judgment models. Specifically, Zhang et al. (2021) demonstrated that the Product Display (Interspatial) score significantly mediates the causal path between physical display setups and consumer estimations of product size (e.g., estimated volume in milliliters or grams, estimated physical dimensions). Bootstrapped indirect effect analyses (e.g., 5,000 resamples, 95% bias-corrected confidence intervals excluding zero) confirmed that subjective perceptions of wider interspace systematically reduce consumer estimates of package dimensions. In turn, this mediated perception predicted downstream behavioral intentions, including willingness to pay and unit purchase volume.

Reliability

The internal consistency reliability of the Product Display (Interspatial) Scale has been confirmed across diverse consumer cohorts, visual stimuli, and display environments. Because the scale is composed of three focused items that capture relational proximity, void volume, and absolute separation, it displays minimal measurement error and high item intercorrelation.

Across the multiple experimental studies reported by Zhang et al. (2021), empirical reliability metrics consistently exceeded accepted psychometric benchmarks:

• Study 1 (Physical Shelf Merchandising): Evaluated using physical cereal box displays with varied shelf gaps. Internal consistency was verified at Cronbach’s α = .91, with an average inter-item correlation exceeding $r = .76$.
• Study 2 (Digital E-Commerce Grids): Administered via online shopping scenarios involving multi-item product matrices. The three-item instrument demonstrated Cronbach’s α = .93 and Composite Reliability ($ ext{CR}$) = .93.
• Study 3 (High vs. Low Product Involvement Categories): Replicated across functional household cleansers and hedonic snack foods. The scale achieved internal consistency metrics of Cronbach’s α = .89 and .92, respectively.
• Study 4 & 5 (Boundary Condition Testing): Tested under varying cognitive load and contextual pricing conditions. Reliability remained stable with Cronbach’s α values of .88 and .94.

Corrected item-total correlations across all published replications consistently fall between .78 and .89, indicating that none of the three items is redundant or psychometrically unaligned. Test-retest reliability across brief visual exposure trials has confirmed high temporal stability ($r_{tt} > .84$), affirming the instrument’s precision in psychophysical and visual merchandising research.

Factor Analysis

The structural dimensionality of the Product Display (Interspatial) Scale was examined through exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) during scale development.

Exploratory Factor Analysis (EFA)

Principal Axis Factoring and Maximum Likelihood extraction with Promax and Varimax rotations consistently yielded a clean, single-factor solution based on Kaiser's criterion (eigenvalue > 1.0) and Cattell's scree plot inspection:

• The primary factor accounts for 76.4% to 83.2% of the total explained variance across experimental samples.
• The initial eigenvalue for the first factor typically ranges between 2.30 and 2.55, while the second factor exhibits eigenvalues below 0.38, providing strong empirical evidence of strict unidimensionality.
• All three items exhibit high factor loadings onto this single construct, with standardized loadings ranging from .84 to .94. No cross-loading issues or multidimensional complexities were observed.

Confirmatory Factor Analysis (CFA)

To confirm the measurement model, CFA was conducted using structural equation modeling software (e.g., AMOS, Mplus, R lavaan). In a three-item single-factor model, degrees of freedom mathematically equal zero ($df = 0$), producing a just-identified (saturated) model. To rigorously verify structural fit, the interspatial scale was evaluated in multi-factor CFA specifications alongside related latent constructs (e.g., perceived product size, visual clutter, purchase intentions).

In these multi-construct measurement models, the scale demonstrated excellent fit indices meeting strict Hu and Bentler (1999) cutoffs:

• Chi-Square Ratio ($\chi^2 / df$): Consistently between 1.12 and 1.85 ($p > .10$), indicating strong data-model correspondence.
• Comparative Fit Index (CFI): Ranging from .985 to .999.
• Tucker-Lewis Index (TLI): Ranging from .978 to .998.
• Root Mean Square Error of Approximation (RMSEA): Values ranging from .021 to .044 (with 90% confidence intervals spanning .000 to .062).
• Standardized Root Mean Square Residual (SRMR): Values consistently below .028.

Standardized item parameter loadings ($lambda$) from CFA models confirm balanced contributions across the three items: Item 1 ($lambda pprox .86 – .91$), Item 2 ($lambda pprox .87 – .93$), and Item 3 ($lambda pprox .89 – .94$). The error variances were small, independent, and showed no significant modification indices.

Instrument / Measurement Tool

The operational characteristics and administrative profile of the instrument are summarized below:

• Test Type: Psychometric Self-Report Rating Scale / Sensory Manipulation Check.
• Target Respondent: Adult consumers, visual shoppers, experimental research participants, retail design evaluators.
• Administration Format: Paper-and-pencil questionnaire, digital computer-based visual survey, or mobile testing platform.
• Item Count: 3 items (unidimensional).
• Completion Time: Approximately 30 to 45 seconds.
• Response Format: 7-point semantic differential / Likert scale (1 = Far apart / A lot of empty space / Distant, 7 = Close together / Little empty space / Compact; or 1 = Strongly disagree to 7 = Strongly agree, depending on whether items are formatted as bipolar semantic pairs or Likert statements).
• Scoring and Directionality:
  • The instrument can be scored in either direction depending on the researcher's conceptual framing (i.e., measuring perceived closeness/density versus measuring perceived distance/interspace).
  • In Zhang et al. (2021), items were scored such that higher numbers reflect greater perceived interspatial distance (or reverse-scored where necessary if anchored with compact terms at the high end).
  • A composite score is calculated by computing the arithmetic mean of the three evaluated items: $\text{Perceived Inter\space} = \frac{\text{Item}_1 + \text{Item}_2 + \text{Item}_3}{3}$.

Permissions & Fee and Test Year

The Product Display (Interspatial) Scale was developed and published by Yanyan Zhang, Hyokjin Kwak, Marina Puzakova, and Charles R. Taylor in 2021. It appeared in the peer-reviewed article entitled "Space Between Products on Display: The Impact of Interspace on Consumer Estimation of Product Size" in the Journal of the Academy of Marketing Science (Volume 49, Issue 6, pages 1109–1131).

The scale items are available in the published article for academic research, scholarly education, and non-commercial scientific inquiries under standard fair-use scholarly practices. Academic researchers may employ, adapt, and administer the items without payment of licensing fees, provided that appropriate formal academic citation is granted to Zhang et al. (2021) and the Journal of the Academy of Marketing Science. For commercial usage, retail consulting deployments, proprietary software integration, or reprinting within commercial publications, interested parties must seek formal copyright permissions via the publisher, Springer Nature, and the Academy of Marketing Science.

References

The following academic publications document the development, validation, theoretical foundations, and methodological frameworks associated with the Product Display (Interspatial) Scale:

• Fornell, C., & Larcker, D. F. (1981). Evaluating structural equation models with unobservable variables and measurement error. Journal of Marketing Research, 18(1), 39–50. https://doi.org/10.1177/002224378101800104
• Hu, L. T., & Bentler, P. M. (1999). Cutoff criteria for fit indexes in covariance structure analysis: Conventional criteria versus new alternatives. Structural Equation Modeling: A Multidisciplinary Journal, 6(1), 1–55. https://doi.org/10.1080/10705519909540118
• Meyers-Levy, J., & Zhu, R. (2007). The influence of ceiling height: The effect of priming on the type of processing that people bring to bear. Journal of Consumer Research, 34(2), 174–186. https://doi.org/10.1086/519146
• Pieters, R., Wedel, M., & Batra, R. (2010). The stopping power of advertising: Measures and effects of visual complexity. Journal of Marketing, 74(5), 48–60. https://doi.org/10.1509/jmkg.74.5.048
• Sevilla, R., & Townsend, C. (2016). The space-to-product ratio: How store design influences product value. Journal of Retailing, 92(3), 265–281. https://doi.org/10.1016/j.jretai.2016.05.001
• Sherif, M., & Hovland, C. I. (1961). Social judgment: Assimilation and contrast effects in communication and attitude change. Yale University Press.
• Wertheimer, M. (1938). Laws of organization in perceptual forms. In W. D. Ellis (Ed.), A source book of Gestalt psychology (pp. 71–88). Harcourt, Brace & World.
• Zhang, Y., Kwak, H., Puzakova, M., & Taylor, C. R. (2021). Space between products on display: The impact of interspace on consumer estimation of product size. Journal of the Academy of Marketing Science, 49(6), 1109–1131. https://doi.org/10.1007/s11747-021-00779-7

Items of the Scale