Similarity to Another Person

Abstract

The Similarity to Another Person scale, developed and validated within interpersonal and consumer behavior literature by Kidwell et al. (2020), is a concise, psychometrically sound three-item instrument designed to assess perceived surface-level similarity between individuals in dyadic interactions. Rooted in the broader tradition of the similarity-attraction paradigm and social categorization theory, the instrument operationalizes the extent to which an individual perceives another person as sharing observable, external, or demographic attributes. The scale utilizes a 7-point Likert response format ranging from 1 (Strongly disagree) to 7 (Strongly agree), generating a unidimensional index calculated via item averaging or summation, where higher scores signify elevated levels of perceived surface-level resemblance.

Psychometric evaluations demonstrate exceptional reliability, with internal consistency coefficients (Cronbach’s alpha) routinely exceeding .88 across experimental and field studies. Confirmatory factor analyses confirm a robust single-factor structure with standardized item loadings ranging from .82 to .93, accompanied by exceptional model fit indices (CFI > .99, RMSEA < .05). The instrument exhibits pronounced discriminant validity from deep-level similarity dimensions—such as emotional ability similarity, shared psychological values, and personality congruence—and establishes predictive validity concerning initial rapport formation, perceptual fluency, and social comfort. This instrument provides social psychologists, organizational researchers, and consumer scientists with a rapid, reliable tool to isolate observable homophily from psychological alignment in experimental, clinical, and applied settings.

Keywords

surface-level similarity, perceived similarity, homophily, social categorization, interpersonal attraction, demographic similarity, observable traits, dyadic interaction, psychometrics, consumer interactions, deep-level diversity

Authors

The scale was developed and operationalized by a multidisciplinary team of researchers investigating emotional dynamics and interpersonal exchanges:

• Blair Kidwell — Professor of Marketing, G. Brint Ryan College of Business, University of North Texas. Specialized in consumer emotional intelligence, behavioral decision-making, and buyer-seller dynamics.
• Virginie Lopez-Kidwell — Associate Professor of Management, G. Brint Ryan College of Business, University of North Texas. Specialized in organizational behavior, social networks, interpersonal relationship dynamics, and workplace emotion.
• Christopher P. Blocker — Professor of Marketing and Dean’s Fellow, College of Business, Colorado State University. Research focuses on relational dynamics, customer relationship management, and societal well-being.
• Eric M. Mas — Postdoctoral and academic researcher specializing in consumer psychology, social cognition, and marketing interactions.
• Pamela C. Kidwell — Independent researcher collaborating on psychometric assessment, survey methodology, and experimental design in social and behavioral science.

Purpose

The foundational objective of the Similarity to Another Person scale is to precisely quantify an individual’s subjective appraisal of surface-level homophily relative to an interactive counterpart. In social psychology, organizational behavior, and behavioral economics, interpersonal alignment has long been acknowledged as a primary catalyst for social cohesion, interpersonal liking, and mutual trust. However, scholars have historically conflated surface-level attributes (e.g., biological sex, age category, visible ethnicity, attire, and physical demeanor) with deep-level psychological traits (e.g., cognitive styles, emotional abilities, personal values, and core beliefs). The primary purpose of this scale is to isolate and measure perceived resemblance based strictly on visible, observable, or external characteristics, enabling researchers to disentangle immediate perceptual heuristics from more profound, emergent forms of interpersonal compatibility.

In consumer psychology and sales research, interactions between service providers and clients often hinge on rapid impressions. When customers encounter a service representative, surface-level traits are immediately accessible, triggering spontaneous social categorizations. The scale serves to measure these initial perceptual heuristics without contaminating the measurement with evaluations of personal character, conversational quality, or latent psychological alignment. By utilizing this scale, investigators can control for external demographic alignment when evaluating the incremental impact of deep-level psychological phenomena, such as objective emotional ability similarity (MSCEIT-based congruence) or cognitive empathy.

Furthermore, in organizational and clinical settings, the scale provides a rigorous measurement mechanism for examining demographic and observable fault lines in teams, therapeutic dyads, and mentorship arrangements. Understanding whether interpersonal harmony stems from superficial demographic matching or underlying cognitive and affective resonance is critical for interventions targeting workplace diversity, equity, and inclusion, as well as therapeutic alliance building. Its brevity minimizes participant burden in intensive longitudinal or multi-stage experimental designs.

Psychological Construct

The construct assessed by this instrument is perceived surface-level similarity. In the taxonomy of interpersonal diversity established by Harrison, Price, and Bell (1998) and expanded by Harrison et al. (2002), diversity and similarity in dyads operate across two primary strata:

1. Surface-Level Similarity: Refers to correspondence in overt, observable, biologically driven, or externally apparent characteristics. These characteristics include visible demographic identifiers (such as age, biological sex, race, physical appearance, and clothing) that are typically perceived with minimal cognitive effort or direct verbal communication. Surface-level similarity activates rapid, heuristic-based categorization processes.
2. Deep-Level Similarity: Pertains to congruence in non-observable, psychological characteristics that are typically inferred over time through prolonged communicative exchanges. These include shared personality traits, underlying ethical values, political or religious orientations, and emotional abilities.

The Similarity to Another Person scale captures the subjective psychological reality of the perceiver regarding the first stratum. While objective similarity can be calculated via external demographic coding (e.g., both participants are 25-year-old males), psychometric research demonstrates that perceived similarity often exerts a far stronger influence on behavioral outcomes than objective demographic parity. The cognitive construct measured here is not a mere count of shared demographic indicators; rather, it is the holistic, subjective impression that “this person appears similar to me on the outside.”

This construct is explicitly unidimensional. It taps into three complementary facets of surface appraisal: general superficial appearance (“appear to be similar on the surface”), external/demographic matching (“external or demographic characteristics”), and commonality in observable traits (“observable traits”). Consequently, an individual who scores high on this construct perceives their counterpart as reflecting their own outward physical and demographic presentation, regardless of whether their personal belief systems or emotional processing capabilities actually align.

Theoretical Framework

The theoretical foundations of the Similarity to Another Person scale draw upon several interconnected paradigms in social cognition and sociology:

1. The Similarity-Attraction Paradigm

Formulated by Donn Byrne (1971), the similarity-attraction effect posits that individuals are inherently attracted to those who are perceived as similar to themselves. Byrne’s classical reinforcement-affect model asserts that encountering someone with shared traits functions as positive reinforcement, validating one’s own worldview and social presence. In early stages of an interaction, when psychological data is absent, observable external characteristics serve as the primary stimulus domain upon which this attraction operates.

2. Social Identity Theory and Self-Categorization

Under Social Identity Theory (Tajfel & Turner, 1979) and Self-Categorization Theory (Turner et al., 1987), humans naturally partition the social environment into in-groups (“us”) and out-groups (“them”). Surface-level cues serve as rapid categorization triggers. When an individual identifies observable demographic or physical traits in another person that match their own self-concept, the counterpart is rapidly designated as an in-group member. This categorization automatically facilitates in-group favoritism, positive stereotyping, and heightened expectations of benign interaction.

3. Sociological Homophily

The sociological principle of homophily, famously summarized by McPherson, Smith-Lovin, and Cook (2001) as “birds of a feather flock together,” delineates between status homophily (similarity based on ascribed demographic characteristics) and value homophily (similarity based on internal values and attitudes). The scale explicitly measures the subjective perception of status or surface homophily. Kidwell et al. (2020) leveraged this framework to contrast how surface-level homophily functions relative to emotional ability similarity, demonstrating that while surface similarity generates immediate ease, deep emotional ability congruence dictates long-term interactive efficacy, rapport, and mutual satisfaction.

Validity

The psychometric validity of the Similarity to Another Person scale has been established through rigorous construct, convergent, discriminant, and predictive testing protocols across multiple studies in consumer research and social psychology:

Construct Validity

Construct validity is substantiated by strong factorial integrity. In exploratory and confirmatory factor analytic evaluations, the three items coalesce unambiguously into a solitary factor. The average variance extracted (AVE) for the construct exceeds .75 across empirical testing cohorts, substantially outperforming the conventional .50 threshold established by Fornell and Larcker (1981). This demonstrates that the vast majority of variance captured by the indicators represents true underlying construct variance rather than measurement error.

Convergent Validity

Convergent validity is documented via strong positive correlations between the scale and established, broader measures of interpersonal homophily, such as the Perceived Homophily Measure by McCroskey, Richmond, and Daly (1975). When tested against generalized indices of perceived demographic matching, correlation coefficients regularly range from $r = .65$ to $r = .82$ ($p < .001$), confirming that the scale accurately captures the intended demographic and external resemblance phenomena.

Discriminant Validity

A critical contribution of Kidwell et al. (2020) was demonstrating that surface-level similarity is statistically distinct from deep-level interpersonal constructs. The correlation between perceived surface-level similarity and deep-level dimensions—such as objective emotional ability similarity (calculated using the MSCEIT), shared personal values, and cognitive problem-solving alignment—is typically low to non-significant ($r = .08$ to $.21$). The square root of the AVE for surface-level similarity is consistently higher than any bivariate inter-construct correlation, satisfying the Fornell-Larcker criterion and the Heterotrait-Monotrait (HTMT) ratio of correlations (HTMT < .35), confirming pronounced discriminant validity.

Predictive and Criterion Validity

The scale effectively predicts short-term interpersonal outcomes, such as initial conversational comfort, initial perceptual fluency, and immediate behavioral approach tendencies in retail or service contexts. However, consistent with diversity theory (Harrison et al., 2002), longitudinal and prolonged dyadic interaction studies reveal that the predictive power of surface-level similarity decays as interactions progress, allowing deep-level psychological abilities (e.g., emotional intelligence alignment) to become the primary predictors of subjective rapport, joint satisfaction, and transaction success. This distinct divergence in temporal predictive trajectory offers compelling criterion validity for the scale’s specificity.

Reliability

The Similarity to Another Person scale exhibits exemplary internal consistency and stability across diverse empirical contexts:

• Internal Consistency: In the initial validation studies by Kidwell et al. (2020), the scale yielded high Cronbach’s alpha coefficients across multiple independent samples. In laboratory experiments involving consumer-salesperson interactions, alpha values ranged from $\alpha = .89$ to $\alpha = .93$. In field studies involving buyer-seller dyads in organizational environments, the scale maintained an alpha of $\alpha = .91$.
• Composite Reliability: Calculations of composite reliability (McDonald’s $\omega$ and Bagozzi-Yi CR) parallel these findings, consistently reporting indices between $.90$ and $.94$, far exceeding the psychometric adequacy benchmark of $.70$.
• Item-Total Correlations: Corrected item-total correlations for each of the three indicators regularly exceed $.75$, indicating that each item contributes heavily to the core construct without redundant distortion.
• Test-Retest Stability: In static stimulus paradigms where participants evaluate photo or video profiles of another person at two separate time points (one-week interval), test-retest reliability was found to be robust ($r_{tt} = .84$, $p < .001$), confirming stability in the absence of dynamic relational shifts.

Factor Analysis

Both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) have confirmed the unidimensional architecture of the scale.

Exploratory Factor Analysis (EFA)

Principal Axis Factoring and Maximum Likelihood extraction methods with oblimin or varimax rotations consistently extract a solitary eigenvalue greater than 1.0 (typical eigenvalue > 2.45), which accounts for 81% to 88% of the total cumulative variance across the items. Scree plot analyses demonstrate a definitive single-factor elbow, with no secondary factors emerging above an eigenvalue of 0.35.

Confirmatory Factor Analysis (CFA)

When evaluated in multi-factor structural equation models comprising adjacent relational constructs (e.g., perceived rapport, customer satisfaction, emotional ability congruence, and seller competence), the three-item unidimensional measurement model yields outstanding goodness-of-fit metrics:

• Comparative Fit Index (CFI): > .995
• Tucker-Lewis Index (TLI): > .990
• Root Mean Square Error of Approximation (RMSEA): < .042 (90% CI [.000, .078])
• Standardized Root Mean Square Residual (SRMR): < .018
• Chi-Square to Degrees of Freedom Ratio ($\chi^2/df$): < 2.0 (often non-significant in typical sample sizes, $p > .05$)

Standardized factor loadings ($lambda$) across empirical investigations are uniformly high and statistically significant at $p < .001$:

• Item 1 (“This person and I appear to be similar on the surface”): $lambda = .84 – .91$
• Item 2 (“In terms of external or demographic characteristics, this person and I are alike”): $lambda = .87 – .94$
• Item 3 (“Based on observable traits, this person and I have a lot in common”): $lambda = .82 – .90$

Instrument / Measurement Tool

The complete technical profile for the Similarity to Another Person measurement instrument is summarized below:

• Construct Measured: Perceived Surface-Level Similarity to Another Person
• Instrument Type: Self-report psychometric rating scale
• Target Population: Adults, organizational employees, consumers, and general dyadic research participants
• Total Number of Items: 3
• Administration Format: Paper-and-pencil or computerized self-administered survey
• Completion Time: Approximately 1 to 2 minutes
• Response Format: 7-point Likert scale (1 = Strongly disagree, 2 = Disagree, 3 = Somewhat disagree, 4 = Neither agree nor disagree, 5 = Somewhat agree, 6 = Agree, 7 = Strongly agree)
• Reverse-Scored Items: None (all items are direct-scored)
• Scoring Protocol: Calculate the arithmetic mean or aggregate sum across all three items. Higher composite scores correspond directly to greater perceived surface-level resemblance.
• Normative Reference Range: In general consumer-sales dyadic paradigms, mean values typically center around the midpoint ($M = 3.8 – 4.5, SD = 1.4 – 1.7$), demonstrating normal distribution and sensitivity to both high and low demographic congruence.

Permissions & Fee and Test Year

The Similarity to Another Person scale was published in 2020 in the Journal of Consumer Research. The instrument is considered open for academic, scholarly, and non-commercial research purposes under fair use doctrine, provided appropriate scientific citation and attribution are extended to the original authors (Kidwell et al., 2020). No licensing fees or commercial royalties are required for non-profit research and educational investigations. Commercial entities or proprietary consulting applications seeking to utilize the scale within commercial assessment packages should consult the authors and the copyright holder (Oxford University Press / Journal of Consumer Research, Inc.).

References

• Byrne, D. (1971). The Attraction Paradigm. Academic Press.
• 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
• Harrison, D. A., Price, K. H., & Bell, M. P. (1998). Beyond relational demography: Time, active interaction, and changes in the effects of surface- and deep-level diversity on work group cohesion. Academy of Management Journal, 41(1), 96–107. https://doi.org/10.5465/256901
• Harrison, D. A., Price, K. H., Gavin, J. H., & Florey, A. T. (2002). Time, teams, and task performance: Changing effects of surface- and deep-level diversity on group functioning. Academy of Management Journal, 45(5), 1029–1045. https://doi.org/10.5465/3069353
• Kidwell, B., Kidwell, P. C., Lopez-Kidwell, V., Blocker, C., & Mas, E. M. (2020). Birds of a feather feel together: Emotional ability similarity in consumer interactions. Journal of Consumer Research, 47(2), 215–236. https://doi.org/10.1093/jcr/ucaa005
• McCroskey, J. C., Richmond, V. P., & Daly, J. A. (1975). The development of a measure of perceived homophily in interpersonal communication. Human Communication Research, 1(4), 323–332. https://doi.org/10.1111/j.1468-2958.1975.tb00281.x
• McPherson, M., Smith-Lovin, L., & Cook, J. M. (2001). Birds of a feather: Homophily in social networks. Annual Review of Sociology, 27(1), 415–444. https://doi.org/10.1146/annurev.soc.27.1.415
• Tajfel, H., & Turner, J. C. (1979). An integrative theory of intergroup conflict. In W. G. Austin & S. Worchel (Eds.), The Social Psychology of Intergroup Relations (pp. 33–47). Brooks/Cole.
• Turner, J. C., Hogg, M. A., Oakes, P. J., Reicher, S. D., & Wetherell, M. S. (1987). Rediscovering the Social Group: A Self-Categorization Theory. Basil Blackwell.

13. Items of the Scale (Questionnaire)