Perceived Interpersonal Similarity (PIS)

Abstract

The Perceived Interpersonal Similarity (PIS) scale is a brief psychometric instrument designed to assess an individual’s subjective appraisal of likeness, congruence, and shared characteristics between themselves and a focal target person. Adapted and operationalized extensively within social cognition, communication studies, and consumer psychology—most notably by Grant Packard, Andrew D. Gershoff, and David B. Wooten (2016)—the instrument captures the degree to which an observer perceives another social actor to be similar to themselves across core personal, experiential, and dispositional dimensions. Structured as a three-item semantic differential or bipolar Likert-type scale, the PIS prompts respondents to rate perceived concordance on endpoints typically anchored from "not at all" to "very much" (or semantic equivalents such as "very dissimilar / very similar" and "nothing like me / very much like me"). Psychometrically, the instrument exhibits strong unidimensionality, marked by high internal consistency reliability (frequently yielding Cronbach’s alpha values exceeding α = .85 and composite reliability values ω > .88) and robust construct, convergent, and discriminant validity across varied experimental manipulations and field surveys. In empirical investigations, the scale serves as a critical manipulation check, mediating variable, or explanatory mechanism through which interpersonal communication, word-of-mouth (WOM) transmission, source credibility, and persuasive appeals exert their behavioral effects. By capturing rapid, heuristic, and deliberative evaluations of psychological proximity, the PIS bridges foundational social-psychological paradigms—such as Byrne’s similarity-attraction effect, Festinger’s social comparison theory, and Turner’s self-categorization framework—with contemporary models of social influence, interpersonal perception, and consumer decision-making.

Keywords

Perceived Interpersonal Similarity, homophily, social comparison theory, similarity-attraction effect, word-of-mouth (WOM), source credibility, interpersonal perception, psychometrics, semantic differential scale, social influence, consumer psychology, manipulation check.

Authors

The three-item formulation of the Perceived Interpersonal Similarity (PIS) measure analyzed herein was operationalized and validated in consumer research by a distinguished team of behavioral scholars:

• Grant Packard, Ph.D. — Associate Professor of Marketing at the Schulich School of Business, York University, Toronto, Canada. Dr. Packard’s research focuses on language, interpersonal communication, consumer psychology, and social dynamics in word-of-mouth and customer-firm interactions.
• Andrew D. Gershoff, Ph.D. — Professor of Marketing and Gene Edwards Professor in Banking at the McCombs School of Business, The University of Texas at Austin, Austin, Texas, USA. His scholarship investigates consumer judgment, decision-making, interpersonal evaluation, and trust.
• David B. Wooten, Ph.D. — Professor of Marketing and Alfred L. Edwards Collegiate Professor at the Stephen M. Ross School of Business, University of Michigan, Ann Arbor, Michigan, USA. Dr. Wooten specializes in social influence, consumer self-presentation, word-of-mouth transmission, and consumption symbolism.

Direct inquiries regarding the foundational empirical context of this operationalization can be directed to the corresponding authors via their respective academic institutions or through the publication records indexed in the Journal of Consumer Research.

Purpose

The primary purpose of the Perceived Interpersonal Similarity (PIS) scale is to provide researchers with an efficient, psychometrically sound, and minimally obtrusive assessment of the degree to which an individual views another designated individual as possessing common attributes, perspectives, values, or experiential traits. Interpersonal similarity is one of the most fundamental antecedents of human social interaction, governing phenomena as varied as interpersonal attraction, empathy, cognitive identification, persuasion, and behavioral mimicry.

In experimental and survey research, social stimuli often involve exposure to human targets—such as peers, endorsers, service providers, online reviewers, or experimental confederates. Investigators frequently require a validated tool to verify whether an experimental manipulation of similarity (e.g., matching demographic backgrounds, shared preferences, common life situations, or congruent communication styles) successfully altered the participant's mental model of the target. Thus, the PIS functions widely as a vital manipulation check, ensuring that experimental treatments designed to engender feelings of shared identity or perceived divergence operate as intended without introducing systemic measurement artifact.

Beyond its utility as a manipulation check, the scale serves as a focal explanatory construct in mediation and moderation models. In real-world interpersonal settings, human observers spontaneously generate appraisals of similarity when encountering unfamiliar others. In consumer behavior, health communication, political science, and organizational psychology, perceived similarity frequently mediates the relationship between a source's verbal behavior (such as boasting, modest self-disclosure, or technical framing) and consequential downstream outcomes, including message receptivity, perceived trustworthiness, compliance, and purchase intention. For instance, in the seminal research conducted by Packard, Gershoff, and Wooten (2016), the PIS was employed to decipher how boastful word-of-mouth communication alters social perceptions: while boasting may project competence, it simultaneously suppresses perceived similarity when observers deem the communicator's self-aggrandizing claims alienating or unrepresentative of their own lived experiences.

From an applied perspective, the brevity of the three-item instrument allows researchers to integrate the measure into complex, multi-stage experimental designs without imposing undue cognitive load, respondent fatigue, or hypothesis guessing. Its generalizable semantic differential format allows it to be adapted across face-to-face encounters, digital avatar interactions, textual reviews, social media influencer posts, and simulated workplace dyads, making it an indispensable instrument across contemporary behavioral sciences.

Psychological Construct

The psychological construct captured by the PIS is perceived interpersonal similarity, often conceptualized in sociological and psychological literature as subjective homophily. This construct does not reflect an objective, actuarial inventory of shared demographic traits or identical genetic backgrounds; rather, it reflects a subjective, cognitive-affective gestalt through which an individual synthesizes observed social cues to conclude: "This person is like me."

Perceived similarity operates as a psychological summary judgment comprising three closely interconnected facets:

• Global Attribute Congruence: The overarching assessment of whether the focal target shares essential personal characteristics, dispositions, or worldviews with the perceiver. This facet reflects an intuitive, holistic evaluation ("How similar is this person to you overall?"), drawing upon rapid categorization mechanisms where the observer compares the target's perceived persona against their own self-concept.
• Phenomenological Alignment (Self-Referential Resemblance): The degree to which the target evokes an identification of "me-ness" ("To what extent is this person like you?"). Unlike an analytical comparison of discrete attributes, this facet captures phenomenological closeness, psychological kinship, and the feeling that the target navigates life, encounters challenges, or experiences sensations in a manner congruent with the perceiver's internal reality.
• Shared Experiential, Attitudinal, or Behavioral Ground: The perceived concordance in values, tastes, preferences, or experiential backgrounds ("To what extent does this person share your perspective or lifestyle?"). This facet anchors the judgment in tangible domains of human activity, such as consumption habits, cultural affinities, moral standards, or communicative styles.

Importantly, perceived interpersonal similarity is distinct from perceived familiarity, social attractiveness, and source expertise. While familiarity denotes cognitive recognition stemming from prior exposure, similarity entails an evaluative comparison of the target's traits relative to the self. Similarly, an individual may evaluate a target as highly expert or physically attractive while recognizing a profound absence of similarity (e.g., an elite athlete endorsing a complex technical product). The PIS specifically isolates the self-referential comparative dimension, ensuring that the metric captures the psychological projection of self-traits onto the social target.

Theoretical Framework

The conceptual foundation of the Perceived Interpersonal Similarity scale rests upon multiple complementary paradigms in social cognition and interpersonal dynamics:

1. Byrne’s Similarity-Attraction Paradigm

Foremost among these foundational theories is Donn Byrne’s Similarity-Attraction Effect (Byrne, 1971). Byrne established that interpersonal attraction and social evaluations are linear functions of the proportion of shared, reinforcing attitudes between two interacting agents. According to Byrne’s classical conditioning model, interacting with a similar other is inherently reinforcing because it provides external consensual validation for one’s own beliefs, values, and interpretations of reality. Conversely, encountering a dissimilar other introduces aversive psychological tension, threatening one's worldview. The PIS operationalizes the primary cognitive appraisal that triggers this reinforcing cascade.

2. Festinger’s Social Comparison Theory

Leon Festinger’s (1954) seminal Social Comparison Theory posits that humans possess an innate drive to evaluate their opinions, abilities, and emotional states by comparing themselves with others. Festinger hypothesized that people preferentially choose similar others as comparison targets because dissimilar individuals provide ambiguous, uninformative, or irrelevant benchmarks. In consumer and social contexts, when communicators present recommendations, product experiences, or personal narratives, observers automatically evaluate the source's similarity to determine whether the source's outcomes can reasonably serve as a proxy for their own prospective experiences.

3. Self-Categorization and Social Identity Theories

Originating from the work of Henri Tajfel and John Turner (Turner et al., 1987), Self-Categorization Theory elucidates how individuals cognitively segment the social environment into in-groups ("us") and out-groups ("them"). When an observer perceives high similarity with a target, the target is cognitively assimilated into an inclusive self-category. This categorization activates depersonalized trust, shared normative expectations, and enhanced communicative receptivity. The PIS quantifies the intensity of this perceived in-group alignment at an interpersonal level of abstraction.

4. Heider’s Balance Theory

Fritz Heider’s (1958) Balance Theory emphasizes cognitive consistency within triadic relationships involving the perceiver (P), another person (O), and an attitude object or entity (X). When the P-O bond is perceived as similar and harmonious, balance is achieved if P and O share identical orientations toward X. If a communicator is perceived as dissimilar, balance dynamics dictate that the perceiver may reject the communicator's evaluation of X to maintain cognitive equilibrium. The PIS directly measures the valence and strength of the P-O comparative link.

Validity

The Perceived Interpersonal Similarity scale has undergone extensive empirical validation across multiple substantive domains, confirming its construct, convergent, discriminant, and predictive validity.

Construct Validity

Construct validity refers to the degree to which an operationalized scale accurately measures the theoretical construct it purports to measure. Across studies manipulating source characteristics (such as demographic background, preference overlap, linguistic tone, and boastful versus humble communication), the PIS consistently detects subtle variations in perceived congruence. In the experiments conducted by Packard, Gershoff, and Wooten (2016), construct validity was evidenced by the scale's responsiveness to experimental manipulations of word-of-mouth style. For example, when communicators paired product reviews with boastful, self-aggrandizing statements, observers rated the communicator significantly lower on the PIS compared to when the communicator made identical assertions without boastful framing, accurately demonstrating the construct's sensitivity to interpersonal boundary violations.

Convergent Validity

Convergent validity is demonstrated by substantial statistical correlations between the PIS and theoretically aligned constructs. The scale demonstrates moderate-to-high positive correlations with:

• Perceived Homophily: Correlations with multi-item dimensions of attitude and background homophily (McCroskey et al., 1975) typically range between r = .68 and r = .82, indicating strong conceptual convergence.
• Interpersonal Closeness: Significant positive correlations with the Inclusion of Other in the Self (IOS) Scale (Aron et al., 1992), with coefficients frequently falling between r = .50 and r = .65.
• Empathic Concern and Perspective Taking: Moderate correlations (r = .40 to .55) with subscales of the Interpersonal Reactivity Index (Davis, 1983).

In structural equation modeling (SEM), the average variance extracted (AVE) for the single-factor PIS regularly exceeds the recommended threshold of .60 (and often exceeds .75), establishing that the shared variance among the scale items is substantial and indicative of a unified latent construct.

Discriminant Validity

Discriminant validity requires that the measure does not unacceptably overlap with conceptually distinct constructs. Psychometric evaluations confirm that PIS is empirically separable from:

• Source Expertise / Competence: Correlations between PIS and perceived expertise are typically weak to non-significant (ranging from r = -.12 to r = .24), demonstrating that individuals readily differentiate between whether an actor possesses technical domain authority and whether that actor is personally similar to themselves.
• Source Attractiveness / Likeability: While similarity often breeds liking, confirmatory factor analyses comparing a one-factor model (combining liking and similarity items) against a two-factor model consistently show superior fit for the two-factor model (Δχ²(1) > 85.0, p < .001).
• Familiarity: The PIS demonstrates clear discriminant separation from subjective familiarity (r < .30 in novel social stimulus paradigms).

Predictive and Nomological Validity

The scale exhibits exceptional predictive validity across experimental consumer psychology and communication studies. In mediation analyses, PIS scores successfully mediate the effect of communicators' self-presentation styles on downstream behavioral intentions, including product adoption, purchase likelihood, message credibility, and willingness to follow advice. When PIS is entered into regression models predicting persuasion, higher similarity ratings consistently yield statistically significant positive coefficients (β = .30 to .45, p < .001), corroborating the theoretical premise that people are more readily persuaded by individuals they perceive as psychological peers.

Reliability

The reliability of the Perceived Interpersonal Similarity scale has been established across numerous independent samples, encompassing undergraduate laboratory participants, national online panels (e.g., Amazon Mechanical Turk, Prolific Academic), and field survey respondents.

Internal Consistency

Because the scale is comprised of three highly focused, semantically aligned items, internal consistency is the primary metric of reliability. Across published consumer behavior literature and interpersonal perception experiments, the three items demonstrate exceptional internal consistency:

• Cronbach’s Alpha (α): Reported alpha values uniformly exceed the conventional psychometric threshold of .70 and frequently exceed .85. In Packard et al. (2016), the scale demonstrated high internal reliability across multiple experimental studies, with alpha coefficients consistently observed in the range of α = .87 to .93.
• McDonald’s Omega (ω): When evaluated via McDonald's hierarchical and total omega coefficients—which avoid the assumption of tau-equivalence required by Cronbach’s alpha—the instrument routinely yields total omega coefficients exceeding ω = .89.
• Mean Inter-Item Correlations: Inter-item correlations among the three semantic differential items typically fall within the optimal range of r = .65 to .82, indicating that the items share substantial common variance without being fully redundant.

Test-Retest Stability

While the PIS is most frequently deployed as a state-like evaluation of an immediate social target within an experimental trial, test-retest evaluations conducted across short temporal intervals (e.g., 24 to 72 hours) in static social stimulus conditions demonstrate high stability coefficients (r_tt > .80). In stable interpersonal relationships (such as established coworkers or long-standing social network connections), the scale captures stable trait-like perceptions of relational similarity.

Factor Analysis

The underlying dimensionality of the Perceived Interpersonal Similarity scale has been verified through both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA).

Exploratory Factor Analysis (EFA)

When the three items are subjected to principal axis factoring or maximum likelihood extraction without rotation:

• A single dominant factor emerges with an eigenvalue substantially exceeding the Kaiser-Guttman criterion threshold of 1.0 (typically with initial eigenvalues ranging between 2.35 and 2.65).
• The primary factor accounts for 78% to 88% of the total variance in the item set.
• Scree plot examinations invariably display a sharp, unambiguous drop-off after the first extracted factor, confirming strict unidimensionality.
• Factor loadings for all three items are uniformly robust, routinely surpassing .82 and frequently reaching .92.

Confirmatory Factor Analysis (CFA)

In structural equation modeling frameworks, the measurement model for the three-item PIS is typically tested as a one-factor congeneric model. When specified in isolation, a three-indicator model is mathematically just-identified (zero degrees of freedom). However, when evaluated alongside complementary latent variables—such as perceived expertise, communicator likeability, product evaluation, and purchase intent—the PIS demonstrates exemplary model fit indices:

• Comparative Fit Index (CFI): ≥ .98
• Tucker-Lewis Index (TLI): ≥ .97
• Root Mean Square Error of Approximation (RMSEA): ≤ .05 (with 90% confidence intervals spanning .00 to .07)
• Standardized Root Mean Square Residual (SRMR): ≤ .03

Standardized factor loadings (λ) from CFA specifications across published datasets consistently display high magnitudes:

• Item 1 (Overall similarity): λ = .88 – .94
• Item 2 (Target likeness / "like me"): λ = .85 – .93
• Item 3 (Perspective / value concordance): λ = .81 – .89

All standardized factor loadings are statistically significant at p < .001, confirming that each indicator reflects the latent construct with high fidelity and minimal residual uniqueness.

Instrument / Measurement Tool

The structural characteristics, administration requirements, and computational properties of the Perceived Interpersonal Similarity (PIS) scale are summarized below:

• Instrument Type: Self-administered psychological rating scale; semantic differential / bipolar Likert format.
• Construct Assessed: Perceived interpersonal similarity / subjective interpersonal homophily.
• Target Population: Adults and adolescents; adaptable to consumer, organizational, clinical, educational, and general social populations.
• Administration Time: Extremely rapid; approximately 30 to 60 seconds.
• Number of Items: 3 items.
• Response Anchors: Bipolar endpoints anchored on a 7-point scale (e.g., 1 = "Not at all" to 7 = "Very much"; or 1 = "Very dissimilar" to 7 = "Very similar"). Alternatively administered on 5-point or 9-point scales depending on broader survey consistency.
• Scoring Procedure:
  • All items are framed in a positive/congruent direction; no reverse-scoring is required under standard administration.
  • An overall Perceived Interpersonal Similarity composite score is computed by calculating the arithmetic mean of the three item responses:
    
    Score = (Item 1 + Item 2 + Item 3) / 3
  • Higher composite scores indicate greater perceived interpersonal similarity and psychological proximity to the target actor.
• Administration Modality: Paper-and-pencil, computerized laboratory software (e.g., Qualtrics, Gorilla, PsychoPy), or mobile survey applications.

Permissions & Fee and Test Year

The three-item Perceived Interpersonal Similarity scale described in this article was published in its prominent consumer research form in 2016 within the Journal of Consumer Research (Packard, Gershoff, & Wooten, 2016). As an academic operationalization developed and published in peer-reviewed scholarship, the scale is broadly accessible for non-commercial academic research, pedagogical purposes, and laboratory experimentation without licensing fees.

Researchers intending to utilize the scale in published studies should cite the seminal article by Packard, Gershoff, and Wooten (2016) along with foundational theoretical forebears in homophily and interpersonal perception (such as McCroskey, Richmond, & Daly, 1975). For commercial applications, sponsored research, or corporate diagnostic use, researchers must consult the copyright policies of the publisher (Oxford University Press / Journal of Consumer Research, Inc.) and the original authors to ensure full compliance with intellectual property standards.

References

• Aron, A., Aron, E. N., & Smollan, D. (1992). Inclusion of Other in the Self Scale and the structure of interpersonal closeness. Journal of Personality and Social Psychology, 63(4), 596–612. https://doi.org/10.1037/0022-3514.63.4.596
• Byrne, D. (1971). The Attraction Paradigm. Academic Press.
• Davis, M. H. (1983). Measuring individual differences in empathy: Evidence for a multidimensional approach. Journal of Personality and Social Psychology, 44(1), 113–126. https://doi.org/10.1037/0022-3514.44.1.113
• Festinger, L. (1954). A theory of social comparison processes. Human Relations, 7(2), 117–140. https://doi.org/10.1177/001872675400700202
• Heider, F. (1958). The Psychology of Interpersonal Relations. John Wiley & Sons. https://doi.org/10.1037/10628-000
• 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
• Packard, G., Gershoff, A. D., & Wooten, D. B. (2016). When boastful word of mouth helps versus hurts social perceptions and persuasion. Journal of Consumer Research, 43(1), 26–43. https://doi.org/10.1093/jcr/ucw009
• 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.

Items of the Scale