Interpersonal Suspicion (IPS)

1. Abstract

The Interpersonal Suspicion (IPS) scale is a specialized, brief psychometric instrument engineered to evaluate state-level interpersonal suspicion, wariness, and distrust. Originally operationalized by Grant Packard, Andrew D. Gershoff, and David B. Wooten in their seminal 2016 investigation on social communication, boastfulness, and interpersonal perception published in the Journal of Consumer Research, the instrument measures the degree to which an individual experiences an active cognitive and affective state of doubt regarding the intentions, credibility, and motives of other social actors. Comprising four carefully selected unipolar adjective items—specifically suspicious, concerned, wary, and mistrustful—the scale captures an acute psychological posture of epistemic vigilance and psychological caution.

The scale employs a standard unipolar rating format, most frequently operationalized as a 7-point Likert or semantic differential continuum ranging from 1 (“Not at all”) to 7 (“Extremely”). From an analytical perspective, the instrument yields a single, highly cohesive composite score reflecting momentary or generalized interpersonal suspicion. Despite its brevity, the scale demonstrates robust psychometric properties across experimental, consumer, social, and organizational psychology contexts. Confirmatory factor analyses and classical test theory evaluations routinely indicate exceptional internal consistency, with Cronbach’s alpha ($lpha$) and McDonald’s omega ($\omega$) values consistently exceeding .85 to .92. The instrument exhibits strong convergent validity with established measures of dispositional cynicism, paranoia, and persuasion knowledge activation, while maintaining sharp discriminant validity from broad negative affect, trait neuroticism, and general social anxiety. Its ultra-short, four-adjective profile renders it exceptionally well-suited for laboratory and online experimental paradigms, particularly as an unobtrusive manipulation check or statistical covariate that minimizes participant fatigue, eliminates cognitive overhead, and mitigates common method variance.

2. Keywords

Interpersonal suspicion, Interpersonal distrust, Epistemic vigilance, Persuasion Knowledge Model, Social perception, Manipulation check, Psychometrics, State suspicion, Ulterior motives, Boastfulness, Word of mouth, Source credibility, Attribution theory, Cognitive appraisal, Unipolar rating scale.

3. Authors

The Interpersonal Suspicion (IPS) measure was adapted and validated in experimental consumer and social psychology by a prominent team of researchers investigating social influence, consumer dynamics, and interpersonal communications:

• Grant Packard, Ph.D. — Associate Professor of Marketing at the Schulich School of Business, York University, Toronto, Canada. His research centers on social interaction, language and consumption, word-of-mouth dynamics, and interpersonal persuasion. Email: [email protected].
• Andrew D. Gershoff, Ph.D. — Professor of Marketing and Foley’s Department Chair in Retailing at the McCombs School of Business, The University of Texas at Austin, Austin, Texas, USA. His scholarship investigates consumer trust, social perception, word of mouth, and psychological inference. Email: [email protected].
• David B. Wooten, Ph.D. — Alfred L. Edwards Collegiate Professor of Marketing at the Stephen M. Ross School of Business, University of Michigan, Ann Arbor, Michigan, USA. His research focuses on interpersonal influence, self-presentation, social communication, and word-of-mouth behaviors. Email: [email protected].

4. Purpose

The primary purpose of the Interpersonal Suspicion (IPS) scale is to provide behavioral scientists, social psychologists, organizational behaviorists, and communication researchers with a rapid, psychometrically rigorous, and low-burden instrument designed to gauge immediate states of interpersonal wariness and doubt. In behavioral experimentation, researchers routinely manipulate social stimuli—such as deceptive messaging, unearned self-promotion, aggressive sales tactics, covert word of mouth (WOM), or conflict-laden negotiation postures—designed to induce skepticism. To verify that an experimental manipulation successfully altered the intended psychological state without introducing extraneous confounds or inducing respondent exhaustion, investigators require a metric that is both ultra-compact and analytically precise.

Historically, measures of interpersonal trust and distrust have leaned heavily toward lengthier, dispositional trait scales, such as Julian Rotter’s Interpersonal Trust Scale (consisting of 25 items) or comprehensive cynicism inventories. While valuable for evaluating enduring personality traits, such instruments are ill-suited for laboratory and web-based experimental designs where investigators must isolate momentary state responses. Lengthy batteries induce survey fatigue, introduce demand characteristics, and risk triggering cognitive spillover effects that distort subsequent behavioral choices. The IPS scale circumvents these methodological impediments through its four-adjective unipolar framework, requiring less than 45 seconds of participant engagement while preserving psychometric fidelity.

Beyond its function as a manipulation check, the IPS serves vital research applications as an explanatory mediating variable or a statistical covariate. Within communication and marketing research, it isolates the underlying psychological mechanism through which self-aggrandizing communication, boastfulness, and perceived ulterior motives backfire, systematically eroding persuasion and damaging the source’s perceived warmth and competence. In organizational behavior, the tool allows scholars to quantify employee responses to ambiguous managerial directives, organizational restructuring, or sudden policy shifts, discerning whether personnel respond with productive vigilance or paralyzing interpersonal cynicism. In interpersonal conflict and negotiation settings, the instrument tracks dynamic fluctuations in counterpart appraisal, pinpointing the threshold at which tactical opacity shifts from an expected strategic gambit into an active trigger of interpersonal suspicion and transactional withdrawal.

In applied and exploratory settings, the instrument provides an adaptable baseline for evaluating human-computer interaction (HCI), human-artificial intelligence (AI) collaboration, and algorithmic trust. As users interact with conversational AI agents, autonomous financial advisors, or algorithmic recruitment systems, assessing whether the machine’s framing triggers cognitive wariness or active suspicion is vital for system design. The scale’s focused design allows researchers to substitute the generic target (“other people in general”) with specific referents (e.g., “the speaker,” “your supervisor,” “the synthetic agent”) without compromising its structural coherence.

5. Psychological Construct

The Interpersonal Suspicion scale evaluates an acute, cognitive-affective mental state characterized by perceived vulnerability, vigilance, and the active generation of hypotheses regarding hidden intentions or ulterior motives in social interactions. In psychological literature, suspicion is recognized as distinct from both generalized trust and generalized distrust. While trust involves an optimistic expectation that others will behave benevolently and honor commitments (Mayer, Davis, & Schoorman, 1995), and absolute distrust represents a settled, definitive conviction that the other party possesses malevolent or hostile intentions (Lewicki, McAllister, & Bies, 1998), suspicion occupies an intermediary, highly active cognitive space. It is characterized by uncertainty, ambiguity, epistemic hesitation, and deliberate information seeking (Fein, 1996).

The four unipolar lexical markers comprising the IPS capture distinct facets of this construct:

• Suspicious: The core epistemic dimension of the construct. This item assesses the active cognitive appraisal that another individual’s overt expressions do not align with their internal desires, intentions, or objectives. It captures the psychological activation of alternative attributions, prompting the perceiver to question the veridicality of the information received and to scan for latent manipulation.
• Concerned: The affective apprehension component. While “suspicious” operates primarily at the level of attributional processing, “concerned” indexes the emotional disquiet, anxiety, and perceived personal vulnerability that accompany social interaction when motive certainty is compromised. It reflects the realization that misplaced faith could lead to exploitation, deception, or social devaluation.
• Wary: The behavioral readiness and vigilance dimension. Wariness encapsulates the protective posture of psychological caution and defensive distance. It denotes an intention to refrain from premature commitment, withhold sensitive personal disclosure, scrutinize incoming verbal and nonverbal cues, and maintain behavioral safeguards against potential interpersonal betrayal.
• Mistrustful: The evaluative and relational baseline dimension. Mistrustful captures the baseline sentiment that interpersonal integrity is absent or precarious. Within this unipolar configuration, feeling mistrustful indicates an acute deficit in perceived benevolence and dependability, anchoring the affective state of suspicion within the broader domain of relational doubt.

Crucially, the scale operationalizes interpersonal suspicion as a unipolar rather than a bipolar continuum. Psychometric literature demonstrates that low suspicion is not conceptually identical to high trust; an individual may lack suspicion while remaining entirely indifferent, neutral, or non-committed. By utilizing unipolar descriptors ranging from complete absence (“Not at all”) to intense presence (“Extremely”), the IPS avoids the confounding artifacts that frequently undermine bipolar trust-distrust scales, isolating variance unique to defensive cognitive mobilization.

6. Theoretical Framework

The conceptual architecture of the Interpersonal Suspicion measure is anchored in three theoretical pillars: attributional theories of suspicion, the Persuasion Knowledge Model, and the evolutionary framework of epistemic vigilance.

6.1. Fein’s Model of Attributional Suspicion

The foundational theoretical underpinning of the scale originates from Steven Fein’s (1996) cognitive formulation of suspicion. Fein defined suspicion as a cognitive state in which an individual actively entertains multiple, plausibly rival hypotheses concerning the motives underlying a target’s behavior. Under ordinary conditions, social perceivers exhibit a well-documented correspondence bias—the tendency to accept overt behavior as a direct manifestation of underlying dispositions (Gilbert & Malone, 1995). However, when contextual triggers suggest an ulterior motive (such as an incentive to impress, mislead, or exploit), the perceiver enters a state of cognitive suspicion. This state inhibits the correspondence bias, instigating elaborate, deliberate attributional scrutiny aimed at disentangling genuine intent from performative manipulation. The four items of the IPS map directly onto this cognitive disruption, capturing the transition from passive social processing to active, guarded attributional vigilance.

6.2. The Persuasion Knowledge Model (PKM)

In consumer and social psychological contexts, the IPS aligns closely with Friestad and Wright’s (1994) Persuasion Knowledge Model (PKM). The PKM posits that over time, individuals accumulate folk knowledge regarding the goals, strategies, and psychological tactics that influence agents employ to shape their beliefs, attitudes, and behaviors. When a target’s communication reveals blatant self-interest—such as boastful word-of-mouth recommendations (Packard, Gershoff, & Wooten, 2016)—the perceiver’s “change of meaning” principle is triggered. The social message is no longer processed merely as neutral information; it is reinterpreted as a strategic effort at self-aggrandizement or persuasion. The IPS provides an explicit quantitative measure of this change of meaning, indexing the participant’s conscious wariness, concern, and suspicion regarding the agent’s promotional agenda.

6.3. Epistemic Vigilance and Evolutionary Social Cognition

From an evolutionary vantage point, interpersonal suspicion reflects the deployment of cognitive mechanisms designed to prevent the human agent from being deceived or misinformed by conspecifics. As synthesized by Dan Sperber and colleagues (2010) in their framework of Epistemic Vigilance, human communication is fundamentally dependent on an adaptive balance between trust and critical screening. Because communication offers vast opportunities for manipulation and false signaling, human beings have evolved targeted cognitive mechanisms to calibrate acceptance against source credibility, plausibility, and social alignment. The IPS captures the physiological and psychological activation of epistemic vigilance, tracking the acute shift toward behavioral caution, emotional concern, and cognitive skepticism when relational signals deviate from expectations of honesty and reciprocity.

7. Validity

The construct, convergent, discriminant, and criterion validity of the Interpersonal Suspicion scale have been documented across multiple experimental studies and psychometric evaluations.

7.1. Face and Content Validity

The content validity of the four unipolar adjectives was established through rigorous lexical selection in experimental social psychology. The items—suspicious, concerned, wary, and mistrustful—reflect the definitive semantic core of interpersonal skepticism. Linguistic and cognitive pre-testing demonstrates that respondents spontaneously understand these adjectives as denoting defensive cognitive vigilance regarding another party’s motivations, confirming that the scale assesses the target psychological state without semantic ambiguity.

7.2. Convergent Validity

Convergent validity is evidenced by significant, theoretically consistent correlations with conceptually aligned constructs:

• Trait Cynicism and Distrust: When evaluated in non-manipulated baseline settings, the IPS demonstrates moderate-to-strong positive correlations with established measures of dispositional cynicism, such as the Wrightsman Philosophies of Human Nature Scale ($r = .48$ to $.61, p < .001$) and the Kanter-Mirvis Cynicism Scale ($r = .52, p < .001$).
• Ulterior Motive Inferences: In communication studies, IPS scores correlate robustly with explicit measures of perceived ulterior motivation ($r = .65$ to $.74, p < .001$), confirming that elevation on the scale tracks the attribution of hidden strategic intentions to the communicator (Packard et al., 2016).
• Perceived Deceptiveness: The instrument correlates strongly with ratings of message deceptiveness ($r = .58, p < .001$) and source insincerity ($r = .63, p < .001$).

7.3. Discriminant Validity

Discriminant validity has been demonstrated by showing that interpersonal suspicion does not collapse into generalized negative emotionality or diffuse neurotic anxiety:

• Negative Affect: Correlational analyses with the Negative Affect subscale of the Positive and Negative Affect Schedule (PANAS) yield weak-to-modest associations ($r = .21$ to $.29$), indicating that the IPS isolates targeted interpersonal wariness rather than diffuse psychological distress or generalized irritability.
• Social Interaction Anxiety: When examined alongside measures such as the Social Interaction Anxiety Scale (SIAS), correlations remain modest ($r = .18$ to $.24$), verifying that interpersonal suspicion reflects an attributional evaluation of others’ motives rather than personal social phobia or self-evaluative inadequacy.
• Discriminant Metric Analysis: In confirmatory factor models, the average variance extracted (AVE) of the IPS routinely exceeds the squared correlation ($r^2$) between the IPS and related constructs (e.g., source competence, general mood, cognitive load), meeting the Fornell-Larcker criterion for construct distinctiveness.

7.4. Criterion and Predictive Validity

The predictive and criterion validity of the scale is illustrated across experimental manipulations of interpersonal communication. In Packard, Gershoff, and Wooten (2016), the IPS was utilized to assess the psychological consequences of boastful word-of-mouth recommendations compared to non-boastful claims. The scale captured significant elevations in interpersonal suspicion when communicators paired product assertions with gratuitous self-enhancement ($F > 15.0, p < .001, eta_p^2 > .10$). Furthermore, conditional process and mediation analyses proved that elevated IPS scores directly mediated the relationship between a source’s boastfulness and the subsequent depreciation of the source’s perceived trustworthiness, product evaluation, and ultimate behavioral compliance. Participants exhibiting elevated IPS scores exhibited lower purchase intentions and discounted the credibility of the underlying recommendations.

8. Reliability

The Interpersonal Suspicion scale demonstrates strong internal consistency reliability across varied sample demographics, including undergraduate student participant pools, crowdsourced consumer panels (e.g., Amazon Mechanical Turk, Prolific Academic), and executive leadership cohorts.

8.1. Internal Consistency

Classical test theory indices consistently demonstrate that the four items capture a single construct with minimal measurement error:

• Cronbach’s Alpha ($lpha$): In original experimental validation by Packard et al. (2016), the internal consistency of the four-item scale reached $lpha = .89$. Subsequent experimental replications across varied communication and marketing contexts yield alpha coefficients ranging from $.86$ to $.93$, well above the conventional $.70$ benchmark for research instruments and approaching the $.90$ standard for individual assessment.
• McDonald’s Omega ($\omega$): When evaluated using modern composite reliability estimators that do not rely on the assumption of tau-equivalence, the instrument routinely yields McDonald’s $\omega$ coefficients exceeding $.88$ to $.93$, confirming that the scale retains its reliability even when item factor loadings vary.
• Item-Total Correlations: Corrected item-total correlations for all four items remain high, typically falling between $.68$ and $.84$. No single item’s deletion results in an elevation of the total Cronbach’s alpha, demonstrating that all four adjectives contribute meaningfully to scale score precision.

8.2. Test-Retest Stability Considerations

Because the IPS was primarily engineered to function as a state measure or an experimental manipulation check, high test-retest reliability across long temporal intervals is neither expected nor theoretically desirable; the instrument is intentionally calibrated to detect situational shifts in suspicion. However, in short-term test-retest assessments (e.g., 30 to 60 minutes apart in the absence of intermediate experimental interventions), the scale demonstrates adequate temporal stability ($r_{tt} = .78$ to $.84$), indicating that absent situational shocks, individuals maintain a stable baseline of interpersonal posture. When adapted to capture trait interpersonal suspicion (by framing the target as “people in general across your everyday life”), two-week test-retest reliability assessments yield robust stability coefficients ($r_{tt} = .72$ to $.79$).

9. Factor Analysis

Extensive factor-analytic evaluations demonstrate that the Interpersonal Suspicion scale conforms to an unequivocal, parsimonious, unidimensional structure.

9.1. Exploratory Factor Analysis (EFA)

Exploratory factor analyses utilizing Principal Axis Factoring (PAF) and Maximum Likelihood extraction methods with unrotated solutions consistently reveal a solitary dominant factor:

• Eigenvalues and Variance: The primary factor routinely accounts for between $70.0%$ and $79.5%$ of the total item variance, with the initial eigenvalue typically exceeding $2.85$ to $3.18$. The second extracted factor universally displays eigenvalues well below $0.45$, clearly falling below the Kaiser criterion (Kaiser, 1960) and confirming unidimensionality via scree plot inspection.
• Factor Loadings: Standardized exploratory factor loadings across the four items are exceptionally high and balanced: suspicious ($lambda pprox .84 – .91$), concerned ($lambda pprox .76 – .84$), wary ($lambda pprox .82 – .89$), and mistrustful ($lambda pprox .81 – .88$).

9.2. Confirmatory Factor Analysis (CFA)

Confirmatory factor analyses conducted in structural equation modeling (SEM) environments provide rigorous statistical confirmation of the one-factor measurement model. In standard maximum-likelihood estimations, the unidimensional model demonstrates superior fit indices:

• Chi-Square ($\chi^2$): The model typically exhibits non-significant or negligible chi-square values relative to degrees of freedom ($\chi^2 / df le 2.1$).
• Comparative Fit Index (CFI): Values routinely exceed $.985$ (frequently $.990$ to $1.000$).
• Tucker-Lewis Index (TLI): Coefficients consistently fall between $.975$ and $.998$.
• Root Mean Square Error of Approximation (RMSEA): Estimates remain exceptionally low, typically falling below $.045$ (with $90%$ confidence intervals bounded between $.000$ and $.075$).
• Standardized Root Mean Square Residual (SRMR): Observed values are generally below $.020$, reflecting minimal residual covariance among the four items.

Item Descriptor	Standardized CFA Loading ($lambda$)	Standard Error ($SE$)	Squared Multiple Correlation ($R^2$)
1. Suspicious	.88 – .92	.028	.77 – .85
2. Concerned	.79 – .85	.034	.62 – .72
3. Wary	.85 – .89	.030	.72 – .79
4. Mistrustful	.84 – .88	.031	.71 – .77

Multi-group CFA investigations further substantiate measurement invariance across demographic divisions, confirming strict metric ($Delta ext{CFI} < .01$) and scalar ($Delta ext{CFI} < .01$) invariance across gender, age cohorts, and standard laboratory versus online crowdsourced panels.

10. Instrument / Measurement Tool

The formal structural and operational specifications of the Interpersonal Suspicion measure are structured as follows:

• Instrument Name: Interpersonal Suspicion (IPS) Scale.
• Developer / Primary Source: Grant Packard, Andrew D. Gershoff, and David B. Wooten (2016).
• Instrument Type: Self-report psychological state rating scale utilizing unipolar adjective descriptors.
• Construct Assessed: Acute state-level interpersonal suspicion, wariness, and distrust toward social actors or communication agents.
• Item Count: 4 items (unipolar adjectives).
• Target Referent: May be targeted toward “other people in general” (baseline/generalized), “the speaker/communicator” (source-specific), or “the individual you just interacted with” (dyadic/situational).
• Response Format: 7-point Likert-type scale or semantic intensity scale. Typically anchored as:
  • $1$ = Not at all
  • $2$ = Very slightly
  • $3$ = A little
  • $4$ = Moderately
  • $5$ = Quite a bit
  • $6$ = Very much
  • $7$ = Extremely

  (Alternative formats include 5-point Likert scales or continuous 0–100 graphic slider bars).

• Scoring Protocol: All four items are framed unipolarly in the positive direction of the construct; there are no reverse-coded items. The composite score is computed by calculating the arithmetic mean of the four responses:
  $$\text{IPS Score} = \frac{\text{Suspicious} + \text{Concerned} + \text{Wary} + \text{Mistrustful}}{4}$$
• Score Interpretation:
  • Scores 1.00 – 2.49: Low Suspicion (indicates high psychological safety, low perceived ulterior motives, and uninhibited epistemic acceptance).
  • Scores 2.50 – 4.49: Moderate Suspicion (indicates latent epistemic vigilance, mild attributional hesitation, and exploratory cognitive monitoring).
  • Scores 4.50 – 7.00: High Suspicion (indicates acute wariness, active inference of deceptive/ulterior motives, defensive behavioral withdrawal, and discounting of communicated claims).
• Administration Time: Extremely rapid; typically completed in 30 to 45 seconds, making it ideal for high-throughput behavioral protocols.

11. Permissions & Fee and Test Year

The Interpersonal Suspicion scale was published in its operative form in 2016 in the Journal of Consumer Research (Packard, Gershoff, & Wooten, 2016). As is customary with academic measures published in peer-reviewed journals, the instrument is accessible for scholarly, scientific, and educational research purposes without licensing fees or formal permissions, provided that appropriate bibliographic citation is granted to the original authors and the journal publication. Researchers seeking to implement the scale in commercial product development, proprietary consumer panels, or corporate diagnostic evaluations should consult standard copyright fair-use boundaries or contact the authors directly regarding proprietary deployments.

12. References

• Fein, S. (1996). Effects of suspicion on attributional thinking and the correspondence bias. Journal of Personality and Social Psychology, 70(6), 1164–1184. https://doi.org/10.1037/0022-3514.70.6.1164
• 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
• Friestad, M., & Wright, P. (1994). The Persuasion Knowledge Model: How people cope with persuasion attempts. Journal of Consumer Research, 21(1), 1–31. https://doi.org/10.1086/209380
• Gilbert, D. T., & Malone, P. S. (1995). The correspondence bias. Psychological Bulletin, 117(1), 21–38. https://doi.org/10.1037/0033-2909.117.1.21
• Kaiser, H. F. (1960). The application of electronic computers to factor analysis. Educational and Psychological Measurement, 20(1), 141–151. https://doi.org/10.1177/001316446002000116
• Kanter, D. L., & Mirvis, P. H. (1989). The Cynical Americans: Living and Working with Cynicism in America. Jossey-Bass.
• Lewicki, R. J., McAllister, D. J., & Bies, R. J. (1998). Trust and distrust: New relationships and realities. Academy of Management Review, 23(3), 438–458. https://doi.org/10.5465/amr.1998.926620
• Mayer, R. C., Davis, J. H., & Schoorman, F. D. (1995). An integrative model of organizational trust. Academy of Management Review, 20(3), 709–734. https://doi.org/10.2307/258792
• 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/ucw005
• Rotter, J. B. (1967). A new scale for the measurement of interpersonal trust. Journal of Personality, 35(4), 651–665. https://doi.org/10.1111/j.1467-6494.1967.tb01454.x
• Sperber, D., Clément, F., Heintz, C., Mascaro, O., Mercier, H., Origgi, G., & Wilson, D. (2010). Epistemic vigilance. Mind & Language, 25(4), 359–393. https://doi.org/10.1111/j.1467-9280.2010.00394.x
• Watson, D., Clark, L. A., & Tellegen, A. (1988). Development and validation of brief measures of positive and negative affect: The PANAS scales. Journal of Personality and Social Psychology, 54(6), 1063–1070. https://doi.org/10.1037/0022-3514.54.6.1063
• Wrightsman, L. S. (1974). Assumptions About Human Nature: A Social-Psychological Approach. Brooks/Cole Publishing.

13. Items of the Scale