Consumer Susceptibility to Interpersonal Influence

1. Abstract

The Consumer Susceptibility to Interpersonal Influence (CSII) scale is an extensively utilized psychometric instrument developed by William O. Bearden, Richard G. Netemeyer, and Jesse E. Teel in 1989. Designed to assess individual differences in consumer responsiveness to social influence across acquisition and consumption environments, the CSII conceptualizes interpersonal influence as a general trait comprising two distinct dimensions: normative influence and informational influence. Normative influence captures an individual’s inclination to conform to the expectations of reference groups to achieve social rewards, avoid sanctions (utilitarian influence), or reinforce self-identity through association (value-expressive influence). Informational influence reflects the propensity to actively search for and incorporate product information, advice, and consumption evaluations from knowledgeable or trusted others to optimize purchase decisions. Comprising 12 self-report items—eight dedicated to normative influence and four to informational influence—the instrument is historically administered using a 7-point Likert response format ranging from 1 (“Strongly Disagree”) to 7 (“Strongly Agree”), frequently adapted in subsequent consumer research into a 6-point forced-choice format to prevent midpoint neutrality bias. Across decades of empirical investigation, the CSII has demonstrated robust psychometric properties, including high internal consistency (Cronbach’s alpha typically exceeding .80 for informational and .88 for normative dimensions), robust test-retest reliability, cross-cultural validity, and confirmed two-factor confirmatory factor structures across diverse adult and student populations. The instrument remains a foundational framework for investigating social proof, word-of-mouth dynamics, peer influence, brand adoption, and digital social media engagement.

2. Keywords

Consumer Susceptibility to Interpersonal Influence, CSII, normative influence, informational influence, social proof, consumer conformity, reference groups, psychometrics, scale validation, consumer psychology, brand identification, social influence.

3. Authors

The CSII scale was conceptualized, operationalized, and psychometrically validated by a collaborative research team in marketing and consumer behavior at the University of South Carolina:

• William O. Bearden, Ph.D. — Professor Emeritus of Marketing and former Bank of America Chaired Professor of Marketing, Darla Moore School of Business, University of South Carolina, Columbia, SC, USA. Renowned for pioneering contributions to psychometric measurement, consumer socialization, and pricing psychology.
• Richard G. Netemeyer, Ph.D. — Ralph A. Beeton Professor of Free Enterprise, McIntire School of Commerce, University of Virginia, Charlottesville, VA, USA. Widely published authority on psychometric scale development, structural equation modeling, work-family conflict, and behavioral decision-making.
• Jesse E. Teel, Ph.D. — Professor of Marketing, Darla Moore School of Business, University of South Carolina, Columbia, SC, USA. Expert in consumer behavior measurement, marketing communications, and quantitative research methodology.

4. Purpose

Consumer decision-making rarely occurs in social isolation. From routine grocery choices to high-involvement luxury acquisitions, individual choices are intrinsically shaped by perceived social expectations, reference group norms, and observational learning. The primary purpose of the Consumer Susceptibility to Interpersonal Influence (CSII) scale is to provide researchers, organizational psychologists, and consumer strategists with an operationally sound, theoretically grounded, and psychometrically rigorous tool for quantifying the extent to which an individual consumer is susceptible to interpersonal social pressures and information cues.

Prior to the establishment of the CSII in 1989, consumer researchers relied heavily on broad sociological conformity metrics, situational compliance experiments, or fragmented single-item indicators that failed to disentangle distinct social processes. Bearden, Netemeyer, and Teel recognized that social influence manifests across consumer contexts through two theoretically unique pathways: conformity driven by social approval and identity preservation versus decision-making driven by epistemic uncertainty reduction. The CSII was designed to capture this underlying individual-difference trait, functioning as an enduring consumer predisposition rather than a transient, product-specific reaction.

In academic and applied research, the CSII serves multiple critical functions:

• Market Segmentation and Persona Development: Enabling researchers to identify distinct consumer clusters that are either highly impervious to social pressures (autonomous consumers) or acutely reliant on social validation and external endorsements (normative or informational consumers).
• Advertising and Persuasion Strategy: Assisting communicators in determining whether promotional campaigns should emphasize expert testimonials, user ratings, and objective comparisons (effective for high informational susceptibility) or aspirational peer modeling, status signaling, and group affiliation (effective for high normative susceptibility).
• Understanding Digital Word-of-Mouth (eWOM) and Viral Dynamics: Investigating why certain consumers actively seek online reviews, unboxing videos, and influencer recommendations, as well as their propensity to alter purchase intentions based on user-generated content across social networks.
• Socialization and Developmental Studies: Examining the evolution of consumer susceptibility across age cohorts, transitions through adolescence into early adulthood, and changes across generational cohorts facing algorithmic social media environments.

5. Psychological Construct

The CSII measures an enduring personality trait defined by Bearden et al. (1989) as the “need to identify with or enhance one’s image in the opinion of significant others through the acquisition and use of products and brands, the willingness to conform to the expectations of others regarding purchase decisions, and/or the tendency to learn about products and services by observing others or seeking information from others.” This macro-construct operates through two distinct sub-dimensions:

Normative Influence

Normative influence occurs when an individual complies with positive expectations of another person or group. In consumer contexts, this reflects the drive to conform to group standards to achieve social rewards (praise, acceptance, belonging) or evade social sanctions (rejection, ridicule, ostracism). Drawing upon classic psychological frameworks, normative influence encapsulates two intertwined sub-mechanisms:

• Value-Expressive Influence: The consumer’s psychological need to associate with referent groups and express an aligned self-concept. Consumers purchase specific brands or wear particular garments because those items symbolize membership or aspirational alignment with desired peer groups. For example, buying a specific athletic brand not because of technical superiority, but because it projects an active, stylish identity validated by one’s peer circle.
• Utilitarian Influence: Compliance driven by direct perceived consequences. An individual aligns their consumption choices with the explicit or implicit desires of important others (e.g., family members, colleagues, supervisors) to satisfy expectations and maintain relational equilibrium. For instance, selecting business attire that strictly mirrors office convention to avoid unfavorable appraisal.

In the CSII, these two aspects are united within the 8-item normative subscale, as empirical factor analyses consistently demonstrated that value-expressive and utilitarian items load onto a single unified normative factor.

Informational Influence

Informational influence stems from the fundamental human motivation to make accurate, optimal, and rational decisions under conditions of uncertainty. Rather than seeking social approval, consumers high in informational susceptibility look to others as credible sources of evidence regarding objective reality. When consumers possess limited direct experience with a product category, perceive high financial or performance risk, or confront an overwhelming array of technical options, they seek guidance through two operational avenues:

• Direct Search: Proactively querying knowledgeable peers, friends, family members, or acknowledged experts regarding product functionality, durability, and value.
• Observational Learning: Unobtrusively monitoring what knowledgeable others acquire and consume, inferring that widespread adoption reflects product efficacy or superior utility.

Unlike normative influence, which is primarily driven by social evaluation and self-presentation, informational influence is driven by epistemic needs and risk mitigation.

6. Theoretical Framework

The theoretical architecture of the CSII is grounded in the foundational social psychological taxonomy of influence proposed by Morton Deutsch and Harold B. Gerard (1955). Deutsch and Gerard formally distinguished between normative social influence (influence to conform to the positive expectations of another) and informational social influence (influence to accept information obtained from another as evidence about reality), demonstrating experimentally that conformity could be parsed into motivational versus epistemic components.

This taxonomy was subsequently extended into functional reference group theory by Herbert C. Kelman (1958, 1961) in his tripartite model of opinion change: compliance (conforming to obtain favorable reactions), identification (adopting behaviors to establish or maintain a satisfying self-defining relationship to another person or group), and internalization (accepting influence because the induced behavior is congruent with one’s value system and functionally useful). In consumer psychology, C. Whan Park and V. Parker Lessig (1977) operationalized Kelman’s concepts to evaluate reference group influence across product categories, establishing that consumer reliance on groups spans utilitarian, value-expressive, and informational vectors.

Bearden, Netemeyer, and Teel (1989) synthesized these frameworks into individual-difference measurement. They hypothesized that susceptibility to social influence is not solely situational—such as in the classical experiments of Solomon Asch or Muzafer Sherif—but is moderated by a stable psychological trait. This trait is functionally related to broader psychological constructs including self-monitoring (Snyder, 1974), attention to social comparison information (Lennox & Wolfe, 1984), self-esteem (Coopersmith, 1967), and consumer independence. Individuals high in self-monitoring and public self-consciousness demonstrate elevated CSII normative scores, whereas individuals with high consumer self-confidence or high subjective product knowledge exhibit lower informational susceptibility.

7. Validity

The construct, convergent, discriminant, and predictive validity of the CSII scale have been corroborated across dozens of independent empirical investigations worldwide.

Construct and Convergent Validity

During the initial validation process, Bearden et al. (1989) administered the instrument across multiple student and non-student consumer samples (totalling over 800 participants). Convergent validity was established through strong, statistically significant correlations with established instruments measuring conceptually adjacent constructs:

• Positive correlations with Lennox and Wolfe’s (1984) Attention to Social Comparison Information (ATSCI) scale (r values typically between .50 and .65, p < .001).
• Positive correlations with Snyder’s (1974) Self-Monitoring scale (particularly the social conformity factor).
• Positive correlations with interpersonal orientation and public self-consciousness measures.

Discriminant Validity

Discriminant validity was established via average variance extracted (AVE) analyses and distinct pattern correlations. Specifically, the CSII demonstrated negative correlations with consumer self-confidence, self-esteem, and generalized independence (e.g., negative correlations with the Kassarjian Social Character Scale measuring inner-directedness versus other-directedness). Furthermore, confirmatory factor analyses comparing a single-factor model against the hypothesized two-factor model consistently demonstrate that the two-factor model yields a significantly superior fit ($\Delta\chi^2$, p < .001), confirming that normative and informational dimensions represent distinct constructs rather than a singular general susceptibility factor.

Predictive and Nomological Validity

The scale possesses remarkable predictive validity regarding actual consumer behaviors. In empirical choice experiments, high normative scorers consistently exhibit higher willingness to pay for publicly consumed, highly visible luxury goods (e.g., designer apparel, automobiles, watches) than low normative scorers, whereas informational susceptibility strongly predicts consultation of expert consumer reports, online consumer review interaction, and reliance on peer recommendations when evaluating technically complex or high-risk goods.

8. Reliability

The CSII consistently demonstrates superior internal consistency and temporal stability across diverse populations and sampling frames.

Internal Consistency

In the original validation studies conducted by Bearden, Netemeyer, and Teel (1989), internal consistency metrics systematically exceeded established psychometric thresholds:

• Normative Influence Subscale (8 items): Cronbach’s alpha ($lpha$) estimates ranged from .88 to .92 across both collegiate and non-student adult samples. Construct reliability (composite reliability, CR) consistently surpassed .89.
• Informational Influence Subscale (4 items): Cronbach’s alpha ($lpha$) estimates ranged from .82 to .86 across independent cohorts. Composite reliability values consistently exceeded .83.
• Total CSII Scale (12 items): Overall instrument internal consistency generally registers between .88 and .93.

Subsequent cross-cultural validation studies (e.g., across French, German, Chinese, and Indian consumer segments) have routinely replicated these findings, with alpha values consistently maintaining levels well above .80 across translation conditions.

Test-Retest Reliability

To establish the temporal stability of the scale as an enduring individual-difference trait, Bearden et al. (1989) administered the CSII across a four-week interval to a test-retest sample. The resulting Pearson correlation coefficients were highly stable:

• Normative Subscale: $r = .79$ ($p < .001$)
• Informational Subscale: $r = .75$ ($p < .001$)
• Total CSII: $r = .81$ ($p < .001$)

These findings confirm that the CSII reflects a stable psychological orientation rather than transient mood states or momentary situational priming.

9. Factor Analysis

The dimensional structure of the CSII underwent exhaustive exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) during its development and subsequent structural evaluations.

Exploratory Factor Analysis (EFA)

Initial item pools containing over 50 preliminary items were subjected to common factor analysis with oblique (Promax) rotation, reflecting the theoretical expectation that normative and informational susceptibility correlate moderately. The EFA clearly delineated two primary eigenvalues exceeding unity. All eight normative items loaded heavily onto the primary factor (factor loadings ranging from .55 to .84), while showing negligible cross-loadings (typically < .20) on the secondary factor. Conversely, the four informational items loaded distinctively onto the second factor (loadings ranging from .62 to .86).

Confirmatory Factor Analysis (CFA)

Structural equation modeling via maximum likelihood estimation confirmed the theoretical two-factor oblique model across cross-validation samples. Goodness-of-fit statistics across classical validation cohorts demonstrated robust fit:

• Comparative Fit Index (CFI) values routinely exceed .93 (often exceeding .95 in homogeneous samples).
• Goodness-of-Fit Index (GFI) and Adjusted Goodness-of-Fit Index (AGFI) typically register above .92 and .89, respectively.
• Root Mean Square Error of Approximation (RMSEA) values generally fall between .045 and .068, falling well within acceptable cutoffs for good model fit.
• Inter-factor correlation ($phi$) between normative and informational latent factors typically ranges between .40 and .55, confirming that while the constructs share common variance as facets of interpersonal influence, they remain empirically distinguishable.

10. Instrument / Measurement Tool

The CSII is a brief, highly focused self-report questionnaire. Its structural parameters are summarized below:

• Instrument Name: Consumer Susceptibility to Interpersonal Influence (CSII)
• Authors: William O. Bearden, Richard G. Netemeyer, and Jesse E. Teel (1989)
• Target Population: General consumer populations (adolescents, young adults, and mature adults)
• Total Item Count: 12 items
• Subscales:
  • Normative Influence: 8 items (Items 2, 3, 5, 6, 8, 9, 10, 11)
  • Informational Influence: 4 items (Items 1, 4, 7, 12)
• Response Scale: 7-point Likert scale (1 = Strongly Disagree to 7 = Strongly Agree; often adapted to a 6-point scale without a neutral midpoint)
• Scoring Protocol:
  • All items are directly scored; no reverse-scored items are present.
  • Normative Subscale Score: Sum or arithmetic mean of items 2, 3, 5, 6, 8, 9, 10, and 11.
  • Informational Subscale Score: Sum or arithmetic mean of items 1, 4, 7, and 12.
  • Overall CSII Score: Sum or arithmetic mean of all 12 items.
  • Higher scores signify greater susceptibility to social influence.

11. Permissions & Fee and Test Year

The Consumer Susceptibility to Interpersonal Influence scale was published in 1989 in the Journal of Consumer Research. Under academic fair use conventions, the scale items are widely accessible for non-commercial educational, scientific, and scholarly empirical research without licensing fees, provided proper academic attribution is maintained.

Researchers intending to integrate the CSII into commercial market research tools, proprietary consulting platforms, or revenue-generating software systems should review terms governed by the publisher (Oxford University Press / Journal of Consumer Research, Inc.) or directly contact the primary authors.

12. References

• Bearden, W. O., Netemeyer, R. G., & Teel, J. E. (1989). Measurement of consumer susceptibility to interpersonal influence. Journal of Consumer Research, 15(4), 473–481. https://doi.org/10.1086/209186
• Coopersmith, S. (1967). The antecedents of self-esteem. W. H. Freeman.
• Deutsch, M., & Gerard, H. B. (1955). A study of normative and informational social influences upon individual judgment. The Journal of Abnormal and Social Psychology, 51(3), 629–636. https://doi.org/10.1037/h0046408
• Kelman, H. C. (1958). Compliance, identification, and internalization: Three processes of attitude change. Journal of Conflict Resolution, 2(1), 51–60. https://doi.org/10.1177/002200275800200106
• Kelman, H. C. (1961). Processes of opinion change. Public Opinion Quarterly, 25(1), 57–78. https://doi.org/10.1086/266996
• Lennox, R. D., & Wolfe, R. N. (1984). Revision of the Self-Monitoring Scale. Journal of Personality and Social Psychology, 46(6), 1349–1364. https://doi.org/10.1037/0022-3514.46.6.1349
• Park, C. W., & Lessig, V. P. (1977). Students and housewives: Differences in susceptibility to reference group influence. Journal of Consumer Research, 4(2), 102–110. https://doi.org/10.1086/208685
• Snyder, M. (1974). Self-monitoring of expressive behavior. Journal of Personality and Social Psychology, 30(4), 526–537. https://doi.org/10.1037/h0037039

13. Items of the Scale