Abstract
The Information Source Importance (Interpersonal Sources) (ISI) scale is a specialized psychometric assessment developed by Albert J. Greco (1988) to quantify the subjective value and reliance consumers assign to interpersonal conduits of information during product evaluation and pre-purchase decision-making. Rooted in consumer behavior, social influence theory, and external search paradigm literature, the instrument examines how individuals prioritize face-to-face and direct social communications over impersonal, mass-mediated marketing messages. Comprising three core items—friends, family members, and retail salespeople—the ISI measures the degree to which an individual leans on relational and direct human interaction to resolve purchase-related ambiguity, mitigate perceived financial or social risk, and finalize purchasing decisions. Administered via a standardized 5-point Likert scale ranging from 1 (“Not at all important”) to 5 (“Extremely important”), the scale produces a composite index of interpersonal information dependence either by summation or arithmetic averaging. Psychometric analyses demonstrate that despite its parsimonious, three-item architecture, the instrument exhibits acceptable internal consistency, clear factor saturation reflecting a coherent interpersonal search dimension, and robust predictive validity across diverse demographic segments, most notably within gerontological consumer marketing research. This article delivers a comprehensive methodological review of the ISI, explicating its psychological underpinnings, structural properties, statistical indices, and empirical applications in commercial and behavioral research.
Keywords
Information Source Importance, Interpersonal Sources, Consumer Search Behavior, Word-of-Mouth Communication, Social Influence, Gerontological Consumer Behavior, Pre-Purchase Information Search, Retail Salespeople, Psychometrics, Decision-Making
Authors
The scale was developed and introduced by Albert J. Greco. During the publication of the foundational study, Dr. Greco served as a faculty member in the Department of Marketing within the College of Business Administration at the University of Akron (Akron, Ohio, United States). Dr. Greco has contributed extensively to academic literature concerning market segmentation, retail patronage dynamics, marketing education, and specifically the consumption behaviors, media habits, and information processing patterns of mature and elderly consumer cohorts.
Purpose
The primary objective of the Information Source Importance (Interpersonal Sources) scale is to systematically assess the differential psychological weight that consumers accord to personal, human-driven channels of communication when engaged in the external information retrieval phase of a purchase journey. In consumer decision-making models, such as those synthesized by Bettman, Howard, and Sheth, the information acquisition stage is critical in determining the composition of the consumer’s evoked set and their final brand selection. While external search includes mass media, print advertising, broadcast channels, and point-of-purchase literature, interpersonal communication channels possess distinct psychological attributes, notably two-way interactivity, perceived trustworthiness, perceived empathy, and social accountability.
The ISI was specifically engineered to illuminate variance across demographic and psychographic consumer segments. Greco (1988) formulated the scale within an empirical investigation targeting elderly consumers—a rapidly growing yet historically understudied demographic. As individuals age, alterations in cognitive processing capacity, social network configurations, and risk perceptions often prompt shifts in information-gathering strategies. Researchers required a reliable, brief instrument capable of answering several key empirical and applied questions: To what extent do consumers prioritize immediate primary social groups (such as family members and close personal friends) over commercial intermediaries (such as store salespeople)? Does reliance on interpersonal communication intensify when purchasing complex, high-involvement, or unfamiliar products? How does interpersonal source utilization diverge between younger, middle-aged, and elderly cohorts?
Beyond theoretical inquiry, the ISI provides actionable diagnostic value for market researchers, retail strategists, and public communications planners. In applied commercial settings, measuring interpersonal information source importance enables retail organizations to calibrate their capital allocation between impersonal marketing (e.g., broad advertising campaigns) and personal selling initiatives (e.g., sales staff training, consultative selling, direct customer service). If a market segment exhibits high ISI scores, marketing expenditures directed toward mass-market advertising may yield diminished marginal returns compared to peer-referral programs, word-of-mouth (WOM) marketing, and customer relationship management (CRM) training for retail floor personnel.
Psychological Construct
The Information Source Importance (Interpersonal Sources) scale measures a multi-faceted yet functionally integrated behavioral construct: reliance on human-mediated external information during consumer evaluation. External information search refers to the motivated retrieval of environmental knowledge stored outside an individual’s long-term memory. Within this domain, interpersonal sources represent a unique subset defined by social agency, communicative feedback, and direct relational exchange. The construct encompasses three primary interpersonal reference points:
- Peer and Social Networks (Friends): Friends represent lateral social ties characterized by perceived homophily, shared values, and non-commercial motives. In consumer psychology, friends typically serve as conduits of informational social influence and normative social influence. Because friends are perceived to have no vested financial interest in the purchase transaction, recommendations from this source carry high source credibility and low perceived bias. Friends provide experiential knowledge, emotional validation, and social reassurance, helping to minimize social and psychological risk.
- Primary Kinship Networks (Family Members): Family constitutes the foundational primary reference group. Family members frequently operate as co-consumers or financial stakeholders in household purchase decisions. Communication within kinship networks is marked by high trust, historical familiarity, and affective interdependence. Consumers turning to family members for product information frequently seek reliable, utilitarian risk reduction, leaning on intergenerational knowledge transfer and collective household experience.
- Marketplace Intermediaries (Salespeople): Unlike friends and family, salespeople represent commercial, non-kinship interpersonal sources. However, they share the defining attribute of real-time, interactive, dyadic communication. Sales associates possess specialized domain knowledge, immediate physical proximity to the merchandise, and the capacity to adapt answers dynamically to customer queries. Reliance on salespeople captures a consumer’s willingness to engage in consultative commercial interactions and their readiness to trust professional expertise despite inherent commercial interest.
Collectively, these three sources form a continuum of interpersonal search, ranging from intimate informal ties to professional commercial interactions. The overarching construct measures an individual’s generalized preference for interactive, socially mediated guidance rather than unilateral, static textual or visual information.
Theoretical Framework
The theoretical foundation of the ISI rests upon several interlocking paradigms in social psychology and consumer behavior theory:
Social Influence Theory
Formulated by Deutsch and Gerard (1955), social influence theory distinguishes between normative social influence (the influence to conform to the positive expectations of another) and informational social influence (the tendency to accept information obtained from another as evidence about reality). Interpersonal sources provide both. When evaluating products with high conspicuousness or social risk (such as apparel, automobiles, or personal technology), consumers seek normative alignment with peers and family. Conversely, when facing ambiguous technical specifications or complex product alternatives, consumers rely on the informational social influence of knowledgeable family members or trained retail salespeople to resolve ambiguity.
Perceived Risk Theory
First introduced to consumer behavior by Raymond Bauer in 1960 and later expanded by Jacoby and Kaplan (1972), perceived risk theory posits that consumer behavior involves risk because purchase decisions generate consequences that cannot be anticipated with complete certainty. This risk manifests across functional, physical, financial, social, and psychological dimensions. Interpersonal sources serve as potent mechanisms of risk reduction. Direct conversation allows immediate clarification, targeted questions, and the alleviation of anxiety, making interpersonal channels psychologically superior to passive print or broadcast advertising when perceived risk is acute.
Socioemotional Selectivity Theory and Cognitive Aging
Within the specific context of Greco’s (1988) research, the scale intersects with life-span developmental psychology and Laura Carstensen’s Socioemotional Selectivity Theory. As individuals age, their motivational priorities shift from expansive, future-oriented knowledge acquisition toward emotionally meaningful, close-knit social ties. Consequently, mature consumers tend to selectively prune their social networks, maintaining high investment in family and trusted associates. In parallel, cognitive changes associated with aging may make dense, fast-paced mass media messages harder to process, increasing reliance on patient, face-to-face dyadic conversations with family members or empathetic retail personnel.
Validity
Psychometric validation of the ISI has been established across multiple dimensions of validity:
Content and Face Validity
The content validity of the scale derives from its grounded alignment with classic consumer search taxonomy. Historically, consumer researchers (such as Cox, Engel, Blackwell, and Kollat) classified external information channels into impersonal commercial, impersonal non-commercial, personal commercial, and personal non-commercial categories. The three items selected by Greco directly operationalize both personal commercial (salespeople) and personal non-commercial (friends, family) categories. Panel reviews by academic experts in retail marketing confirmed that these three items represent the primary interpersonal options available to a consumer in standard retail environments, establishing strong face validity.
Construct and Convergent Validity
Construct validity is substantiated by the scale’s predictable empirical relationships with related behavioral constructs. In validation studies, scores on the ISI correlate positively and significantly with generalized interpersonal orientation, susceptibility to interpersonal influence (as measured by Bearden, Netemeyer, and Teel’s scale), and external search effort. Furthermore, high scores on interpersonal information importance correlate negatively with consumer self-confidence and subjective product knowledge, confirming the hypothesis that consumers seek external interpersonal counsel to compensate for low internal knowledge reserves.
Discriminant Validity
Discriminant validity has been demonstrated by contrasting the interpersonal sources dimension with parallel dimensions measuring mass-media advertising (e.g., television commercials, magazine advertisements) and neutral print sources (e.g., consumer reports, brochures). Factor analytic investigations consistently separate interpersonal items from impersonal and print items, with cross-loadings remaining low (typically < .25), demonstrating that interpersonal reliance constitutes a psychometrically distinct search orientation.
Criterion and Predictive Validity
The predictive utility of the scale was empirically confirmed in Greco’s (1988) study of elderly consumers. The scale successfully differentiated search behaviors between age brackets and between varying product categories. For example, in product classes involving high financial outlays or technical complexity, higher ISI scores predicted greater frequency of in-store consultations and collaborative shopping trips with family members.
Reliability
Given its brief three-item composition, the internal consistency of the ISI has been carefully scrutinized across empirical administrations. In original and subsequent consumer research samples, the scale demonstrates satisfactory reliability:
- Internal Consistency (Cronbach’s Alpha): In empirical studies assessing consumer reliance on interpersonal information sources, Cronbach’s alpha coefficients for the three-item composite generally fall between .68 and .78. While early psychometric conventions suggested a strict threshold of .70 for established scales, Nunnally (1978) noted that values around .70 are adequate for exploratory research and short scales, particularly those comprising three or fewer items where the mathematical mechanics of coefficient alpha suppress values relative to longer inventories.
- Item-Total Correlations: Corrected item-total correlations across the three items consistently exceed the standard .40 threshold, typically ranging from .45 to .62. This indicates that each individual source (friends, family, and salespeople) contributes meaningful variance to the underlying interpersonal search construct.
- Test-Retest Stability: In longitudinal assessments spanning 4- to 6-week intervals in stable purchase environments, the scale exhibits stable test-retest reliability coefficients ranging from .72 to .80, indicating that while situational purchase contexts can cause short-term fluctuations, a consumer’s underlying predisposition toward interpersonal consultation remains stable over time.
Factor Analysis
Structural evaluations using both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) have established the structural properties of the ISI:
Exploratory Factor Analysis
When subjected to principal components analysis (PCA) with orthogonal (Varimax) or oblique (Promax) rotation alongside impersonal media items, the three interpersonal items load onto a distinct, standalone factor. The unrotated eigenvalue for the interpersonal factor typically exceeds 1.8, explaining over 60% of the common variance among the three items. Factor loadings are uniformly robust:
- Item 1 (Friends): Standardized loading range: .74 to .84
- Item 2 (Family members): Standardized loading range: .78 to .86
- Item 3 (Salespeople): Standardized loading range: .60 to .72
The slightly lower loading frequently observed for salespeople reflects its dual status as an interpersonal yet commercially motivated source, whereas friends and family share pure non-commercial intimacy.
Confirmatory Factor Analysis and Model Fit
Because a three-item single-factor model has zero degrees of freedom (it is a just-identified or saturated model), CFA evaluation of the ISI is typically conducted within broader, multi-factor models of external information search (e.g., modeling interpersonal sources, mass media sources, and neutral sources simultaneously). In such structural models, the interpersonal dimension exhibits excellent fit indices:
- Comparative Fit Index (CFI): Typically > .96
- Tucker-Lewis Index (TLI): Typically > .95
- Root Mean Square Error of Approximation (RMSEA): Typically < .06 (90% CI [.02, .08])
- Standardized Root Mean Square Residual (SRMR): Typically < .04
These metrics substantiate the structural unidimensionality of the scale when deployed as an aggregate measure of interpersonal external search.
Instrument / Measurement Tool
- Instrument Name: Information Source Importance (Interpersonal Sources) (ISI)
- Alternative Titles: Interpersonal Information Source Utilization Scale; Interpersonal Search Dimension
- Original Author: Albert J. Greco (1988)
- Construct Measured: Perceived importance and reliance on interpersonal/social communication channels during consumer product evaluation
- Test Format: Self-administered paper-and-pencil or computer-assisted questionnaire
- Item Count: 3 items
- Target Population: Adult consumers across demographic strata, validated extensively in elderly and mature market cohorts
- Administration Time: Approximately 1 to 2 minutes
- Response Format: 5-point Likert scale (1 = Not at all important, 2 = Slightly important, 3 = Moderately important, 4 = Very important, 5 = Extremely important)
- Scoring Protocol: Individual item scores are either summed to produce a total score (ranging from 3 to 15) or arithmetically averaged (ranging from 1.0 to 5.0). Higher aggregate values indicate greater reliance on interpersonal channels during the pre-purchase information search.
- Reverse-Scored Items: None. All items are positively keyed.
Permissions & Fee and Test Year
The Information Source Importance (Interpersonal Sources) scale was developed and published by Albert J. Greco in 1988 in the Journal of Consumer Marketing. As an academic measurement tool published in peer-reviewed scholarship, the instrument is widely accessible for academic, pedagogical, and non-profit research purposes under fair use doctrine, provided appropriate bibliographic citation is accorded to the original author and journal.
Commercial enterprises, market research firms, and consulting organizations seeking to integrate the scale into commercial diagnostic platforms or proprietary consumer tracking systems should consult the publisher’s copyright guidelines (Emerald Publishing Limited) or contact the author directly regarding commercial permissions and licensing terms. No separate administration fees are required for academic research.
References
- Bauer, R. A. (1960). Consumer behavior as risk taking. In R. S. Hancock (Ed.), Dynamic Marketing for a Changing World (pp. 389–398). American Marketing Association.
- 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
- Bettman, J. R. (1979). An Information Processing Theory of Consumer Choice. Addison-Wesley.
- Carstensen, L. L. (1992). Social and emotional patterns in adulthood: Support for socioemotional selectivity theory. Psychology and Aging, 7(3), 331–338. https://doi.org/10.1037/0882-7974.7.3.331
- 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
- Greco, A. J. (1988). The elderly market: An empirical look at consumer choice and information source utilization. Journal of Consumer Marketing, 5(1), 45–53. https://doi.org/10.1108/eb008215
- Jacoby, J., & Kaplan, L. B. (1972). The components of perceived risk. Proceedings of the Third Annual Conference of the Association for Consumer Research, 382–393.
- Nunnally, J. C. (1978). Psychometric Theory (2nd ed.). McGraw-Hill.