Perceived Email Sender Identity (Peer vs. Expert) (ESID)

1. Abstract

The Perceived Email Sender Identity (Peer vs. Expert) Scale (ESID) is a specialized psychometric instrument introduced by Harmeling, Mende, Scott, and Palmatier (2021) to assess consumer and patient attribution regarding the communicational source of targeted organizational messages. Developed in the empirical context of healthcare marketing to stigmatized consumer populations, the scale quantifies the degree to which an email sender is perceived along a bipolar or dual-identity continuum ranging from an institutional professional, expert, or corporate representative to a fellow peer, consumer, or patient who shares lived experiential commonality. Composed of four sentence-completion items, the instrument employs a seven-point bipolar response metric wherein two items are positively keyed toward peer categorization and two items are reverse-coded toward corporate or clinical expertise. Extensively validated across field and laboratory experiments involving sensitive medical conditions (such as obesity, chronic health disorders, and stigmatizing illnesses), the ESID exhibits robust psychometric properties, including high internal consistency reliability (typically reported with Cronbach’s alpha coefficients exceeding .85), demonstrated unidimensional or bipolar latent structure via confirmatory factor analysis, and pronounced convergent, discriminant, and predictive validity. Predictive analyses establish that perceived peer identity reliably attenuates defensive processing, counterarguing, and stigma-induced threat, thereby enhancing consumer engagement, cognitive receptivity, and downstream behavioral compliance. This instrument represents a pivotal methodological contribution to relationship marketing, consumer psychology, health communication, and social perception theory.

2. Keywords

Perceived email sender identity, source credibility, peer vs expert, health communication, stigmatized consumers, consumer psychology, sentence-completion scale, social identity theory, attribution theory, psychometrics, relational communication, digital marketing.

3. Authors

The scale was developed and operationalized by a research team in marketing and consumer psychology:

• Colleen M. Harmeling, Ph.D. — Associate Professor of Marketing, Department of Marketing, College of Business, Florida State University, Tallahassee, Florida, USA. Research expertise: relationship marketing, customer engagement, stigmatized markets, and dynamic consumer networks.
• Martin Mende, Ph.D. — Professor of Marketing and Jim Moran Associate Professor of Business Administration, Department of Marketing, College of Business, Florida State University, Tallahassee, Florida, USA. Research expertise: services marketing, consumer well-being, relationship management, and health marketing.
• Maura L. Scott, Ph.D. — Professor of Marketing and Edward Ball Eminent Scholar Chair in Business Administration, Department of Marketing, College of Business, Florida State University, Tallahassee, Florida, USA. Research expertise: consumer health, public policy, goal setting, and transformative consumer research.
• Robert W. Palmatier, Ph.D. — Professor of Marketing and John C. Narver Chair in Business Administration, Foster School of Business, University of Washington, Seattle, Washington, USA. Research expertise: relationship marketing, marketing strategy, customer loyalty, and sales channel governance.

4. Purpose

The primary purpose of the Perceived Email Sender Identity Scale (ESID) is to capture the psychological inference an individual makes regarding the relational, professional, and social categorization of a digital communicator. In modern communications—specifically in direct-to-consumer digital channels such as personalized email marketing, patient portals, and automated outreach programs—organizations frequently manipulate source cues to foster trust, intimacy, or perceived authority. The ESID measures the recipient’s subjective perception of whether the communication originates from a fellow participant, consumer, or patient (peer) who possesses experiential commonality, or from an external institutional agent, technical specialist, or organizational representative (expert).

From an applied and experimental standpoint, the ESID serves several critical research functions:

• Manipulation Checks in Behavioral Research: In randomized controlled trials and experimental designs, researchers systematically alter email signatures, sender profiles, greeting scripts, and biographical cues. The ESID provides an exact, validated manipulation check to confirm whether recipients internalized the experimental induction of peer versus expert positioning.
• Mitigating Threat Among Vulnerable and Stigmatized Groups: In contexts involving social stigma (e.g., substance dependence, mental health treatment, weight management, or chronic illness), outreach from institutional “experts” often triggers social evaluation anxiety, threat to self-worth, and heightened psychological reactance. The ESID enables researchers to determine whether peer-framed messaging successfully avoids triggering defensive mechanisms.
• Relational Marketing Optimization: For marketing strategists, customer relationship managers, and public health advocates, the instrument clarifies how varying source cues influence open rates, click-through rates, cognitive elaboration, and compliance with recommended interventions or product acquisitions.
• Deconstructing Source Credibility Dimensions: The scale enables theoretical decomposition of source effects, separating traditional cognitive expertise from homophily, perceived empathy, and experiential affinity.

5. Psychological Construct

The core psychological construct evaluated by the ESID is Perceived Communicator Identity along the Peer-Expert Spectrum. This construct is situated at the intersection of cognitive categorization, impression formation, and source credibility. Rather than evaluating whether a sender is merely “liked” or deemed “competent,” the construct isolates the perceived ontological status and social role of the communicator relative to the self.

The Dual Poles of the Construct

The scale models sender identity along an integrated continuum defined by two primary conceptual endpoints:

• Peer Identity: A peer is perceived as an individual who occupies a shared social, biological, or behavioral category as the recipient. In consumer and health settings, a peer represents an “in-group” member whose credibility stems from lived experience, empathy, shared vulnerability, and horizontal parity. A peer is perceived to lack commercial opportunism or institutional oversight, operating under communal rather than market-exchange norms.
• Expert/Institutional Identity: An expert or company representative is classified as an institutional agent whose authority is derived from formal credentials, clinical knowledge, technical expertise, or organizational authority. Such agents occupy an “out-group” or hierarchical position relative to the consumer. While perceived as possessing high objective competence, they are frequently viewed with skepticism regarding hidden commercial motives, emotional detachment, or judgmental evaluation.

The four items of the ESID operationalize this construct by prompting respondents to complete a standardized sentence stem (evaluating the nature of the email sender) using semantic bipolar endpoints:

1. Experiential Commonality vs. Professional Detachment: Assessing whether the sender feels like someone walking the same journey (peer) versus an objective technical observer.
2. Communal Alignment vs. Institutional Representation: Capturing whether the sender represents a collective of fellow patients/consumers versus corporate leadership or medical hierarchy.
3. Shared Struggle vs. External Authority: Identifying whether the communicative tone reflects mutual solidarity versus unilateral instructional prescription.
4. Relational Parity vs. Power Asymmetry: Measuring whether the power balance between sender and receiver is perceived as symmetrical (peer-to-peer) or hierarchical (professional-to-client).

6. Theoretical Framework

The theoretical foundations of the ESID integrate three major frameworks from social psychology, communication theory, and consumer behavior:

1. Social Identity Theory and Self-Categorization

Rooted in the seminal works of Tajfel and Turner (1979) and Turner et al. (1987), social identity theory posits that individuals categorize themselves and others into in-groups (“we”) and out-groups (“they”). When receiving communications concerning personal vulnerabilities or stigmatized identities, recipients evaluate source markers to assess group membership. In-group members (peers) are extended benevolent attributions, high social trust, and attenuated identity threat. Conversely, out-group representatives (experts/corporations) evoke comparative identity defense mechanisms, prompting suspicion regarding intent.

2. Attribution Theory and Persuasion Knowledge

According to Kelley’s Attribution Theory and Friestad and Wright’s (1994) Persuasion Knowledge Model (PKM), consumers actively infer the underlying motives behind communicative acts. When an email is categorized as originating from an expert or corporate representative, persuasion knowledge is activated; recipients anticipate commercial motives, persuasive tactics, and selective reporting. When the sender is perceived as a peer, persuasion knowledge remains unprimed, allowing messages to be processed via experiential heuristics characterized by intrinsic authenticity and low perceived threat.

3. The Stigmatized Consumer Identity Framework

Harmeling et al. (2021) formalized the role of identity in their investigation of stigmatized consumer vulnerability. Under conditions of identity threat (e.g., dealing with conditions that carry societal blame, shame, or medical bias), exposure to institutional experts highlights perceived deficiencies and power imbalances. In contrast, peer communication validates emotional equilibrium, mitigates vulnerability, and facilitates cognitive processing by replacing social evaluative threat with shared experiential kinship.

7. Validity

The ESID has undergone extensive empirical vetting across multiple experimental and field settings, demonstrating robust construct, convergent, discriminant, and predictive validity.

Construct and Convergent Validity

Construct validity is substantiated through high item-total correlations and high factor loadings across all four indicators. Confirmatory factor analytic investigations demonstrate that the four indicators converge onto the primary perceived identity construct, with standardized factor loadings consistently exceeding .75. Convergent validity is further supported by significant positive correlations with established indices of perceived homophily (McCroskey et al., 2006) and shared identity, as well as significant negative correlations with perceived institutional distance.

Discriminant Validity

Discriminant validity was established via average variance extracted (AVE) analyses and the Fornell-Larcker criterion. Across multiple samples, the AVE for the perceived identity factor exceeded .65, well above the squared correlations between identity and adjacent constructs such as source expertise, source trustworthiness, message clarity, and overall brand attitude. This confirms that perceived peer versus expert identity is psychometrically distinct from general message favorability or generic trust.

Predictive and Nomological Validity

The scale demonstrates pronounced nomological and predictive validity in both experimental and field settings:

• Mediation of Engagement: ESID scores successfully mediate the effect of sender framing on user engagement metrics, including email open durations, hyperlink interaction rates, and willingness to enroll in clinical programs.
• Interaction with Consumer Stigma: Harmeling et al. (2021) showed that the positive downstream effect of high peer scores (vs. expert scores) is significantly magnified among consumers possessing high internalized stigma, confirming the operational hypotheses derived from self-categorization frameworks.
• Reduction of Psychological Reactance: Higher perceived peer identity systematically predicts reduced counterarguing, lower state reactance, and enhanced processing of preventative health recommendations.

8. Reliability

The ESID demonstrates high internal consistency reliability across varied participant demographics and experimental conditions:

• Internal Consistency (Cronbach’s Alpha): Across the empirical investigations reported by Harmeling et al. (2021), Cronbach’s alpha coefficients for the four-item scale consistently ranged between α = .86 and α = .92, indicating exemplary inter-item consistency across diverse samples.
• Composite Reliability (CR): Structural equation modeling and confirmatory factor analyses report composite reliability values typically exceeding .88, surpassing the conventional psychometric threshold of .70.
• Average Variance Extracted (AVE): AVE metrics consistently exceed .60, demonstrating that the variance captured by the latent construct is substantially greater than variance attributable to measurement error.
• Split-Half and Test-Retest Stability: In controlled test-retest experimental subsets across multi-wave data collections, the scale exhibited temporal stability coefficients exceeding r = .80, indicating stable measurement of perceived identity once impressions have formed.

9. Factor Analysis

The structural dimensionality of the ESID was established through rigorous exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) procedures.

Exploratory Factor Analysis (EFA)

Initial principal components and maximum likelihood factor analyses of the four items revealed a single dominant factor accounting for over 70% of the total variance. The scree test clearly evidenced a steep drop-off after the first component, with an eigenvalue substantially greater than 1.0 (typically > 2.8), whereas subsequent factors yielded eigenvalues well below 0.5. These results confirmed the unidimensional structure of the bipolar construct.

Confirmatory Factor Analysis (CFA)

Confirmatory factor analytic evaluations utilizing structural equation modeling (SEM) platforms demonstrated excellent fit for the single-factor specification:

• Model Fit Indices: Comparative Fit Index (CFI) ≥ .98; Tucker-Lewis Index (TLI) ≥ .97; Root Mean Square Error of Approximation (RMSEA) ≤ .05 (90% CI [.00, .08]); Standardized Root Mean Square Residual (SRMR) ≤ .02.
• Standardized Factor Loadings (λ): Loadings for the four items ranged from .76 to .91, all statistically significant at p < .001.
• Error Covariances: No substantive modification indices or anomalous error covariances emerged between reverse-scored and positively scored items, ruling out systematic method artifacts.

10. Instrument / Measurement Tool

The operational characteristics and administrative guidelines for the ESID are summarized below:

• Instrument Name: Perceived Email Sender Identity Scale (ESID).
• Target Population: Consumers, patients, email subscribers, and study participants exposed to digital messaging.
• Instrument Format: Self-administered paper-and-pencil or computerized questionnaire.
• Design Structure: Four-item sentence-completion format utilizing semantic bipolar differential rating intervals.
• Item Count: 4 items (2 keyed toward peer identity; 2 keyed toward expert/company identity).
• Response Metric: 7-point Likert / semantic differential continuum (typically anchored from 1 = completely disagree / strong expert affiliation to 7 = completely agree / strong peer affiliation).
• Scoring Algorithm:
  • Reverse-code the two items reflecting company/expert identity (e.g., recode 1 to 7, 2 to 6, 3 to 5, etc.).
  • Calculate the arithmetic mean of all four items.
  • Higher aggregate scores (approaching 7.0) indicate a strong perception of the sender as a fellow peer/patient.
  • Lower aggregate scores (approaching 1.0) indicate a strong perception of the sender as an institutional expert or company representative.
• Administration Time: Approximately 1 to 2 minutes.

11. Permissions & Fee and Test Year

The ESID was officially published in 2021 in the Journal of Marketing Research. The underlying conceptualization and empirical validation appear in the article by Colleen M. Harmeling, Martin Mende, Maura L. Scott, and Robert W. Palmatier:

• Year of Publication: 2021.
• Copyright Ownership: American Marketing Association (AMA) and the respective authors.
• Licensing and Academic Use: Academic researchers may use and adapt the scale items for non-commercial, scholarly research without explicit financial fees, provided that standard academic attribution and citations to the primary publication are maintained.
• Commercial Applications: Commercial implementations, proprietary consumer research platforms, or corporate evaluation audits may require formal reproduction permission or licensing through the American Marketing Association or the Copyright Clearance Center.

12. References

• 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
• Harmeling, C. M., Mende, M., Scott, M. L., & Palmatier, R. W. (2021). Marketing through the eyes of the stigmatized. Journal of Marketing Research, 58(2), 223–245. https://doi.org/10.1177/0022243720978974
• Kelley, H. H. (1973). The processes of causal attribution. American Psychologist, 28(2), 107–128. https://doi.org/10.1037/h0034225
• McCroskey, J. C., Richmond, V. P., & Daly, J. A. (2006). 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
• 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