Persuasion Knowledge in the Marketplace: A Meta‐Analysis

Eisend, Martin; Tarrahi, Farid Article — Published Version Persuasion Knowledge in the Marketplace: A Meta‐ Analysis Journal of Consumer Psychology Provided in Cooperation with: John Wiley & Sons Suggested Citation: Eisend, Martin; Tarrahi, Farid (2021) : Persuasion Knowledge in the Marketplace: A Meta‐Analysis, Journal of Consumer Psychology, ISSN 1532-7663, Wiley, Hoboken, NJ, Vol. 32, Iss. 1, pp. 3-22, https://doi.org/10.1002/jcpy.1258 This Version is available at: https://hdl.handle.net/10419/284829 Standard-Nutzungsbedingungen: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden. Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen. 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If the documents have been made available under an Open Content Licence (especially Creative Commons Licences), you may exercise further usage rights as specified in the indicated licence. http://creativecommons.org/licenses/by-nc/4.0/ Persuasion Knowledge in the Marketplace: A Meta-Analysis Martin Eisend , and Farid Tarrahi European University Viadrina Accepted by Anirban Mukhopadhyay and Lauren Block, Editors; Associate Editor, Derek Rucker Since the introduction of the persuasion knowledge model more than 25 years ago, many research studies have investigated how consumers’persuasion knowledge affects their reactions to persuasion attempts. While most results have shown that persuasion knowledge increases coping responses and leads to less favorable evaluations of marketer actions, the findings vary considerably, leaving researchers with a limited understanding of the substance and structure of persuasion knowledge effects and the conditions that explain their variability. To develop a better understanding of persuasion knowledge effects in the marketplace, this study builds on the concept of persuasion to predict responses to marketers’attempts to persuade consumers with different levels of persuasion knowledge. The study presents a meta-analysis of the findings in 148 papers and 171 distinct data sets. Persuasion knowledge effects can be viewed as substantial compared with persuasion attempts, but persuasion knowledge cannot suppress or eliminate persuasion effects in the marketplace, as it only reaches around 50% of the explanatory power of persuasion. Persuasion knowledge effects on evaluations and coping depend on the characteristics of the persuasion process. All persuasion elements that help consumers identify and better understand benefits not just for themselves, but also for marketers and how marketers realize their benefits—such as the use of personal communication, communication about unfamiliar products or products with experience attributes, and receiver experience—lead to less favorable effects for marketers. This paper’s insights provide a new framework for persuasion knowledge effects in the marketplace, ideas for future research, and implications for researchers, consumers, policymakers, and marketers. Keywords Persuasion knowledge; Persuasion; Consumer; Meta-analysis Since the introduction of the persuasion knowledge model more than 25 years ago (Friestad & Wright, 1994), plenty of research studies have investigated how consumers develop persuasion knowledge (e.g., Nelson, 2016; Wright, Friestad, & Boush, 2005), when and how consumers use their persuasion knowledge (e.g., Boerman, Van Reijmersdaal, & Neijens, 2012; Campbell & Kirmani, 2000; Friestad & Wright, 1995), and how their persuasion knowledge affects their reactions to persuasion attempts (e.g., Isaac & Grayson, 2017; Panic, Cauberghe, & Pelsmacker, 2013). Insights about persuasion knowledge effects are of interest to researchers, marketers, consumers, and public policymakers because they carry major implications for marketing actions’effectiveness and consumers’susceptibility to these actions. However, most findings concerning persuasion knowledge effects vary considerably, leaving both researchers and practitioners with a limited understanding of persuasion knowledge effects’substance and structure, as well as the conditions that explain their variability. As for persuasion knowledge effects’substance and structure, research provides the general insight that persuasion knowledge increases consumers’ coping responses and leads to less favorable evaluations (Campbell & Kirmani, 2008), but it does not tell us how strong these effects are compared with the effects from persuasion in the marketplace: Are persuasion knowledge effects strong enough to reduce or even eliminate the influence from marketers’persuasion attempts? Unfortunately, prior research provides mixed findings on the direction, strength, and hierarchy of persuasion knowledge effects on different consumer responses. For example, the direction of persuasion knowledge effects on memory remains unknown (Cowley & Barron, 2008; Matthes, Schemer, & Wirth, 2007). Prior research also has found considerable variation in persuasion knowledge effects and indicates that under certain circumstances, persuasion knowledge Received 24 September 2019; accepted 6 June 2021 Available online 09 June 2021 This research received financial support from a research grant by the German Research Foundation (DFG: EI-508/10-1). Correspondence concerning this article should be addressed to Martin Eisend, Professor of Marketing, European University Viadrina, Grosse Scharrnstr. 59, Frankfurt 15230, Germany. Electronic mail may be sent to [email protected] ©2021 Society for Consumer Psychology All rights reserved. 1057-7408/2021/1532-7663/32(1)/3–22 DOI: 10.1002/jcpy.1258 can even lead to positive evaluations of persuasion agents (Isaac & Grayson, 2017; Kirmani & Campbell, 2004). How can the variation in persuasion knowledge effects on either coping or evaluation be explained, and under which conditions does persuasion knowledge lead to favorable or unfavorable results for marketers and consumers? In this study, we refer to the concept of persuasion to systematize consumer responses triggered by persuasion knowledge and to identify relevant moderators of persuasion knowledge effects. In doing so, we answered the above questions, which are important for a better and more comprehensive understanding of the concept of persuasion knowledge and its effects and, thus, its role and impact in the marketplace—insights that provide implications concerning persuasion knowledge for future research, as well as for consumers, public policymakers, and marketers. To this end, we metaanalyzed data provided in 148 prior research papers with 171 distinct data sets. Specifically, we compared persuasion knowledge effects’strength to the strength of persuasion effects in the marketplace and decided to what extent persuasion knowledge effects can reduce or even eliminate persuasion effects. We further resolved the ambiguities of effects in prior research and identified the direction, strength, and structure of the effects related to coping responses, evaluations, intentions and behavior, and memory and learning. Finally, we demonstrated that persuasion elements that help consumers identify and better understand persuasion attempts’benefits, not just for themselves, but also for marketers and how marketers realize their benefits—such as the use of personal communication, messages about unfamiliar products or products with experience and credence attributes, and receivers’experience—lead to less favorable effects for marketers. These findings inform marketers about conditions that jeopardize their investments’effectiveness, and they inform consumers about conditions when they are more susceptible to marketers’ persuasion attempts. They further provide a basis for future research ideas on persuasion knowledge. Theoretical Background Persuasion and Persuasion Knowledge Persuasion knowledge refers to consumers’ knowledge and beliefs regarding marketers’persuasion goals and attempts, as well as their underlying motives and tactics, and how persuasion works (Friestad & Wright, 1994). At the core of persuasion knowledge lies the concept of persuasion, and defining persuasion knowledge necessitates understanding what persuasion entails. Despite a multitude of definitions, conceptualizations, and persuasion models, the common idea of persuasion is that it is an intentional effort through communication to influence a receiver who has some degree of freedom of choice (e.g., O’Keefe, 2002; Perloff, 2017). This view is broader than equating persuasion with attitude change, which is a common approach by attitude researchers and focuses on a smaller set of consumer response variables than the present meta-analysis (Bohner & Dickel, 2011). Persuasion in the marketplace benefits not only the receiver, but also the sender and influencer, which is a common assumption in persuasion models, with the persuasion knowledge model suggesting that the influencer harbors ulterior and selfserving motives (Campbell & Kirmani, 2008; Friestad & Wright, 1994). With increasing persuasion knowledge, receivers’ability to recognize, reflect upon, understand, and evaluate influencers’intentions and efforts increases. Receivers with more persuasion knowledge can understand not only benefits for themselves, but also benefits for influencers and how influencers pursue their benefits. They compare these benefits, which influence persuasion attempts’outcomes. The definition of persuasion indicates that knowledge of persuasion can refer to and affect outcomes that are either intended or unintended by the influencer. Influencers’intended outcomes in a marketing context refer to brand-, channel-, and companyrelated evaluations, intentions, behavior, and memories of consumers. If consumers gain insights into persuasion that benefit not only the consumer, but also the marketer, and if they see that marketers use potentially manipulative techniques, and might even intend to reduce consumers’choices (e.g., through building brand loyalty), they develop coping responses, as suggested by reactance theory (Brehm, 1966). These coping responses are outcomes that are not intended by the marketer. The conceptual framework in Figure 1 depicts both types of outcomes, which are described and explained in more in Table 1. Persuasion knowledge effects on outcome variables vary. Prior research has shown that increasing persuasion knowledge not only makes consumers more critical of persuasion and develops reactance, but also may improve consumers’skills in identifying benefits for themselves from marketers’persuasion attempts. Thus, they might even develop more favorable evaluations with increasing persuasion 4 Eisend and Tarrahi knowledge (Isaac & Grayson, 2017). Whether and how consumers activate and apply their persuasion knowledge and how it affects their reactions depend on the cues that persuasion attempts provide to consumers. Because persuasion is a communication phenomenon, we can systematize the cues in line with the major elements of the communication or persuasion process (Lasswell, 1948): source; message; channel; and receiver. For instance, if a source lacks transparency, consumers with more persuasion knowledge are more likely to assume a hidden and ulterior motive that reduces the perception of their benefits compared with the marketer’s benefits, leading to more source-unfavorable outcomes than with a transparent source. Figure 1 depicts persuasion process moderators besides methodological and other moderators that we consider in our meta-analysis. Note that the different types of knowledge, such as agent or topic knowledge, that have been suggested by Friestadt and Wright (1994) correspond to communication elements, but do not include channel or receiver characteristics as potential moderators of persuasion knowledge effects. To provide a complete picture of persuasion knowledge research, Figure 1 further depicts the main antecedents of persuasion knowledge as investigated in prior research, although they are not empirically addressed in this meta-analysis. Most research has focused either on individual factors that influence persuasion knowledge development or on contextual triggers that make marketers’ulterior motives accessible, such as sponsorship disclosures. Individual factors refer to variations in expertise and cognitive resources, and as a variable related to both factors, age is the most-ofteninvestigated individual variable. The findings indicate that persuasion knowledge starts developing in childhood, starting at age 5; increases with age; and reaches a saturation level at senior age (Nelson, 2016; Rozendaal, Buijzen, & Valkenburg, 2011; Van Reijmersdaal, Rozendaal, & Buijzen, 2012). Contextual triggers also can induce cognitive resources’ availability (e.g., by distracting consumers; Campbell & Kirmani, 2000) and ulterior motives’accessibility. While many different triggers exist that provide information about marketers’motives, such as information about a firm’s business status or tactics (e.g., Brown & Krishna, 2004; Campbell & Kirmani, 2000; Morales, 2005), sponsorship disclosures that are relevant from both a managerial and public policy perspective have been investigated most intensively (e.g., Boerman & Van Reijmersdal, 2016; Eisend, Reijmersdal, Boerman, & Tarrahi, 2020). Sponsorship disclosures can activate and increase consumers’persuasion knowledge. Figure 1 provides an overview of prior persuasion knowledge research and depicts the conceptual framework for this meta-analysis that pertains to research in the gray area. Figure 1. Research on persuasion knowledge: overview and conceptual framework. Persuasion Knowledge Meta-Analysis 5 The Substance and Structure of Persuasion Knowledge Effects Persuasion knowledge leads to outcomes intended by the influencer (herein, marketerintended outcomes) that are investigated in most marketing communication and persuasion studies, as well as unintended outcomes, which are usually not investigated in this research stream. Similarly, Campbell and Kirmani (2008) distinguished between coping responses that occur during a persuasion episode and terminal outcomes related to evaluations, intentions, and behaviors. Coping responses comprise all cognitive, emotional, or behavioral efforts by consumers in dealing with and managing persuasion attempts, including cognitions, feelings, suspicions, or avoidance. Evaluations relate to the assessment of a persuasion object’s value, merit, or benefit, including variables such as brand attitudes, ad attitudes, or company evaluations. Table 1 depicts the outcomes that have been investigated commonly in prior persuasion knowledge research and, thus, are selected for and included in the meta-analysis. While some authors have included credibility, trustworthiness, or dislike measures as indicators of persuasion knowledge activation or as evaluative dimensions of persuasion knowledge (e.g., Boerman et al., 2012; Rozendaal, Slot, Van Reijmersdal, & Buijzen, 2013), most prior studies have emphasized the cognitive view Table 1 Persuasion Knowledge Effects on Consumer Response Variables Consumer response variable Definition Expected effect Marketer intended effects Evaluations Attitude toward the ad Evaluation of the ad and the advertised message Negative Attitude toward the brand Evaluation of the sponsored brand Company evaluation Evaluation of the sponsoring company and its representatives Media evaluation Evaluation of the media or platform that transmits the sponsored content Satisfaction Evaluation of purchasing outcomes compared with expectations Intentions and behavior Behavioral intention Consumers’likelihood of engaging in brand-favoring behavior or in the behavior advised in the ad message Negative Choice and behavior Consumers’brand-favoring choice and behavior or their actual choice and behavior in line with advice given in the ad message Memory and learning Brand recall Consumers’ability to retrieve a brand (name) from memory correctly when prompted by a product category ? Brand recognition Consumers’ability to correct their discernment of a brand as having been seen or heard before Learning Consumers’elaboration and knowledge acquisition Other positive responses Credibility The extent to which the source or message can be believed or trusted Negative Positive cognitions Cognitive responses of positive valence Positive feelings Emotional reactions of positive valence Marketer unintended effects Negative coping responses Avoidance Actions taken to avoid and reduce persuasive influences Positive Disapproval Disapproving evaluations and views of persuasion attempts Negative cognitions Cognitive responses of negative valence Negative feelings Emotional reactions of negative valence Suspicion Consumers’critical stance toward and processing of persuasion attempts and sources, expressed by suspicion and skepticism Other Price estimate Estimate of consumers’accepted price and/or sellers’price advantage ? Third-person perceptions Perceived influence on self (compared with others) 6 Eisend and Tarrahi suggested by Friestadt and Wright’s (1994) definition and have viewed evaluative constructs and coping responses as persuasion knowledge outcomes (Ham, Nelson, & Das, 2015) besides learning and memory and intentions and behavior. In this study, we follow the majority view of empirical studies. The outcomes in Table 1 are organized as evaluations, intentions and behavior, memory and learning, other positive responses, negative coping responses, and other variables, following the classifications from other meta-analyses dealing with persuasion effects (e.g., Eisend & Tarrahi, 2016). Although the outcomes are assumed to be related (e.g., strongly negative coping responses lead to less positive evaluations), the present meta-analysis— similar to other meta-analyses—investigates persuasion knowledge’s effects on each of the outcomes separately and independently. Considering that marketers are assumed to have self-serving ulterior motives that they often hide–– and persuasion knowledge increases the likelihood that consumers not only understand the benefits for themselves, but also recognize and understand marketers’motives––persuasion knowledge increases the likelihood of negative coping responses to allow consumers to control unwanted persuasive influences, leading to negative evaluations, intentions, and behaviors (e.g., Fransen, Verlegh, Kirmani, & Smit, 2015). While these effects have been well established in the literature, we do not know how these effects are manifested compared with marketer-intended and successful persuasion effects, such as positive brand attitudes. In particular, we do not know to what extent persuasion knowledge can reduce or even eliminate marketers’ intended persuasive influence. If persuasion knowledge, indeed, can reduce persuasion effects by a considerable amount or even eliminate them, then persuasion knowledge effects will be viewed as substantial and important. Aside from this major question regarding the substance of persuasion knowledge effects, several other open questions about the hierarchy and direction of responses triggered by persuasion knowledge can be answered through our meta-analysis. First, although the persuasion knowledge model is about knowledge, rather than emotions (Friestad & Wright, 1994), the coping responses can refer to consumers’cognitive, emotional, or behavioral efforts in dealing with and managing persuasion attempts. Although it is important for marketers, consumers, and public policymakers to understand what kind of responses they are dealing with to optimize their efforts to channel these responses in meaningful ways, we do not know whether the responses to persuasion knowledge are primarily emotional, cognitive, or behavioral. Regarding this, we do not know whether persuasion knowledge might sometimes lead to positive emotions, as it might be possible that people feel elation after successfully activating persuasion knowledge (Campbell & Kirmani, 2008). Second, persuasion knowledge mostly leads to negative evaluations, but it is unclear whether it affects all evaluation objects (e.g., company, brand, ads) in the same way. Conceptually, persuasion knowledge includes knowledge related to the persuasion process, including source and message elements; thus, the evaluation can affect various evaluation objects (Friestad & Wright, 1994). An intriguing question is whether consumers who activate persuasion knowledge evaluate the source as the party responsible for the persuasion attempt more negatively than other communication objects. The answer can provide insights to help marketers respond better to negative consumer responses due to persuasion knowledge. Third, researchers have begun to ask whether persuasion knowledge can exert positive effects (e.g., Campbell & Kirmani, 2008; Isaac & Grayson, 2017). An interesting outcome in this regard is consumers’memory and learning persuasion-related cues, which have led to ambiguous findings in prior research (e.g., Cowley & Barron, 2008; Matthes et al., 2007). Similar to other responses, any brand-favoring outcomes should be reduced; thus, persuasion knowledge should affect memory and learning negatively. However, knowledge and memory are not necessarily correlated (DeMarieDreblow, 1991), which also could imply a nonexistent relationship between persuasion knowledge and memory and learning. Explaining Variations in Persuasion Knowledge Effects Whether and how consumers apply their persuasion knowledge and how it affects their responses depend on cues that the persuasion attempt and situation provide to consumers, who, based on these cues, can identify the persuasion attempt’s benefits for themselves and for the marketers, compare and interpret these benefits, then react accordingly. The general idea is that with little or no persuasion knowledge, consumers mainly will identify benefits for themselves, as they are salient and easy to process and understand in the context of a persuasion attempt. For instance, most brand ads clearly Persuasion Knowledge Meta-Analysis 7 communicate brands’main benefits to consumers (e.g., a comfortable car, a healthy drink) (Bruce, Becker, & Reinartz, 2020). Even if benefits are subjective, persuasion in the marketplace commonly provides some benefits for the consumer, leading to positive evaluations by the consumer. However, with increasing persuasion knowledge, consumers can see beyond the persuasion attempt’s salient elements and recognize, process, and interpret other information about the persuasion process, marketers, and the persuasion context to reveal information about the benefits for the marketer and how marketers try to achieve these benefits through, for instance, manipulative tactics (Friestad & Wright, 1994). By better understanding the benefits for both consumers and marketers, consumers can compare their benefits to marketers’benefits and put their benefits into perspective, which can lead to more coping and less positive evaluations. By understanding that marketers tend to hide their intentions or sometimes use manipulative tactics, consumers take a more critical stance. Specific cues can help consumers with more persuasion knowledge better understand the benefits for both themselves and marketers, as well as how marketers try to realize their benefits. We systematize the cues in line with major elements of the communication or persuasion process (e.g., Lasswell, 1948): source; message; channel; and receiver. The persuasion process elements are moderators of persuasion knowledge effects. Next to these persuasion process elements, persuasion knowledge measures are also important moderators, as several items from these measures are related to the perception of marketers’persuasive intentions (Williams, Fitzsimons, & Block, 2004). Note that the variables that we ultimately have used to test persuasion process elements’moderating effects also are driven by methodological considerations and the availability of information provided in the primary studies included in the meta-analysis. As is common with a meta-analysis, all hypotheses are predictions using an “all else equal”approach and cannot consider conditional effects and moderators that are not provided in the primary studies included in the meta-analysis. Source A source characteristic that is likely to moderate persuasion knowledge effects is source transparency. Covert marketing (e.g., product placements in movies, blogger sponsoring, and native advertising) is not transparent concerning the source and its intentions, and the commercial source cannot be identified easily (Campbell, Mohr, & Verlegh, 2013; Wei, Fischer, & Main, 2008). With less persuasion knowledge, consumers are less likely to recognize covert marketing sources’ulterior motives. Instead, consumers focus on the benefits for themselves provided in the persuasive message, while with more persuasion knowledge, consumers can identify the source, its intentions, and applied tactics. Consumers can recognize marketers’benefits and put their own benefits into perspective, thereby developing more coping responses and less favorable evaluations. Note that our hypotheses are tested through a meta-analysis by assessing effect sizes. A stronger effect indicates a larger absolute value of an effect size, thereby indicating more positive effects on negative coping, but more negative effects on evaluations, and vice versa for weaker effects that are assessed by smaller effect sizes: H1: The effect of persuasion knowledge on evaluations and coping is stronger for covert sources vs. noncovert sources. Similar arguments have referred to personalized persuasive communication in the marketplace. With increasing persuasion knowledge, consumers are more likely to identify the marketer’s aims and benefits,aswellastheunderlyingtacticsinusingpersonalized communication over nonpersonalized communication. Understanding marketers’application of personalized communication can increase privacy concerns and reactance, which can lead to negative effects from personalized marketing communication (Aguirre, Mahr, Grewal, Ruyter, & Wetzels, 2015; Bleier & Eisenbeiss, 2015). As a result, greater persuasion knowledge leads to more coping and less favorable evaluations when personalization is high. H2: The effect of persuasion knowledge on evaluations and coping is stronger for personal sources vs. nonpersonal sources. Message The marketing communication message is created around a product. Messages for lowinvolvement products apply basic persuasion techniques, such as the application of sex appeals or humor; provide basic information about benefits for consumers; and lead to shallower processing (Rossiter, Percy, & Donovan, 1991). While consumers 8 Eisend and Tarrahi with less persuasion knowledge mainly will focus on salient benefits for themselves, consumers with greater persuasion knowledge are more likely to identify marketers’ulterior motives and see beyond basic persuasion techniques applied in messages for low-involvement products. Messages for highinvolvement products provide more detailed information and are processed more intensively. Thus, persuasion knowledge effects should be weaker, as all consumers are more likely to identify both benefits for themselves and benefits for marketers in messages for high-involvement products that are processed more thoroughly. H3: The effect of persuasion knowledge on evaluations and coping is stronger for low-involvement products vs. high-involvement products. Similar arguments refer to unfamiliar products in which consumers with less persuasion knowledge lack knowledge and information, and focus on the benefits for themselves, while consumers with more persuasion knowledge are better able to identify marketers’ulterior motives concerning unfamiliar products’persuasion attempts. As a result, they dismiss questionable or exaggerated information from unfamiliar products (Lee, 2014). In contrast, familiar products often are associated with high credibility regarding both the brand and the message (Hann & Berkey, 2002) and, thus, are less likely to trigger suspicion and ulterior motives among consumers, which should lead to an attenuation of persuasion knowledge effects: H4: The effect of persuasion knowledge on evaluations and coping is stronger for unfamiliar products vs. familiar products. Similar to messages for unfamiliar products, messages about intangible products, such as services (compared with goods) or products with primarily experience and credence attributes (e.g., organic fruits), rather than search attributes, are more difficult to evaluate (Weathers, Sharma, & Wood, 2007). Consumers with less persuasion knowledge lack knowledge and information, and focus on the benefits for themselves that are salient in the message, while consumers with more persuasion knowledge are more likely to identify marketers’ulterior motives and manipulative efforts with persuasion attempts. Products with search attributes, as well as goods and their benefits for both consumers and marketers, are easier to evaluate and, thus, the difference in persuasion knowledge effects should be lower. H5: The effect of persuasion knowledge on evaluations and coping is stronger for services vs. goods. H6: The effect of persuasion knowledge on evaluations and coping is stronger for products with experience or credence attributes vs. products with search attributes. Channel Consumers also make judgments about persuasive communication and media types based on their persuasion knowledge; they show more skepticism toward new media channels and perceive them as less credible compared with traditional ones (Moore & Rodgers, 2005). Persuasive communication in digital media, such as digital advertising, allows for many variations, is less regulated than traditional advertising, and is, therefore, more likely to lead to more suspicion and negative evaluations, such as the perception of privacy intrusion (Tucker, 2014). With increasing persuasion knowledge, consumers should be more aware of the differences between the use of online and offline channels in persuasion attempts; therefore, the difference in responses between both channels should increase. H7: The effect of persuasion knowledge on evaluations and coping is stronger for online channels vs. offline channels. Receiver Persuasion knowledge gradually develops throughout life, evolving from simple to more sophisticated knowledge and beliefs about persuasion (Friestad & Wright, 1994; Wright et al., 2005), that is, children and adolescents’persuasion knowledge is less developed than that of adults (Hudders et al., 2017). Therefore, children and adolescents are less likely to understand marketers’ulterior motives and manipulative actions, as their reactions are weaker, they show fewer coping responses, and their evaluations are more favorable: H8: The effect of persuasion knowledge on evaluations and coping is stronger for adult samples vs. samples with children and/or adolescents. Beyond the gradual development of persuasion knowledge throughout life, persuasion knowledge can increase significantly through education (Nelson, 2016; Wright, 2002). The more educated Persuasion Knowledge Meta-Analysis 9 someone is, the higher their media and advertising literacy and, thus, the higher their persuasion knowledge. Thus, in our meta-analysis, we distinguished between studies with student samples and nonstudent samples. Student samples comprised better-educated individuals than nonstudent samples. Therefore, they were more likely to have more persuasion knowledge, which leads to more negative coping responses and evaluations. H9: The effect of persuasion knowledge on evaluations and coping is stronger for samples with students vs. nonstudent samples. The development of persuasion knowledge also is influenced by how much practice consumers get during persuasion episodes and how much experience they gain from encountering persuasion situations (Friestad & Wright, 1994). The prevalent and intensive use of marketing in society provides several information sources, such as mass media commentary on marketing activities and advertising and sales expertise shared by marketing professionals in the media, which can increase consumers’persuasion knowledge and lead to corresponding outcomes (Friestad & Wright, 1994). However, there are two reasons why high-intensity marketing does not necessarily increase persuasion knowledge effects. First, persuasion knowledge might reach a ceiling in high-intensity marketing contexts. Second, research on competitive interference has provided strong evidence that increasing advertising clutter can even reduce memory and learning (Keller, 1991; Kent & Allen, 1994). Therefore, contexts with intensive marketer actions that create more clutter can even reduce persuasion knowledge’s effectiveness because consumers are less likely to identify marketers’ulterior motives and manipulative actions and, thus, simply focus on their own benefits. The U.S. has the highest marketing spending per capita (and, thus, the highest probability of advertising clutter) among the sample of countries in this meta-analysis, which includes several European countries and others with comparatively low marketing spending per capita, such as India, China, Iran, and Thailand. H10: The effect of persuasion knowledge on evaluations and coping is stronger in non-US samples vs. US samples. Measures In prior studies, persuasion knowledge has been measured by either dispositional/chronic or situational measures (Bri˜ nol, Rucker, & Petty, 2015; Ham et al., 2015). Chronic measures include knowledge of persuasion tactics (Boush, Friestad, & Rose, 1994), laypeople’s persuasion knowledge (Friestad & Wright, 1995), self-confidence in relation to persuasion knowledge (Bearden, Hardesty, & Rose, 2001), and pricing tactic persuasion knowledge (Hardesty, Bearden, & Carlson, 2007). Situational measures include ratings of persuasion-related beliefs (Campbell & Kirmani, 2008), encompassing scales that measure the inference of manipulative content (e.g., Campbell, 1995) or the understanding of persuasive intent and motives (e.g., Tutai & Van Reijmersdal, 2012). A chronic measure indicates general persuasion knowledge, but does not refer to a specific persuasion attempt or situation, while a situational measure refers to the particular persuasive communication attempt or situation. Other than a chronic measure, a situational measure captures persuasion knowledge that allows consumers to use cues concerning persuasion from the specific persuasion context. Thus, a situational measure is more specific and likely to better explain the variance in responses (both negative coping responses and evaluations), that is, it leads to stronger responses compared with a chronic measure. Situational measures, but not chronic ones, often are used in studies with experimental manipulations, and because experimental manipulations lead to stronger effects (e.g., Crosno & Dahlstrom, 2008; Geyskens, Steenkamp, & Kumar, 1998), this further underlines the assumption that effects should be stronger for situational, compared with chronic, persuasion knowledge. H11: The effect of persuasion knowledge on evaluations and coping is stronger for situational measures vs. chronic measures. Research on the development of persuasion knowledge in children distinguishes further between measures that reflect the different stages of persuasion knowledge development (Hudders et al., 2017; Nelson, 2016; Rozendaal et al., 2013; Wright et al., 2005). These measures refer to the recognition of persuasive communication and the recognition of the persuasion source, as well as the understanding of persuasive intent, both of which are commonly used measures in the persuasion knowledge literature. They will be considered in this meta-analysis, along with general persuasion knowledge measures that encompass both recognition and understanding of intent. The recognition of advertising is the first stage of persuasion knowledge development. Even if consumers recognize 10 Eisend and Tarrahi premise that increasing persuasion knowledge leads to effects that are generally unfavorable for marketers. Most of the effect sizes of persuasion knowledge’sinfluence were small to moderate, but the question remains as to how strong they are when compared with persuasion in the marketplace. If persuasion knowledge, indeed, can reduce or even eliminate persuasion effects, it is considered substantial and important. To answer the question, we compared the effects in this meta-analysis to persuasion effects as provided by a meta-meta-analysis of the effect sizes in advertising (Eisend & Tarrahi, 2016). As a caveat, it should be noted that a comparison of persuasion knowledge effects with advertising effects and the suggested explanations assume that persuasion knowledge is exogenous. However, persuasion knowledge might be endogenous and related to advertising intensity, that is, more advertising might increase persuasion knowledge, as consumers can gain experience and practice from encountering persuasion situations (Friestad & Wright, 1994). The sizes of persuasion knowledge effects on evaluations (−.098) or intentions and behavior (−.122) were significantly smaller than advertising’s general effects on attitudes (.214) or behavior (.199). Comparing persuasion knowledge effects’explanatory power with that of advertising effectiveness showed that persuasion knowledge effects reached around 50% of advertising’s explanatory power over consumer responses. This implies that these effects can be viewed as substantial because they can counteract and reduce advertising influences on consumers’evaluations and behaviors considerably, by 50%. Additionally, the findings indicated that persuasion knowledge is a factor that can contribute to and partially explain lesser advertising effectiveness, which has attracted substantial attention in the literature (e.g., Dahl´ en & Rosengren, 2016). The literature has discussed several explanations as to why marketing communication efforts go awry and advertising fails, for example, inattention, miscomprehension, or ineffective actions on the part of advertisers (e.g., overadvertising or lack of field tests and tracking; Tellis, 2004). However, the literature has neglected persuasion knowledge as an explanation. Our findings show that the development of persuasion knowledge generally does not imply that consumers fully control (i.e., by 100%) advertising’sinfluence, suggesting that despite developing persuasion knowledge, consumers cannot fully understand all the details of persuasion tactics and interpret how exactly persuasion works in the marketplace. These insights should encourage public policymakers to act to further increase consumers’persuasion knowledge or focus on alternative measures that can restrict consumers’susceptibility to marketing actions, such as regulations. The 50% figure in this meta-analysis can provide a benchmark for assessing persuasion knowledge’s capacity to handle persuasion in the marketplace. Explaining Variations in Persuasion Knowledge Effects on Coping and Evaluations While the literature suggests that persuasion knowledge positively affects coping and negatively affects evaluations, the variation in effects is considerable. Some studies even have shown that under certain conditions, consumers who cope successfully can better comprehend and carve out their benefits from a persuasion attempt, leading to positive evaluations via persuasion knowledge (Isaac & Grayson, 2017). Whether and how consumers apply their persuasion knowledge to identify persuasion benefits and their effects depend on the cues that persuasion process elements provide and that can help consumers identify marketers’ulterior motives and manipulative actions. Except for channel characteristics, we found significant moderating effects in the source, message, receiver characteristics, and measures of persuasion knowledge. Every time these elements helped consumers understand the benefits for both themselves and for marketers, and helped identify hidden ulterior motives and persuasion tactics as manipulative, persuasion knowledge effects became unfavorable for marketers, weakening their intended effects (here: evaluations) and strengthening unintended effects (here: negative coping). Figure 2 provides an overview of persuasion elements that explained variations in persuasion knowledge effects. The figure summarizes which kinds of sources, messages, receivers, and measures moderated persuasion knowledge effects. Persuasion processes with sources not deemed transparent nor obtrusive, messages that make only consumer benefits salient, experienced recipients, and specific persuasion knowledge measures increase persuasion knowledge effects that were unfavorable for marketers. Some of the moderators even revealed conditions under which persuasion knowledge did not harm marketers, but might have led to outcomes that were favorable for marketers. We found that negative persuasion knowledge effects on evaluations disappeared for children Persuasion Knowledge Meta-Analysis 17 or adolescents, and even became positive when persuasion knowledge measures were chronic. These findings carry several implications. Concerning consumers and public policy, persuasion knowledge effects can be activated or improved in such a way that they support consumers by increasing receiver expertise, providing information on sources’obtrusiveness or lack of transparency, or discounting messages as beneficial only for consumers. As for researchers, the results regarding persuasion knowledge measures show that persuasion knowledge research findings cannot be compared unless identical measures are used. Comparisons across studies with different measures are misleading. These insights also relate to marketers, who need to understand what kind of consumer persuasion knowledge they are dealing with to predict what kind of outcomes from their persuasion attempts they can expect. Because persuasion knowledge, on average, can decrease persuasion effects by 50%, conditions in which persuasion knowledge effects become even more unfavorable for marketers (e.g., messages for unfamiliar products or products with experience and credence attributes, as well as personalized communication) can jeopardize marketing investments in persuasion attempts considerably. A solution for marketers is to adopt their marketing communication practices to consumers with different degrees of persuasion knowledge. For instance, they should avoid personalization when communicating with consumers who possess much persuasion knowledge. Future Research While a meta-analysis should not be viewed as a substitute for new primary research (Cooper & Hedges, 1994), it can help ensure that the next wave of primary research is headed in the most illuminating research direction by identifying unsolved research problems and less-researched, but important, effects, and by suggesting factors that explain variations in effects. In this spirit, we suggest some areas that would benefit from further investigation. First, by explaining variations in effects, this meta-analysis used communication process cues that could be retrieved from primary studies and from which sufficient and specific data were available. Further moderators relating to the communication process elements could be considered in future primary research. The idea is that some communication elements help consumers develop more or less critical reactions, which influence whether they can identify the persuasion attempt’s benefits for both the consumer and marketer, as well as compare and evaluate these benefits. As for sources, endorsers and their fit with a product or endorser authenticity have not been investigated sufficiently as a cue that could increase or decrease critical thinking. Persuasion knowledge effects barely have been investigated, as they relate to message elements used commonly in advertising, such as humor, sex appeal, and creativity. These elements might be able to change the likelihood of critical thinking, for example, humor decreasing Figure 2. Explaining the variation in persuasion knowledge effects: a persuasion process perspective. 18 Eisend and Tarrahi critical thinking (Attardo, 1994). While the metaanalysis does not indicate differences between online and offline sources, comparisons of particular sources (e.g., TV vs. newspapers, banner ads vs. social media advertising) might be more informative, as they may trigger different degrees of critical thinking. As for receivers, the meta-analysis provides some intriguing differences that could be extended to consumers’other characteristics, such as gender or education, which can moderate the likelihood of critical thinking. Second, the meta-analysis relied on a cognitive view of persuasion knowledge and distinguished between chronic and situational measures. The differences in effects between different persuasion knowledge measures indicate that researchers need to be careful and clearly distinguish between persuasion knowledge concepts in which they are interested. Distinguishing between chronic and situational persuasion knowledge at the operational level –as well as between recognition, the understanding of intent, and general persuasion knowledge –can provide the first steps in developing more general persuasion knowledge measures (Boerman, Van Reijmersdal, Rozendaal, & Dima, 2017). Considering that persuasion is a dynamic phenomenon and that persuasion applications and methods change over time, the concept and measures of persuasion knowledge should be understood as dynamic, too. More than 25 years of persuasion knowledge research have shown that it is difficult to develop a generalizable and stable measure of persuasion knowledge. We might better understand persuasion knowledge as a dynamic concept that requires continuous and systematic monitoring and development (see Bergkvist & Eisend, 2021). Third, while the meta-analysis provided a framework encompassing antecedents and consequences of persuasion knowledge, it empirically summarized the consequences. A recent meta-analysis has examined disclosures’effects on persuasion knowledge (Eisend et al., 2020), but the effects from the second major antecedent variable, consumer age, have not been analyzed systematically. While we know that children have developed less persuasion knowledge than adults, we do not know whether the relationship between persuasion knowledge and age reaches a ceiling or follows a curvilinear relationship, and how the strength of this relationship depends on context factors, such as cultural differences in education or media consumption. Related to this, another important, but neglected, determinant is marketer actions and the question of whether and how they can contribute to persuasion knowledge development. The prevalent and intensive use of marketing and advertising in society provides several information sources—such as mass media commentary on marketing activities, advertising, and sales expertise shared by marketing professionals in the media—that can increase consumers’persuasion knowledge (Friestad & Wright, 1994). Simultaneously, too many marketing actions can lead to situations (e.g., advertising clutter) in which consumers are inhibited in developing persuasion knowledge. As mentioned above, marketer actions are not fully exogenous and also can be influenced by persuasion knowledge, that is, marketer actions can be a consequence of persuasion knowledge development. Marketers have knowledge and beliefs regarding consumers’persuasion knowledge and about consumers’understanding of persuasion practices (Moreau, Krishna, & Harlam, 2001). They might change their marketing actions and investments, depending on their perception of how changes in persuasion knowledge relate to marketing or advertising effectiveness (Nyilasy & Reid, 2009). Further research is needed to investigate the relationship between marketer actions or investments on one hand and persuasion knowledge development on the other. Such findings can provide important insights for marketers, as they might need to account for the diminishing persuasion effect through increasing persuasion knowledge when planning for increased marketing and advertising budgets. Finally, while the multilevel approach of the current meta-analysis accounts for the covariation among observations from the same data set, thereby following other recent meta-analytic applications, McShane and B¨ ockenholt (2018) have suggested an approach that accounts for the differing levels of variation among multiple dependent variables and that captures the variation and covariation that is induced by the nested structure on all levels of the analysis. This approach is better able to account for the complexity of research data as often found in consumer psychology and should be considered in future meta-analyses applied to such data. Conclusion The current meta-analysis presented a persuasion (process) perspective to answer several open research questions in the persuasion knowledge literature, as well as broaden our understanding of Persuasion Knowledge Meta-Analysis 19 persuasion knowledge in the marketplace, including its substance and effects. 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