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BY 4.0 license Open Access Published by De Gruyter Mouton September 10, 2022

The role of trustworthiness in social media influencer advertising: Investigating users’ appreciation of advertising transparency and its effects

  • Delia C. Balaban , Meda Mucundorfeanu and Brigitte Naderer
From the journal Communications


When social media influencers (SMIs) post sponsored content, it should be recognizable as such. However, there is no European Union-wide legislation governing sponsorship transparency, and monitoring practices differ significantly across member states. In Romania, where we conducted our study, such regulations are only just emerging, and there are weak monitoring policies regarding advertising disclosure on SMI branded posts. In this study, we examined how two different types of advertising disclosure commonly used on Instagram are likely to affect consumers’ behavioral outcomes, such as purchase intention and intention toward the SMI, mediated by the activation of conceptual persuasion knowledge (CPK), via negative affect and the trustworthiness of the SMI. We conducted a three-level between-subjects online experiment (N=248), manipulating the absence versus the presence of advertising, which came in one of two types, brand-unspecific (#ad, #sponsoredpost) and brand-specific (paid partnership with [brand]). Considering the mediation path via the trustworthiness of the SMI, findings suggest that the paid partnership disclosure had positive outcomes for purchase intention and intention toward the SMI.

1 Introduction

Consumer trust in traditional advertising has decreased during the last decades (Nielsen, 2015). Therefore, advertisers are constantly seeking new ways of promoting products and services to consumers (Boerman, Kruikemeier, and Zuiderveen Borgesius, 2017). Social media platforms have become a relevant environment that through native advertising provides less intrusive ways of advertising than traditional media outlets (Minton, Lee, Orth, Kim, and Kahle, 2012).

Furthermore, the popularity of social media influencers (SMIs) has grown exponentially in recent years (DeVeirman, Cauberghe, and Hudders, 2017). SMIs play a complex role because they are simultaneously celebrities, experts, and fellow consumers (Campbell and Farrell, 2020). As potential opinion leaders (Enke and Borchers, 2019; Liljander, Gummerus, and Söderlund, 2015), SMIs are assumed to be able to influence their audiences’ opinions and choices through their expertise, their authentic identities, and the intimate bonds they have with their online communities (Hudders, De Jans, and De Veirman, 2020). Today, advertisers are investing an increasingly greater portion of their budgets in influencer marketing because SMIs can generate brand engagement at a fraction of the cost of traditional advertising campaigns (Evans, Phua, Lim, and Jun, 2017; Hwang, K. and Zhang, 2018; Phua, Seunga, and Kim, 2017). SMIs are typically compensated for promoting brands in their posts (Campbell and Grimm, 2019).

In general, commercial and noncommercial posts made by SMIs have a similar style and format, and both are shared with followers (Boerman, Willemsen, and Van Der Aa, 2017). Advertising posts can be directly created and disseminated either by production companies through their social media accounts, or by SMIs or celebrities who have a large follower base (Mayrhofer, Matthes, Einwiller, and Naderer, 2019). Posts on SMI accounts gain more attention than posts on brand accounts (Campbell and Farrell, 2020), and they generate more affective brand outcomes. However, posts on brand accounts stimulate greater source credibility (De Jans, van de Sompel, De Veirman, and Hudders, 2020).

Consumer advocates question the fairness of sponsored content on SMI posts (Cain, 2011; Campbell and Grimm, 2019) because users can have difficulties distinguishing between commercial and noncommercial posts (Kay, Mulcahy, and Parkinson, 2020; Mayrhofer et al., 2019), especially when they appear one after the other (Evans, Wojdynski, and Hoy 2019). Sponsored content shared by SMIs on Instagram is typically well integrated into their surrounding content. As users might not recognize the persuasive attempts and therefore cannot guard themselves against being influenced by these messages, ways to make these techniques easier to detect are being discussed by researchers, customer protection organizations, and policy-makers (Boerman, Willemsen, et al., 2017). Several western European countries have introduced regulations that ensure that marketers promote their brands and reach their target audiences through transparently labeled sponsored Instagram SMI posts. Both consumer advocate organizations and researchers emphasize the importance of SMIs disclosing any financial relationships with a brand to make social media users aware that what they see is advertising (Boerman, Willemsen, et al., 2017; Taylor, 2017). In the USA the first regulation requiring the explicit disclosure of advertising content on social media was introduced by the Federal Trade Commission in 2013 (FTC, 2013) and was updated in 2016 (Electronic Code of Federal Regulations, 2016) and 2017 (FTC, 2017). Self-regulatory bodies such as the European Advertising Standards Alliance (2018) have stressed the importance of clearly disclosing advertising content in European Union member states. The appropriate disclosure of advertising is currently being debated in several European countries, some of which have already implemented advertising codes of conduct stipulating those commercial messages on social media should always be recognizable as such (Boerman et al., 2017).

Although there seems to be broad consensus on the importance of disclosure, how such disclosure should look has still not been agreed upon. Policy measures and regulations should be introduced to protect consumers from undisclosed persuasive messaging (Hudders et al., 2020). Advertising disclosures must come in a form that effectively helps consumers recognize sponsored content, an idea that policy makers must keep at the forefront of their thoughts. What brands, SMI agencies, and SMIs themselves consider proper advertising labeling, however, might not necessarily be perceived the same way by consumers. Disclosures of sponsored SMI posts come in diverse forms that use different sizing, language, or positioning, all of which have an impact on advertisement recognition. Advertising disclosures should be clear, conspicuous (Campbell and Grimm, 2019), and easily recognizable to all audience groups. The mere placing of disclosure among a group of other hashtags, a common practice, does not contribute to advertising recognition (Wojdynski and Evans, 2016). Understanding advertising techniques plays an important role in coping with ads on social media in the case of children and adolescents, who are frequently targeted by influencer advertising campaigns (De Jans, Cauberghe, and Hudders, 2018; Zarouali, Ponnet, Walrave, and Poels, 2017). Disclosure should be clear considering that children and adolescents have difficulties in recognizing embedded advertising (Boerman and van Reijmersdal, 2020; Rozendaal, Opree, and Buijzen, 2016; Van Dam and van Reijmersdal, 2019).

The issue of disclosing advertising on social media is on the public agenda in several European countries such as Germany, where the media have reported on several lawsuits in which well-known SMIs were accused of not adequately, or not at all, disclosing advertising content in their Instagram posts (Manager Magazin, 2019). To date, the European Union has not mandated the disclosure of social media advertising, a surprising fact given that other forms of embedded advertising, such as product placement, are already regulated (Ginosar and Levi-Faur, 2010; Spielvogel, Naderer, and Matthes, 2020). Furthermore, in some countries, laws about disclosing advertisements on social media are somewhat ambiguous because they do not state in which cases sponsored SMI posts should be labeled or the precise wording that should be used.

As several studies have confirmed, disclosing sponsored SMI content on different social media platforms such as Facebook (Boerman, Willemsen, et al., 2017; Mayrhofer et al., 2019), Twitter (Hayes, Golan, Britt, and Applequist, 2020), YouTube (Janssen and Fransen, 2019), and Instagram (Evans et al., 2017) has an impact on the attitudes and behavior of users. Findings have shown that disclosing sponsored content in native advertising significantly contributes to users’ recognizing such messages to be advertisements (Boerman, 2020; Boerman et al., 2017; De Jans et al., 2020; De Veirman and Hudders, 2020; Evans et al., 2017; van Reijmersdal et al., 2020), hence activating conceptual persuasion knowledge (CPK). This in turn can have an impact on affective and behavioral outcomes (Eisend, van Reijmersdal, Boerman, and Tarrahi, 2020; Hudders et al., 2020). However, as the SMI advertising market has matured, studies have discovered that advertising disclosure does not necessarily have a negative impact on behavioral outcomes (De Jans et al., 2020). Transparency mitigates the negative effects of ad recognition (Evans et al., 2019) and has a positive impact on perceived product efficacy and purchase intention (Woodroof, Howie, Syrdal, and VanMeter, 2020). The positive effects of advertising disclosure on purchase intention, mediated by product knowledge and attractiveness, have also been reported (Kay et al., 2020).

Due to the plethora of studies in this field, one might ask about the relevance of an additional study on this topic. There is still a remaining need for replication. The main contribution of our study is to emphasize the role of SMIs’ trustworthiness in SMI advertising. This is an important element in how audiences perceive SMIs (Balaban and Mustățea, 2019) and therefore mediates the effectiveness of advertising (Schouten, Janssen, and Verspaget, 2020). The literature has underlined the link between trust in SMIs’ branded content and affective and behavioral outcomes (Lou and Yuan, 2019), stating that sponsorships can harm the trustworthiness of SMIs under certain conditions (e. g., when audiences believe there is too much sponsored content; Hudders et al., 2020; Konstantopoulou, Rizomyliotis, Konstantoulaki, and Badahdah, 2019). In the context of the activation of CPK caused by advertising disclosure, we focused on the impact that the trustworthiness of an SMI can have on advertising-related behavioral outcomes in the presence of an affective reaction.

Furthermore, this study examines how two types of frequently used disclosures—the “#ad #sponsoredpost” disclosure and the Instagram standardize “paid partnership with [brand]” disclosure—affect the impact of SMIs’ sponsored content posted on Instagram. By comparing those types of disclosure, we aimed to exceed the scholarship on advertising disclosure on Instagram. As several studies looked at the effect of disclosures in the form of a hashtag, the recently introduced paid partnership feature was not yet in the focus of the research (De Jans et al., 2020). Our research goals are threefold. First, we seek to examine whether advertising disclosures activate consumers’ CPK (e. g., Evans et al., 2017), causing them to critically assess persuasive messages. Following Mayrhofer et al. (2019), we refer to this as negative affect. Second, we wish to gain insights into the process through which advertising disclosures are likely to influence the trustworthiness of the SMI that disseminated the sponsored post via the activation of persuasion knowledge and the negative affect (van Reijmersdal et al., 2016). Third, we desire to examine how an SMI’s perceived level of trustworthiness impacts consumers’ behavioral intentions, such as purchase intention and their intention toward the SMI (the intention to follow the SMI, to see more of his or her posts, and to learn more about the SMI). Therefore, this study can potentially provide important insights for policymakers, marketers, SMIs, and the public.

Another unique feature of the present study is its context: It was conducted in Romania, a country where the public, with the exception of those who follow international SMIs, is not accustomed to seeing advertising disclosure messages in the sponsored posts of national SMIs. Although some Romanian SMIs are active on several platforms and enjoy large audiences (Starngage, 2020), there are no laws regulating social media advertising to date, so advertising disclosures are rarely encountered. Recently, the media have put this issue on the public agenda (Bumb, 2020). Because disclosing sponsored content is not a common practice for national SMIs, we used real Instagram posts from the account of an experienced international SMI as stimulus materials. This also contributed to the external validity of the experiment and enhanced the contribution of the present study to research in the field, which has mostly relied on lookalike SMI Instagram posts in the experimental designs.

2 Literature review

Advertising disclosures and CPK

The goal of advertising disclosures is to inform the audience about persuasive attempts (Boerman and van Reijmersdal, 2020; Hudders et al., 2020; Matthes and Naderer, 2015). According to the Persuasion Knowledge Model, consumers develop knowledge or beliefs about the tactics and goals of persuasive communication during their life and can activate this knowledge to cope with further persuasive attempts. Rather than being a measure of resistance to advertising, persuasion knowledge (PK) reflects the self-control or competency of individuals when exposed to promotional techniques (Friestad and Wright, 1994). CPK, in particular,0, is often employed to elaborate on the effects of advertising disclosure on native advertising and, in particular, on SMI advertising (Boerman, Willemsen, et al., 2017; De Jans et al., 2020; Evans et al., 2017; Mayrhofer et al., 2019).

In their meta-analysis of advertising disclosures in sponsored content, Eisend et al. (2020) emphasized that in the majority of studies examined they observed two main components of PK: the conceptual and the attitudinal dimension. The former leads to CPK, whereas the latter contributes to forming critical attitudes. In the present study we focus on CPK as we consider fostering understanding of the persuasive intent of social media messages as the main purpose of disclosures (Boerman, Willemsen, et al., 2017).

Hence, advertising disclosures have the goal of informing consumers about the use of advertising tactics and therefore serve as a prime indicator of being confronted with a persuasive message. Past studies have demonstrated that the presence of a disclosure typically leads to an increase in audiences’ CPK (Boerman, 2020; Boerman, van Reijmersdal, and Neijens, 2012; Campbell, Mohr, and Verlegh, 2013; Evans et al., 2017; Wojdynski and Evans, 2016). We, therefore, hypothesize the following:

H1: The presence of an advertising disclosure on a branded SMI post will lead to higher levels of CPK compared to a branded post without an advertising disclosure.

The role of disclosure elaborateness

The existing body of literature on disclosures distinguishes between several types of disclosures. Disclosure content, timing, and awareness have been identified as boundary conditions for disclosure effects (Eisend et al., 2020). Standardized disclosures effectively increase ad recognition compared to when no disclosure is provided (De Veirman et al., 2019; Evans et al., 2017). The most common type of disclosure is brand-specific disclosure in which the brand that is responsible for sponsoring the content is mentioned (Boerman et al., 2012; Boerman, van Reijmersdal, and Neijens, 2015b; van Reijmersdal, Tutaj, and Boerman, 2013). Furthermore, in practice and research, we also find examples of brand-unspecific placement disclosures (Boerman, van Reijmersdal, and Neijens, 2015a; De Jans et al., 2020; De Veirman, Hudders, and Nelson, 2019; Kay et al., 2020; Matthes and Naderer, 2015; Mayrhofer et al., 2019). The persuasive nature of the content is suggested by words such as “sponsored” and “contains product placements” without mentioning the brand (Campbell et al., 2013). Finally, certain disclosures only present abbreviations or logos that hint at the persuasive nature of the content, such as the “PP” logo, which is used in Great Britain and is supposed to make people aware of product placement (Tessitore and Geuens, 2019).

Concerning the different forms of disclosures, we already know that the elaborateness of the information provided in the disclosure is important when it comes to the audience’s ability to recognize persuasive messaging. Explicit, visually prominent disclosures rather than clear wording and explicit disclosures (containing, e. g., the terms “advertising” and “sponsored content”) rather than implicit disclosures (e. g., “brand voice” and “presented by”) lead to superior recognition of native advertising (Wojdynski and Evans, 2016). Labeling disclosures (e. g., “sponsored by”) also improves ad recognition (Jung and Heo, 2019; Wu et al., 2016). Hence, warning symbols are not as effective as more explicit, detailed disclosures (Tessitore and Geuens, 2019). Janssen and Fransen (2019) demonstrated that in the case of YouTube videos, explicitly worded disclosures were more likely than simply worded disclosures to activate consumers’ CPK, whereas Jung and Heo (2019) found that a) the explicitness of a disclosure’s wording did not affect advertising recognition, meaning that people were able to recognize advertising based on their experience or the context, even without disclosure, and b) the explicitness of disclosure did not affect how consumers viewed the advertising, that is, the wording alone was not sufficient to activate a defense mechanism. On the contrary, Amazeen and Wojdynski (2018) found that visually prominent, clearly worded, explicit disclosures facilitate the recognition of native advertising.

Overall, prior research on both traditional and nontraditional media has found a positive relationship between disclosure presence and PK (Evans et al., 2017). Furthermore, the results of previous studies indicate that disclosures featuring clear wording, such as “advertisement” or “sponsored,” lead to higher PK compared to ones containing more ambiguous language or abbreviations (Tessitore and Geuens, 2019; Wojdynski and Evans, 2016). Advertising disclosure also contributes to greater brand recall (Eisend et al., 2020). These findings are based on the theoretical idea of obtrusiveness and specificity that increase awareness and thus memory measures (Gupta and Lord, 1998).

Commonly used disclosures on Instagram contain clear terms such as “paid ad” or “sponsored” (Evans et al., 2017). Brand-specific disclosures have been reported to have a positive impact on ad recognition and brand memory because the name of the brand is included in the disclosure. However, this does not necessarily lead to better attitudinal and behavioral outcomes (Eisend et al., 2020). Instagram offers SMIs the possibility to tag the promoted brand and simultaneously to disclose the ad by inserting the phrase “paid partnership with [brand]” above posts. In addition to this brand-specific type of disclosure, SMIs also commonly use brand-nonspecific forms of disclosure. Hence, they use hashtags such as #ad and #sponsored below the post (De Jans et al., 2020).

Based on differences in the prominence of disclosures and the varying levels of naming and not naming the brand, we expect that disclosures affect CPK as well as the memory for the specific brand. Therefore, we posit the following:

H2: A specific, elaborate advertising disclosure in the form of a paid partnership disclosure in a branded post will lead to higher CPK compared to a brand-unspecific advertising disclosure using only a hashtag disclosure.

H3: A specific, elaborate advertising disclosure in the form of a paid partnership disclosure in a branded post will lead to greater brand memory compared to a brand-unspecific advertising disclosure using only a hashtag disclosure.

Affective responses

Besides the conceptual components of PK there is also an evaluative dimension that includes critical attitudes (Boermann et al., 2012; Boerman, van Reijmersdal, Rozendaal, and Dima, 2018; Rozendaal, Lapierre, van Reijmersdal, and Buijzen, 2011). When consumers recognize certain content as advertising, it is assumed that they develop coping mechanisms, which can include heightened skepticism, resistance, and counterarguing (Evans et al., 2017). Affective responses, such as negative affect, are described as moods and feelings, and when positive or negative feelings occur after being exposed to an ad, they can predict the effectiveness of the ad (Edell and Burke, 1987). When recognizing persuasion attempts as such, people strive to maintain their freedom of choice and hence try to resist being manipulated (Wei, Fischer, and Main, 2008). Along with counterarguing, selective exposure, social validation, and source derogation, negative affect has been found to be one of the most prevalent strategies for resisting persuasive messages (Zuwerink and Cameron, 2003).

Disclosing an advertisement might trigger skepticism and emotional responses such as negative affect in social media consumers, who may be annoyed by an SMI’s attempts to make money (Audrezet, de Kerviler, and Moulard, 2020). Such a reaction, however, is not a given. Previous studies also indicate that when consumers recognize the persuasive intent of a post due to an advertisement disclosure, they may view such messages as transparent, which consequently positively affects the credibility of the sponsor (Hwang and Jeong, 2016). As most studies still propose a positive mediation path of CPK on negative affect (e. g., Mayerhofer et al., 2020), we assume that:

H4: Advertising disclosures meditated through CPK lead to the occurrence of negative affect.

The trustworthiness of the SMI

Defined as the integrity and believability of a communicator (Erdogan, 1999), trustworthiness is an important element of the source expertise of SMIs (Hudders et al., 2020; Shan, Chen, and Lin, 2019). SMIs need to ensure their trustworthiness to effectively endorse products and services (Schouten et al., 2020). The perceived trustworthiness of the source is believed to be a primary factor that determines subsequent behavior (Berger, 2014; Swanepoel, Lye, and Rugimbana, 2009).

Existing studies on SMI advertising indicate that perceived trustworthiness can be affected by a lack of transparency (Audrezet et al., 2020). In the case of SMI advertising, a lack of disclosure masks the advertiser’s intent to persuade and may be interpreted as a way of taking advantage of followers’ trust (Campbell and Marks, 2015). It is often viewed with suspicion by the general public and is considered to be a form of deception (Lazauskas, 2014). Transparency and openness lay the foundation for a trusting relationship and make advertising more successful in the long run (Evans et al., 2019). Campbell and Marks (2015) and Chu and Kamal (2008) have found that there is a positive correlation between blogger trustworthiness and followers’ attitudes toward the brand.

Based on this line of argumentation, Boerman, Kruikemeier, et al. (2017) have noted that becoming aware of the persuasive intent of a post (i. e., PK) due to an advertising disclosure and mediated through a negative affective reaction (i. e., negative affect) could potentially downgrade the trustworthiness of an SMI. Thus, we hypothesize the following:

H5: a) Advertising disclosures increase effect on CPK, and therefore, b) increased negative affect decreases the trustworthiness of an SMI.

In the field of SMI advertising, trustworthiness is essential because it directly influences and affects the consumer’s decisions about promoted products and SMIs’ commercial offerings in general (Balaban and Mustățea, 2019). Previous studies have demonstrated that when bloggers disclose sponsorships it can influence behavioral intentions such as purchase intention, continued interest in the blogger (Liljander et al., 2015), and the credibility of the blogger, measured as trust (Colliander and Erlandsson, 2015).

Recent studies on SMI advertising have also reported the positive indirect effects of advertising disclosure on brand attitude, which is subsequently mediated by ad recognition, skepticism, and source credibility (De Veirman et al., 2019). The latter is a concept that is close to trustworthiness, according to the SMI source credibility approach (Hudders et al., 2020). Furthermore, mediated by affective advertising literacy via SMIs’ trustworthiness and via para-social interaction, advertising disclosure has been found to have a positive impact on adolescents’ behavioral intentions (De Jans et al., 2018).

Therefore, we are interested in understanding the process through which sponsorship disclosure on Instagram is likely to affect behavioral intentions both toward the brand and the SMI. Intention toward the SMI is an indicator that consists of the intention to follow his or her social media account, to learn more about the SMI, and to see more of his or her published content on social media. A similar indicator is also used to study bloggers (Liljander et al., 2015). In line with this, we formulate the following hypothesis:

H6: Advertising disclosures mediated by CPK, via negative affect and trustworthiness of the SMI, have a negative effect on purchase intentions and intentions toward the SMI.

We visualize the full hypothesized model in Figure 1.

 Figure 1

Figure 1

3 Method

In this study we examine advertising disclosures in sponsored SMI posts. We compare the effects of three different types of advertising disclosures (including no advertising disclosure) on the activation of CPK, negative affect, perceived trustworthiness of the SMI, and behavioral outcomes toward the promoted brand and the SMI itself.


As a first step, we conducted a pretest of twelve brands to assess which brand is most adequate for our research design. We aimed to choose a brand that elicited the most neutral brand evaluation so that existing brand attitudes would not have an impact on our hypotheses (Evans et al., 2017). Hence, we recruited 55 respondents, all students at a large Romanian university (63.63 % female) to rate twelve brands (Nike, Adidas, Puma, Zara, H&M, Mango, Lidl, Kaufland, Carrefour, Apple, Huawei, Samsung) on a scale from 1 to 10. Puma was rated most neutrally (M = 5.89; SD = 2.51) and hence was chosen as the target brand.

Participants and study design

A three-level between-subjects experimental design was conducted by manipulating the absence versus the presence of advertising disclosure, which came in one of two types, brand-unspecific and brand-specific. The control condition and the two experimental conditions presented the same SMI advertising posts. The difference between the experimental conditions consisted in the absence or the presence of the above-mentioned types of disclosure, that is, brand-unspecific (i. e., hashtag disclosure condition) and brand-specific (i. e., paid partnership condition) disclosure.

We recruited participants for our online survey-based experiment via social media announcements. Vouchers were given to each participant who took part in our study. In total N=248 participants (aged 16 to 42, M = 23.58, SD = 5.83, 60.9 % female) were randomly assigned one of our conditions. Out of the total number of participants, 42 % (n=104) had been following SMIs on Instagram for at least two years, both national SMIs 55.6 % (n=138) and international SMIs 63.3 % (n=157).

Stimulus materials

The stimulus material consisted of an overview of the Instagram account of Pamela Reif (an international SMI with 6.1 million followers at the time the study was conducted), followed by nine individual Instagram posts, three of which contained brand presentations. This was done based on the common practices of Instagram users. When encountering a new profile on Instagram, users usually tend to look for general information about the account available in the overview section and then scroll down to view some posts. We found that most of our participants, 89.9 % (n=223), did not follow Pamela Reif at the time of the experiment.

Participants assigned to any of the three conditions watched the same posts, the difference between the groups consisting solely in the different form of advertising disclosure in the case of the three posts containing advertising. Thus, the stimulus materials included the absence of disclosure for the control condition, the presence of textual brand-unspecific disclosure (#ad, #sponsoredpost) placed below the posts for the hashtag condition, and the presence of textual brand-specific disclosure (“paid partnership with Puma”) placed above the posts for the paid partnership condition. As we already mentioned above, the disclosure types were selected based on commonly employed practices on Instagram (Chacon, 2017; De Jans et al., 2020; Kiel and Solf, 2019). In our stimulus material, we mixed posts containing advertising with posts with no advertising, a common practice of SMIs on Instagram. This aspect of the design, therefore, contributed to the external validity of the experiment.

Depending on the condition, our participants either watched the three branded posts without an advertising disclosure (control condition; n=81), with a disclosure including the hashtags #ad and #sponsoredpost (hashtag condition) at the end of the text below the picture (n=81), or with a disclosure stating “paid partnership with Puma” (paid partnership condition) written above the picture (n=86). For an overview of the stimulus material, see the Appendix. The hashtag disclosure differs from the paid partnership disclosure in two important aspects: a) the positioning of the text and b) the reference to the sponsored brand. While comparing these two types of disclosures, which differ in not one but two aspects, does slightly diminish the internal validity of the experiment, the design ensures its external validity, as the tested disclosures are the two most common ways to mark a sponsored SMI post on Instagram (Chacon, 2017; Kiel and Solf, 2019).


Mediators. For our mediators, we measured three concepts: CPK, negative affect, and trustworthiness of the SMI. The first two constructs were measured on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). The activation of CPK was measured using three statements (e. g., “These Instagram posts present advertising”; α=.86, M=5.35, SD=1.28; van Reijmersdal et al., 2016). Negative affect was measured using three statements (e. g., “While looking at the posts I felt annoyed”; α=.92, M= 2.01, SD=1.26; van Reijmersdal et al., 2016). Trustworthiness of the SMI was measured using six 7-point semantic differential scales, which rated the SMI on a scale ranging, for example, from 1 (dishonest) to 7 (honest; α=.93, M=4.69, SD=1.21; Liljander et al., 2015).

Dependent Variables. As brand memory we consider brand recall that was measured with an open-ended question (“What brand did you recognize in the posts?”) and coded the answers using a dummy variable (1 = Puma, 0 = other brands or no brand recall; 47.2 % [n=117] recalled seeing Puma).

We used two constructs as independent variables: purchase intention and intention toward the SMI. Purchase intention was measured using four statements (e. g., “I will buy a product from Puma”) on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree; α=.90, M=3.94, SD=1.47; van Reijmersdal et al., 2016). Intention toward the SMI was measured using three statements (e. g., “I would follow this Instagram profile”) on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree; α=.87, M=5.12, SD=1.19; Liljander et al., 2015).

Confound checks

A series of confound checks for gender (χ2(2)=1.43, p=.490, Ф=.08), education (χ2(6)=11.95, p=.288, Ф=.22), age (F(2, 248)=1.35, p=.26), Instagram use (F(2, 248)=0.09, p=.912), following Romanian SMIs on Instagram (χ2(2)=2.87, p=.238, Ф=.11), following international SMIs on Instagram (χ2(2)=11.86, p=.394, Ф=.09), and following Pamela Reif (χ2(2)=0.70, p=.704, Ф=.05) showed that differences in the outcome variables are not a result of inherent differences between conditions.

Table 1:

Frequency (absolute and relative) of disclosure recognition per conditions.

Observed form of disclosure

Control group

n (%)

Hashtag condition

n (%)

Paid partnership condition

n (%)

No disclosure

45 (55.55)

49 (60.5)

39 (45.35)

#ad, #sponsoredpost

28 (34.57)

26 (32.1)

15 (17.44)

Paid partnership with Puma

 8 (9.88)

 6 (7.4)

32 (37.21)


81 (100)

81 (100)

86 (100)

4 Results

Manipulation check

To assess whether our manipulation was successful, we checked for significant differences in disclosure recognition. We asked the participants the closed question “Did you see one of the following indications in the posts below?” and gave them three possible responses (“no ad indication”, “#sponsoredpost or #ad”, and “paid partnership with a brand”). We observed significant differences between the conditions (χ2(4)=31.91, p<.001, Ф=.36). Thus, 55.55 % (n=45) of the participants assigned the nondisclosure condition reported to not have seen any disclosure. In terms of the experimental conditions, 32.1 % (n=26) of the participants assigned the hashtag condition and 37.21 % (n=32) of the participants assigned the paid partnership condition reported to have seen the correct type of advertising disclosure. Ad recognition scores are presented in Table 1.

Main results

We ran a MANOVA, with advertising disclosure (control condition, hashtag disclosure condition, and paid partnership disclosure condition) as the fixed factor, and CPK, negative affect, trustworthiness of the SMI, purchase intention, and the intention toward the SMI as dependent variables. The means for each condition are shown in Table 2.

Advertising disclosure proved to have a significant effect on the mediators and outcome variables (Wilks’ Lambda=.82, F(10, 248)=5.03, p<.001, ηp2=.10). We observed significant main effects of our experimental conditions on CPK (F(2, 248)=3.62, p=.03, ηp2=.03) and on purchase intention (F(2, 248)=20.59, p<.001, ηp2=.144). Advertising disclosure had no significant main effects on negative affect, on the trustworthiness of the SMI, and on the intention toward the SMI.

Table 2:

Descriptive statistics for experimental conditions.

Control group


Hashtag condition


Paid partnership condition



Conceptual persuasion knowledge

5.19 (1.29)c

5.21 (1.41)c+

5.66 (1.09)a, b+

F(2)=3.62; p=.028; η=.03

Negative affect

1.93 (1.13)

2.05 (1.30)

2.07 (1.36)

F(2)=0.30; p=.742;


Trustworthiness of the SMI

4.79 (1.24)

4.69 (1.30)

4.60 (1.16)

F(2)=0.53; p=.589;


Intention towards the SMI

3.41 (1.96)

3.24 (1.97)

3.12 (1.96)

F(2)=0.46; p=.630;


Purchase intention

4.40 (1.30)c

4.29 (1.51)c

3.18 (1.27)a, b

F(2)=20.59; p<.001;


Note: N=284; a, b, c group differences p<.050; + p<.070.

Post-hoc tests revealed that the paid partnership disclosure significantly increased CPK compared to the control condition (p=.041). We also observed a marginally significant main effect (p=.068) between the paid partnership condition and the hashtag condition. The control condition and the hashtag condition did not significantly differ from each other (p=1.00). These findings partially support H1, which posits that advertising disclosures have a significant effect on CPK compared to no disclosures. H2 posits that brand-specific advertising disclosure significantly increases CPK compared to brand-unspecific disclosure. Our main analysis showed marginally significant proof of such a relationship.

The MANOVA furthermore indicates that the disclosure condition had a non-hypothesized main effect on purchase intention. We observed that the paid partnership condition group had significantly lower levels of purchase intention compared to the control group (p<.001) and the hashtag condition group (p<.001). Yet the control group and the hashtag condition group did not significantly differ from each other (p=1.00). We will discuss this effect in detail in the full model analysis.

We also ran a chi-square test to examine the effect of our conditions on brand memory. We observed significant differences in brand memory between the three conditions (χ2(2)=8.16, p=.017, Ф=.02). Participants assigned the paid partnership disclosure condition had the highest level of brand memory (59.3 %, n=51), followed by those with the hashtag disclosure condition (43.2 %. n=35) and the control group (38.3 %, n=31). A logistic regression analysis indicates that while the hashtag condition group and the control condition group did not differ from each other (b=.21; p=.523), the paid partnership condition increased brand memory compared to the hashtag condition (b=.65; p=.038) and the control (b =.86; p=.007). This finding lends support to H3, which assumes higher brand memory in the brand-specific paid partnership condition compared to the brand-unspecific hashtag condition.

Statistical model

To test the proposed hypotheses about the mediating effect of the activation of CPK, via negative affect and via the trustworthiness of the SMI, on a) purchase intention and on b) the intention toward the SMI, we ran a mediation analysis using Model 6, PROCESS macro 3 in SPSS (Hayes, 2017), employing 1,000 bootstrap samples. The control group was used as a reference group to display the effects of the two disclosure conditions. Furthermore, we chose to include gender as a covariate in our model, as the SMI in our employed stimulus material was a female SMI, and we also had male participants. Detailed results can be found in Table 3.

Data analysis

Effects on CPK. As we already highlighted in the main effect analysis, we found that CPK was higher only with the paid partnership condition compared to the control group (b=0.46, p=.019, LLCI=0.08, ULCI=0.86). The hashtag condition group did not significantly differ from the control group (b=0.02, p=.915, LLCI=–0.37, ULCI=0.42). Hence, as also highlighted in the main effect analysis, not all types of disclosure can increase CPK (only partial support for H1). To examine our second hypothesis, which posits that a specific, elaborate advertising disclosure in the form of a paid partnership disclosure in a branded post will lead to higher CPK compared to a brand-unspecific advertising disclosure using only a hashtag disclosure, we ran the same model including the hashtag condition as a reference group. The paid partnership condition significantly increased CPK compared to the hashtag condition (b=0.45, p=.024, LLCI=0.06, ULCI=0.83), lending support to H2. No additional effects were observed with this new model.

Effects on negative affect. We found in the experimental conditions no direct effect on negative affect compared to the control group. Against our expectations (H4), we found CPK to have only a marginally significant effect on negative affect (b=0.12, p=.066, LLCI=–0.01, ULCI=0.24).

Table 3:

Results of the analysis.

Conceptual persuasion knowledge

Negative affect

Trustworthiness of the SMI

Purchase intention

Intention toward the SMI









b SE

Hashtag condition









–0.19 0.25


partnership condition









–0.30 0.25










0.17 0.21

Conceptual persuasion knowledge







–0.18* 0.09

Negative affect





–0.36*** 0.09

Trustworthiness of the SMI



0.75*** 0.09








Note: Macro PROCESS 3, Model 6 with 1,000 bootstrap sample; Calculated separately for purchase intention and intention directed toward the SMI; N = 248; Control group inserted as a reference group*** p <.001; ** p <.01; * p <.05 + p <.07.

Effects on the trustworthiness of the SMI. Concerning our third mediator, the trustworthiness of the SMI, we again found no direct impact of either experimental condition compared to the control group. However, against our expectations (H5a) the activation of CPK had a direct positive influence on the trustworthiness of the SMI (b=0.34, p <.001, LLCI=0.22, ULCI=0.46). This finding suggests that increased CPK creates transparency, which does not, as hypothesized, deteriorate trust because a persuasive intent is uncovered. In fact, our study participants seemed to appreciate transparency. The indirect effect path of the sponsored partnership disclosure via CPK and trustworthiness was positively significant (b=.02, SE=.02, LLCI=.01, ULCI=.06). Furthermore, we observed that negative affect decreased the trustworthiness of the SMI (b=–0.33, p<.001, LLCI=–0.45, ULCI=–0.21), yet in our study negative affect was not impacted by the disclosure conditions or CPK. Hence, H5b was not supported.

Effects on purchase intention. We found, as already mentioned in the main analysis, that the paid partnership condition had a direct negative impact on purchase intention in comparison to the control condition (b = –1.31, p<.001, LLCI=–1.72, ULCI=–0.89). This finding suggests that disclosure is a negative predictor for brand outcomes. The hashtag condition, however, did not influence participants’ purchase intentions when it came to the advertised brand (b=–0.16, p=.446, LLCI=–0.58, ULCI=0.26) compared to the control group. Neither CPK nor negative affect had a direct effect on purchase intention. The trustworthiness of the SMI, however, had a direct positive effect on purchase intention (b=0.17, p=.024, LLCI=0.02, ULCI=0.31).

Intention toward the SMI. For our second dependent variable, we found no direct effects of the two experimental conditions. CPK, however, had a direct negative effect on the intention to follow the SMI (b=–0.18, p=.041, LLCI=–0.34, ULCI=–0.10). Negative affect also had a direct negative effect on the intention toward the SMI (b=–0.36, p <.001, LLCI=–0.53, ULCI=–0.19). Furthermore, the trustworthiness of the SMI had a positive effect on the intention toward the SMI (b=0.75, p<.001, LLCI=–0.58, ULCI=0.92).

Mediation analysis. The full mediation pathway via CPK, negative affect, and trustworthiness of the SMI on our two dependent variables was not significant due to the marginally significant effects on negative affect. However, the mediation pathway of the effects of advertising disclosure via CPK and the trustworthiness of the SMI on purchase intention was significant, although this finding only applies for the paid partnership condition (b=0.03, SE=0.02, LLCI =0.01, ULCI=0.07). This result suggests that transparent sponsored SMI posts with paid partnership disclosures increase CPK compared to posts with no disclosure and that this heightened CPK in turn positively impacts the trustworthiness of the SMI, which can have positive outcomes for the promoted brand. This finding goes against our expectations formulated in H6a. A less elaborate disclosure (i. e., hashtag disclosure) did not have the same effect.

We found the same mediation pathway of the effects of the paid partnership condition compared to the control condition via CPK and trustworthiness of the SMI on the intention toward the SMI (b=0.12, SE=0.57, LLCI=0.01, ULCI=0.24). Hence, a paid partnership disclosure can positively affect the intention toward the SMI when considering the mediation of CPK and trustworthiness. This finding therefore does not support H6b. Hypotheses testing with coefficients is presented in Figure 2.

 Figure 2

Figure 2

5 Discussion

In line with previous research, our findings underlined that brand-specific advertising disclosure on Instagram (i. e., “paid partnership with [brand]”) can foster CPK and brand memory in the form of recall (Boerman, Willemsen et al., 2017; Mayrhofer et al., 2019). Our results demonstrate that even in a country where users are not particularly accustomed to advertising disclosures, paid partnership disclosures clearly communicate the persuasive intent of the messages they are attached to.

With few exceptions (Evans et al., 2017), previous studies on disclosure practices on Instagram have compared the absence of a disclosure with the presence of a single type of disclosure. Hence, our study contributes to the existing body of literature by putting two frequently employed disclosures (Chacon, 2017; Kiel & Solf, 2019) to the test. Our study indicates that more elaborate, explicit disclosures activate social media users’ CPK with greater success than hashtag disclosures. Hence, visually prominent, brand-specific disclosures are more likely to be recognized and remembered (Wojdynski and Evans, 2016).

Similar to the findings of other studies, our results emphasize that advertising disclosures do not automatically lead to a decrease in brand outcomes such as purchase intention, (e. g., De Jans et al., 2020; Kay et al, 2020; Mayrhofer et al., 2019; Woodroof et al., 2020). Instead, we found a positive brand effect, as the paid partnership disclosure increased brand memory more significantly than no disclosure or hashtag disclosure.

Moreover, advertising disclosures do not automatically have a negative effect on intentions toward the SMI (Liljander et al., 2015). By differentiating between a cognitive and an affective path, we present a rather complex image of how disclosures affect the brand and the communicator. Our results indicate that, in terms of comparing the cognitive and the affective PK mediation paths, SMI ads have similar effects compared to traditional television commercials and advergames. A study conducted on children’s and teens’ interactions with television commercials suggests that liking the advertising format could counter the negative effects of persuasive understanding (Neyens, Smits, and Boyland, 2017). We found that the paid partnership condition, compared to the control, had a direct negative effect on users’ intentions to purchase the target brand and also had a positive effect on the mediation path. Thus, disclosure can potentially have a negative effect on users’ intentions to purchase advertised brands (e. g., Evans et al., 2017; Mayrhofer et al., 2019). Although our study examined relevant mediators in this process, there are still other affective processes that we did not consider which could explain the negative direct effect of the conditions we observed (Zuwerink and Cameron, 2003).

When examining the hypothesized mediation path, we found that the activation of CPK increases the trustworthiness of the SMI, which has positive outcomes for the advertised brand. Hence, paid partnership disclosures contribute to identifying advertising messages and also affect the perceived transparency and trustworthiness of social media SMI advertising, something that is appreciated by social media users (Campbell and Evans, 2018; Evans et al., 2017; Johnson, Potocki, and Veldhuis, 2019). Such positive perceptions boost users’ intentions to purchase the target brand and their intentions toward the SMI. While the picture concerning brand outcomes and SMI intentions is rather nuanced, adding a paid partnership disclosure is an appropriate measure for ensuring that sponsored SMI posts on Instagram are clearly and comprehensively marked. Instagram users who recognize the persuasive intent of a trusted SMI can follow them, or continue to follow, and are willing to see more of the SMI’s content. Hashtag disclosures, however, fall short when it comes to adequately informing consumers.


Our study also has its limitations. The first pertains to the short exposure to our stimuli. On the one hand, longer exposure to the SMI’s posts and stimuli could perhaps lead to participants’ becoming more immersed in the SMI’s activities on Instagram, which would make the experience more realistic. On the other hand, a longitudinal study could better explain the long-term implications of advertising disclosure, the trustworthiness of the SMI, purchase intention, and intention toward the SMI. In addition, we only tested the effects of one SMI, and we only used a female SMI. We controlled for the impact of gender and found no effect. However, replications that consider different SMIs and different target groups would be insightful.

Second, the observed direct effect of the paid partnership condition on purchase intention suggests other affective processes that we did not consider in our study (Zuwerink and Cameron, 2003). Hence, future research should examine this topic even more comprehensively to increase the understanding of how disclosure affects social media users.

Third, as mentioned above, the two tested disclosures differed in more than one aspect from each other, which to some extent decreased internal validity. Yet the goal of this study was to test the effectiveness of advertising disclosures in an externally valid sense by testing two established forms of disclosures. Future studies should test the individual aspects of disclosures even more comprehensively than previously done to generate clear recommendations about the ideal disclosure. Nonetheless, our study contributed to this discussion by excluding the hashtag disclosure as an adequate solution and showing the nuanced outcomes of the paid partnership disclosure.

Implications and future research

These limitations notwithstanding, our study contributes to a better understanding of the complex mechanism of social media SMI advertising in a constantly changing social media environment. By exploring the role of CPK, negative affect, and SMI trustworthiness as mediators in the relationship between advertising disclosure and purchase intention and intention toward the SMI, we have contributed to differentiating the persuasion knowledge model.

The results of the present study also have relevant practical implications. In many European countries, legislation on brand disclosure on social media is either still in development or nonexistent. A general European Union-wide regulation has yet to be implemented. Such a law would create more legal certainty for all parties involved: legislators, sponsoring companies, SMIs, and especially consumers. To inform consumers about sponsored content, disclosure must be properly communicated. Our findings support the idea that transparency benefits not only consumers but also other stakeholders such as marketers and SMIs. The Instagram “paid partnership with [brand]” feature proved to be more efficient for ad recognition than a “#ad, #sponsoredpost” advertising disclosure placed among other hashtags. The paid partnership disclosure also allows brands to access the post’s metrics. This is the reason some SMIs avoid using it and prefer the hashtag advertising disclosure (De Jans et al., 2020). For SMIs, building trustworthiness can be the key to successful social media advertising. Our results may, therefore, be useful for developing effective and sound advertising disclosures on Instagram.


Advertising disclosures are important and do not necessarily always have a negative impact on behavioral outcomes. Instead, disclosures can increase transparency, which users appreciate. The trustworthiness of the SMI plays a key role in the relationship between the activation of CPK and evaluative outcomes. Hence, employing the most explicit and transparent advertising disclosures possible can pay off for both the sponsoring brand and the SMI.


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Published Online: 2022-09-10
Published in Print: 2022-09-07

© 2021 Delia C. Balaban et al., published by De Gruyter.

This work is licensed under the Creative Commons Attribution 4.0 International License.

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