4: Dissection of a literature review
The stand-alone literature review
In most sophomore biology classes in high schools, students are asked at one point to cut open a frog, identify the various internal organs and draw a diagram of what they find. This exercise is my intention here. I will be cutting open and revealing to you the requisite parts of a literature review. In the following section we will dissect an article that was written as a stand-alone literature review. The purpose of the literature review as its own article is to tell us where we have been on a topic, and to light the way for where the field should go next.
This specimen we will be dissecting was written by De Veirman, Hudders, and Nelson (2019). Their research focuses on the literature of social media influencers’ impact on children. Excerpts are provided for our dissection, but you can find the full article here:
De Veirman, M., Hudders, L., & Nelson, M. (2019). What is influencer marketing and how does it target children? A review and direction for future research. Frontiers in Psychology , 10.
Children nowadays spend many hours online watching YouTube videos in which their favorite vloggers are playing games, unboxing toys, reviewing products, making jokes or just going about their daily activities. These vloggers regularly post attractive and entertaining content in the hope of building a large follower base. Although many of these vloggers are adults, the number of child vloggers is flourishing. The famous child vlogger Ryan of Ryan’s World, for instance, has more than 19 million viewers and he is (at age seven) a social media influencer. The popularity of these vloggers incited advertisers to include them as a new marketing communication tool, also referred to as influencer marketing, in their marketing strategy. Accordingly, many influential vloggers now receive free products from brands in return for a mention in one of their videos and their other social media (e.g., TikTok or Instagram) and some are even paid to create a sponsored post or video and distribute it to their followers. This sponsored content appears to be highly influential and may affect young children’s brand preferences. Given the limited advertising literacy skills (i.e., knowledge of advertising and skills to critically reflect on this advertising) of children under age 12, they are a vulnerable target group when it comes to persuasion. Therefore, caution is needed when implementing this marketing tactic to target them. However, research on how influencer marketing affects young children (under 12) is scarce and it is unclear how these young children can be empowered to critically cope with this fairly new form of persuasion. This paper therefore aims to shed light on why and how social media influencers have persuasive power over their young followers. The paper starts with providing insights into how and why social media influencers became a new source in advertising. We then discuss the few studies that have been conducted on influencer marketing among young children (under 12), based on a systematic literature review, and take these findings to formulate societal and policy implications and develop a future research agenda.
In this introductory paragraph, the authors achieve three main goals. First, they provide needed background information on the issue as a contemporary problem. This article is focused on the practical implications of the theories they will summarize in this literature review. Notice they mention the various forms of media and influence and provide some examples. Second, they provide insights as to why this might be problematic, socially. They are making the case here for why research needs to be summarized so that this population of consumers can be better served (and protected). This leads them to the third goal which is to describe how their summary addresses the problems outlined in the second goal. Take note of the clearly identifiable thesis found at the end of the introduction – “This paper therefore aims to shed light on why and how social media influencers have persuasive power over their young followers.”
The purpose of this review is threefold. First, the research aims to provide insights into the importance of social media influencers as a source in advertising targeting children. In order to adopt a theoretical approach to children’s processing of influencer marketing, we draw upon existing theoretical and empirical work regarding source effects in persuasion. During childhood, children encounter different advertising sources shaping their tastes and preferences, trying to turn them into brand loyalists as they grow older. Social media influencers can be perceived as a new type of real-life endorser affecting children’s and their parents’ consumption behavior. Second, this paper provides a review of the current (limited) academic research on influencer marketing targeted at children. Additionally, societal and policy implications of this tactic in the context of prior research are discussed. Third, a future research agenda that may foster academic research on the topic is included. This way, we hope our review may provide a basis for marketing related regulation, policies, and parent intervention strategies and thus help ensure the protection of children.
The authors continue with a longer introduction to the literature review by providing specific case studies and citing the relevancy and dangers of the issue. They conclude that section with the following paragraph. You can see the practical implications of summarizing the research, and the need for the literature review in that the field is just growing and has a wide breadth of topics which have not been synthesized. This is an immature research fields that needs a scholar to categorize into themes and research tracks. The future research agenda is the primary outcome of such a literature review, but must be bolstered by the findings of the literature review itself.
The importance of the source as sender of the object of information has been well recognized in the communication and advertising literature. Already in 1948, Laswell emphasized that every communication involves a message, a medium, a recipient, and a source (Lasswell, 1948). In advertising, a distinction can be made between the one who bears financial and legal responsibility for the message and the one who communicates the brand’s message (Stern, 1994). As such, in the latter sense, brands may create or license a character or pay an endorser or spokesperson to influence consumers’ attitudes and purchase intentions. The persuasiveness of advertising is strongly influenced by consumers’ perception of these sources (see Wilson and Sherrell, 1993 for a meta-analysis). For instance, source credibility plays a critical role in how consumers evaluate brands and products, whereby a positive evaluation of the credibility of the source is likely to translate into positive advertising outcomes (Sternthal et al., 1978; Ohanian, 1991). Source credibility consists of two dimensions: trustworthiness and expertise. Trustworthiness refers to the honesty, believability, and morality of the endorser, while
expertise refers to the endorser’s competence, knowledge, and skills (Hovland et al., 1953; Sternthal et al., 1978; Erdogan, 1999; Flanagin and Metzger, 2007).
The authors now begin their review of the literature by citing the original thinkers (seminal authors). You can usually pick out seminal works by the date. A robust description of the seminal work is not needed because others reading your work will be well familiar with them. Laswell (1948) began the discussion on communication in advertising. Because this literature review is focused on advertising to children through social media influencers, this seems like a logical beginning to their literature review. Other ideas generated by early works are also cited. Stern’s (1994) work on branding, Sternhal et al’s. (1978) research on credibility in advertising, and Hovland’s (1953) empirical investigations of trustworthiness and expertise all become solid starting points for this literature review. The principles theories of these seminal works are tangentially related to the research project at hand. However, the constructs and dynamics of these theories apply in the same manner to the traditional advertising as they do for social media influence on children – that is, how is media being consumed?
Both trustworthiness and expertise have been found to enhance advertising effectiveness (Amos et al., 2008). Furthermore, the physical appearance or attractiveness of the source plays a major role in the endorsers’ credibility and, consequently, persuasiveness (Kahle and Homer, 1985; Kamins, 1989; McCracken, 1989; Ohanian, 1991). Even among children, using attractive peer models has been shown to increase advertising effectiveness (e.g., Van de Sompel and Vermeir, 2016). Source attractiveness is driven by factors such as perceived similarity, familiarity, and likeability of the source. Familiarity refers to the extent to which one knows the source through exposure; likability is defined as affection for the source as a result of the source’s physical appearance and behavior, while similarity is the supposed resemblance between the source and receiver of the message (McGuire, 1985). According to McGuire (1985), sources who are known to, liked by, and/or similar to the consumer are found to be attractive and, as a result, are persuasive. Moreover, these source factors contribute to consumers’ identification with the source, which increases the likelihood they will adopt their beliefs, attitudes, and behaviors (Kelman, 1961; Basil, 1996). When consumers identify with the source, they will likely imitate his/her behavior, including the products he/she uses (Kelman, 1961), also referred to as social learning (Bandura et al., 1961). Indeed, as sources in advertising usually show the usefulness of the product they endorse and how to use it, this action may lead to observational learning and modeling of their behavior accordingly (Bandura et al., 1966). Moreover, next to family and friends, sources used in advertising may serve as role models they refer to in their identity formation (Lloyd, 2002; Hoffner and Buchanan, 2005). As a result, when advertising sources are paired with products, the positive affective responses toward those sources may transfer onto the products (Acuff and Reiher, 1999; McNeal, 2007; de Droog et al., 2012), which has been referred to as a meaning transfer (McCracken, 1989). Importantly, crucial to the effectiveness of endorsement marketing is a good fit between the source and the product he/she endorses, which has been referred to as the match-up hypothesis in celebrity research (Kamins, 1990). To conclude, the likelihood of the former process to occur increases when consumers develop a parasocial relationship (parasocial interaction; PSI) with the source (Tsay-Vogel and Schwartz, 2014). PSI, as introduced by Horton and Wohl (1956), refers to the relationships consumers develop with media characters, making them important sources of information (Rubin et al., 1985). Accordingly, when consumers identify with a source and their brand-usage behavior, they will likely adopt this behavior (Naderer et al., 2018). As the need for companionship, which is the main driver for relationship formation, emerges in childhood (Hoffner, 2008), children typically engage in the formation of PSI’s (de Droog et al., 2012). The above theoretical insights explain the success of sources used in advertising in general. As such, this robust body of literature has demonstrated that the source in the message is important for persuasion effects. These processes may also apply to social media influencers. Before discussing how influencers may affect children, we will first provide an overview of the different sources that are used in advertising targeting children and discuss how influencers evolved as a new source in advertising.
The authors continue by exploring the field of advertising and the dynamics of theories which apply to influencing. The seminal theory of Badura (1966) on social cognition (that is, how do we learn from each other) is directly impactful on how children are being influenced by media. The last sentence of this section provides transition to the next section, which is good employment of academic writing.
The following three sections of their literature review are structured as follows:
In the next section of the literature review, the authors provide an overview of the various influencing methods which target children which include brand and licensed characters as well as celebrity and peer endorsers. In the subsequent section the authors provide an overview of social media marketing in general, with emphasis on how influencers have become credible advertising means, relatable role models, and hidden persuaders. They then establish an understanding of traditional advertising targeting children. Building upon the theories outlined in these first sections, they conclude by providing a synthesis of the literature as it relates to current research on influencer advertising towards children.
Three experimental studies examined how children are affected by sponsored vlogs and one study focused on how parents of children between the ages of four and 11 react to sponsored vlogs. First, two studies examined the impact of social media influencer marketing on children’s food intake (Coates et al., 2019a,b). The first study is a randomized trial with a between subjects design in which 176 children (9–11 years) were exposed to mock-Instagram profiles of two popular vloggers, either promoting healthy or unhealthy snacks. Results showed that influencer marketing of unhealthy foods increased children’s immediate food intake, whereas the equivalent marketing of healthy foods had no effect. In their second study, an advertising disclosure was included to alert children on the inclusion of advertising. In a between-subjects design, 151 children (9–11 years) were exposed to popular YouTubers’ vlogs including a non-food product, or an unhealthy snack with or without an advertising disclosure. Participants’ intake of the marketed snack and an alternative brand of the same snack were measured. In line with their first study, influencer marketing increased children’s immediate intake of the promoted snack relative to an alternative non-food brand (control condition). Remarkably, the inclusion of an advertising disclosure increased the effect, as children who viewed food marketing with a disclosure (and not those without) consumed 41% more of the promoted snack compared to the control group. The study of De Jans et al. (2019) examined how an educational vlog can help children (11–14 years) cope with advertising. In an experimental study (N = 160), using a two (advertising disclosure: no disclosure versus disclosure) by two (peer-based advertising literacy intervention) between-subjects design, they examined how an advertising disclosure can reduce the persuasiveness of sponsored vlogs and how watching an educational vlog moderates these effects. The results show that an advertising disclosure increased their recognition of advertising and their affective advertising literacy for sponsored vlogs, and that only affective advertising literacy negatively affected influencer trustworthiness and PSI and purchase intention accordingly. Moreover, when young adolescents were informed about advertising through an informational vlog (i.e., peerbased advertising literacy intervention), positive effects on the influencer and subsequently on advertising effects were found of an advertising disclosure. Evans et al. (2018) examined how parents of young children cope with sponsored vlogging on YouTube. They gauged parents’ understanding of and responses to sponsored child influencer unboxing videos. Through an experimental design among 418 parents, they assessed the influence of sponsorship text disclosure (present or absent) and sponsor pre-roll (sponsor pre-roll, nonsponsor pre-roll, and no pre-roll) for a toy on conceptual persuasion knowledge, perceptions of sponsorship transparency, and different outcome measures. Moreover, they explored how parental mediation influences the outcomes. They found that sponsor variations in pre-roll advertising (sponsor versus nonsponsor versus none) and sponsor text disclosure (present versus absent) conditions did not affect parents’ conceptual persuasion knowledge of the unboxing video. However, if a sponsor pre-roll ad was included, parents reported higher levels of sponsorship transparency of the unboxing video compared to parents who saw no pre-roll ad or a nonsponsor pre-roll ad. There was no additional effect on sponsorship transparency or conceptual persuasion knowledge when a sponsor text disclosure was included. Moreover, high levels of parental mediation conditionally impacted the indirect effect of a sponsor pre-roll advertisement via sponsorship transparency on perceptions of the unboxing video and attitudes toward the sponsor.
The conclusion section follows which emphasizes the implications for both society and what regulators can do to prevent some of the dangers associated with the influence of children. They make recommendations on future research in subsequent sections on influencer marketing strategies, the impact of influencer marketing on minor audiences, empowering children, and protecting children.
A number of societal and policy implications arise from the findings of prior research discussed above. More specifically, they may be important for policy aimed at protecting children’s interests. Most prior research focused on children’s exposure to and perception of influencer marketing. The above studies show that children spend a lot of time watching videos of their favorite influencers, in which they also encounter influencer marketing practices (e.g., Marsh, 2016; Folkvord et al., 2019; Martínez and Olsson, 2019). Moreover, they are also influenced by the content these influencers post and susceptible to the commercial messages incorporated in it (e.g., Folkvord et al., 2019; Martínez and Olsson, 2019), specifically those on (unhealthy) foods and beverages (e.g., De Jans et al., 2019;Coates et al., 2019a,b). Considering children’s susceptibility toinfluencer marketing practices, the findings of the above discussed prior research support the importance of existing guidelines and regulations stressing the fact that advertising should be recognizable as such, in particular for minor audiences. Two studies (De Jans et al., 2019; Coates et al., 2019b) tested the impact of an advertising disclosure on minors’ recognition of and susceptibility to influencer marketing. While both studies have shown that the inclusion of an advertising disclosure helps children recognize advertising, the study of Coates et al. (2019b) found that this increased recognition actually increased the effectiveness of influencer marketing, resulting in a higher intake of the promoted snack. Moreover, De Jans et al. (2019) found that the inclusion of an advertising disclosure may have positive effects on the influencer and subsequently on advertising effectiveness when minors were informed about advertising through an advertising literacy intervention in the format of an informational vlog. These studies suggest that a disclosure indeed helps children recognize influencer marketing practices as advertising and thus protects children from subconscious persuasion, without necessarily having a negative impact on the influencer and advertising effectiveness. In addition, Evans et al. (2018) found that sponsorship transparency in child-directed content is also appreciated by parents and has a positive effect on parents’ perceptions of unboxing videos, attitude toward the brand, and attitude toward the sponsor.
Literature review as part of a full paper
The following section is a dissection of an actual literature review which was crafted as part of an article entitled “The Halloween indicator is more a treat than a trick” which was published in the Journal of Accounting and Finance (2017). For context, this article was a research piece on the “Halloween indicator” which is a stock market phenomenon whereby investing slow down in the summer and pick up in the fall (right around Halloween). The authors conducted a quantitative analysis of the Halloween indicator in the aftermath of the 2008 financial crisis.
We will dissect each section and call out the progression of the literature review – beginning with seminal works and following the nuances, debates, controversies, modern understandings, and most importantly, how the empirical research study being conducted adds to the body of knowledge (remember, we are making an ever so slight bump on the edge of the sphere of knowledge). It is only after identifying the shoulders of giants, and the gaps in understanding that authors can make the case for why their research is important and relevant. Excerpts of the article’s literature review with annotations are captured here.
The literature review section of this article begins:
The seminal work of Bouman and Jacobsen (2002) spurred a debate in the literature regarding stock market efficiency, and extended the research on a growing body of literature on calendar anomalies in general.
The authors tip their hat to a seminal work, that of Bouman and Jacobsen (2002) who conducted an exhaustive study on the Halloween indicator. They are widely recognized as being the first major review of the issue and are considered a veritable seminal work. Their work spurs investigation not only into the summer-fall calendar anomaly in stock markets, but other seasonal anomalies as well.
Most prominent among these recognized calendar anomalies is the January effect, whereby stocks tend to rally in the first month of the year. The January effect has been found to exist in continental Europe markets (Canestrelli and Ziemba, 2000), the United Kingdom (Arsad and Coutts, 1997), Australia (Officer, 1975), Japan (Ziemba, 1991), and Thailand (Holden, Thompson, & Ruangrit, 2005). Additional calendar anomalies include the Monday effect, turn-of-the-month effect, and the holiday effect.
Because Bouman and Jacobsen (2002) started a dialogue on a bevy of other anomalies, the authors briefly mention them here. What this does is provide background on Halloween indicator as one of many other seasonal anomalies.
Andrade, Chhaochharia and Fuerst (2013) present two challenges to these market trends in that they are difficult to trade around given the significant transaction costs associated with trying to capture these arbitrage opportunities, and that in most cases the market opportunities have dissipated since each of these has been identified.
After identifying and articulating the existence of calendar anomalies, some scholars began to explore the practical implications, and add to the scholarly discussion by bridging theory and practice.
In response to the findings presented by Bouman and Jacobsen’s (2002), Jacobsen and Visaltanachoti (2009) re-evaluate Halloween indicator in terms of specific U.S. sectors and industries. They find that the Halloween indicator differs across 17 sectors and 49 industries. Specifically, the effect was “almost absent in sectors and industries related to consumer consumption but in production sectors and industries” (p. 439).
As scholars continue to uncover the facets of a particular research string, they can sometimes disagree, or find differences in new contexts. The authors of the article include this (mini) controversy here.
Jacobsen and Zhang (2012) conduct the most comprehensive research study on the subject to include all available years in all countries for which data was available. They analyze more than 300 years of market information, and show that the Halloween indicator can be observed over the previous three centuries. Investors utilizing the “sell in May and go away” strategy during this period would have beaten the buy-and-hold strategy by more than 80% of the time.
Once there is enough dialogue on an issue in the literature, some scholars begin to see how far back the idea originated, or can be traced. Notice here that Jacobsen, a seminal author, is conducting a more comprehensive look at the Halloween indicator. This work of Jacobsen and Zhang (2002) followed stock market occurrences of the Halloween indicator dating back all the way to the 18th century London stock market.
Andrade, Chhaochharia, and Fuerst (2013) validate the existence of the Halloween indicator. They find that not only can the Halloween indicator still be observed in the stock market, but that trading strategies could be employed to capture the effect in foreign currency valuations, credit markets, and volatility risk premiums. Despite the strong evidence presented by Bouman and Jacobsen (2002), Jacobsen and Zhang (2012), and Andrade, Chhaochharia, and Fuerst (2013), several scholars have postulated alternative explanations for the Halloween indicator. Most notably, Lucey and Zhao (2008) present contradictory evidence that attributes the difference in the two halves of the year to the January effect. Bouman and Jacobsen (2002) remove January from their data set and the results “reject the hypothesis that the [Halloween indicator] is the January effect in disguise” (p.1627). Jacobsen and Zhang (2012) identify the January effect as a regular occurrence beginning in 1830, but this anomaly alone does not explain the November through April return premiums. Some argue that the Halloween effect is a result of data mining (Maberly & Pierce, 2004). In response to the data mining claim, Jacobsen and Zhang (2012) analyze the entire available data set spanning 300 years and their results refute the notion that the Halloween effect is a data-driven result. They show that the anomaly exists in markets across the globe in both developed and emerging markets and has remained consistent over time. Another possible explanation for the Halloween indicator anomaly is that November through April has a higher risk profile that naturally leads to a higher return. Bouman and Jacobsen (2002) show that risk, as measured by standard deviation, is actually higher in May-October than in November-April period for most countries in their sample. A final explanation for the Halloween indicator is that during the summer months, investors take more vacation and this affects their trading strategy.
Alas we have a full-fledged debate in the academic literature as scholars attempt to explain the causes, whether it actually exists, and more practical implications. As research trains mature and develop, there will be more disagreements, new developments, and in many cases consensus of an idea or thought once enough studies confirm it. The purpose of the literature review should explore all of these controversies, confirmatory studies, and variances so that the importance of the study currently conducted can be seen as relevant and an addition to the academic debate on the issue.
This paper revisits the Halloween effect and investigates whether this anomaly can still be observed during and after the 2008 financial crisis. Given the extreme impact of the 2008 financial crisis, it would be interesting to study if the Halloween effect has survived or diminished in the fallout. It is extremely difficult and costly to identify a winning trading strategy in current stock market environment, especially during a bear market. This paper contributes to the literature in several different ways. First, we examine the existence of the Halloween effect during and after the most recent global financial crisis. Second, we propose an aggressive trading strategy that exploits the underperformance of the stock market in summer months. Third, this paper offers a new explanation of the Halloween indicator anomaly.
Finally, the authors make their case for why and how the study they are conducting advances knowledge on the issue. Notice that research articles can advance understanding in more than one way at a time. This study investigates the issue after a major crisis to see if it still exists, then provides a practice recommendation, and finally explains the origins of the phenomenon.