Introduction
Adolescence denotes the maturational period that commences with the onset of puberty and ends with the establishment of an independent, adult role in society (Crone & Dahl, Reference Crone and Dahl2012; Blakemore & Mills, Reference Blakemore and Mills2014; Steinberg, Reference Steinberg2014). Often defined by its age range (which is thought to extend from age nine or ten through the early twenties; Pringle et al., Reference Pringle, Mills, McAteer, Jepson, Hogg, Anand and Blakemore2016), adolescence represents a sensitive developmental period for learning about and adopting a wide range of health behaviors. The physical, neural, psychological and social changes that begin with puberty contribute to skill learning, exploring novel environments and risk-taking behaviors. Risk-taking during adolescence can promote positive outcomes, such as developing and engaging in new intellectual and artistic ideas, forging new social relationships and becoming increasingly involved in one's community (for a recent review, see Telzer, Reference Telzer2016), as well as negative outcomes, including increased tobacco and drug use (Warren et al., Reference Warren, Riley, Asma, Eriksen, Green, Blanton, Loo, Batchelor and Yach2000; Dahl, Reference Dahl2004; Grant et al., Reference Grant, Dawson, Stinson, Chou, Dufour and Pickering2004), risky driving (Williams, Reference Williams2003; Simons-Morton et al., Reference Simons-Morton, Lerner and Singer2005) and criminal behavior (Zimring, Reference Zimring1998).
Adolescence is a critical period for establishing behavioral patterns (Jessor, Reference Jessor1984). Behaviors established during adolescence, from health-promoting habits such as engaging in physical activity and healthy eating to health-harming behaviors like smoking and drinking, are likely to continue throughout life and have a long-lasting influence on individuals’ health and well-being (Kleinert, Reference Kleinert2007). From an anthropological perspective, the increased tendency for risk-taking during adolescence is functionally adaptive, as this tendency facilitates the exploration of new social roles, the creation of meaningful relationships, and engagement in other rewarding experiences (Ellis et al., Reference Ellis, Del Giudice, Dishion, Figueredo, Gray, Griskevicius, Hawley, Jake Jacobs, James, Volk and Wilson2012). Nevertheless, adolescents’ vulnerability to engaging in harmful risks can lead to negative social and behavioral trajectories. The potential long-term influence of these behaviors underscores the importance of enhancing opportunities for positive, pro-social risk-taking and decreasing engagement in harmful behaviors during this developmental period.
Public health professionals have long recognized the importance of preventing the adoption of unhealthy behaviors during adolescence and have approached this issue, in part, through media campaigns. Mass media health campaigns have been effective health promotion tools for delivering health messages to large groups of people (Hornik, Reference Hornik2002), targeting adolescent health behaviors including smoking initiation (Farrelly et al., Reference Farrelly, Niederdeppe and Yarsevich2003; Wakefield et al., Reference Wakefield, Flay, Nichter and Giovino2003; Farrelly et al., Reference Farrelly, Davis, Haviland, Messeri and Healton2005), risky sexual behavior (Zimmerman et al., Reference Zimmerman, Donohew, Palmgreen, Noar, Cupp and Floyd2011) and marijuana use (Palmgreen et al., Reference Palmgreen, Lorch, Stephenson, Hoyle and Donohew2007). The success of health messages relies critically on an understanding of the psychological processes that underlie persuasion and the various social, environmental and developmental factors that may influence this process. Yet, adolescents’ exposure to campaign messages does not always produce the intended outcomes (Noar, Reference Noar2006; Brennan et al., Reference Brennan, Momjian, Jeong, Naugle, Parvanta and Hornik2012; Aubrey et al., Reference Aubrey, Behm-Morawitz and Kim2014; for a review, see Noar, Reference Noar2006), suggesting the need for additional variables that can predict message effectiveness.
In the past decade, empirical studies have provided evidence that neuroimaging methods may add additional value to the design and selection of health messages and interventions. Brain signals collected during health message exposure in small groups of people have been found to predict message success at both the individual and population levels and help illuminate the underlying cognitive mechanisms that may lead to persuasion (Falk et al., Reference Falk, Berkman, Mann, Harrison and Lieberman2010; Chua et al., Reference Chua, Ho, Jasinska, Polk, Welsh, Liberzon and Strecher2011; Falk et al., Reference Falk, Berkman, Whalen and Lieberman2011; Falk et al., Reference Falk, Berkman and Lieberman2012; Berkman & Falk, Reference Berkman and Falk2013; Wang et al., Reference Wang, Ruparel, Loughead, Strasser, Blady, Lynch, Romer, Cappella, Lerman and Langleben2013; Cooper et al., Reference Cooper, Tompson, Brook O'Donnell and Emily2015; Falk et al., Reference Falk, O'Donnell, Cascio, Tinney, Kang, Lieberman, Taylor, An, Resnicow and Strecher2015; Wang et al., Reference Wang, Lowen, Romer, Giorno and Langleben2015; Weber et al., Reference Weber, Huskey, Mangus, Westcott-Baker and Turner2015; Falk et al., Reference Falk, O'Donnell, Tompson, Gonzalez, Dal Cin, Strecher, Cummings and An2016; Cooper et al., Reference Cooper, Bassett and Falk2017). Across these studies, neural activation in the ventromedial prefrontal cortex (VMPFC) during exposure to health messages has consistently been linked to health behavior change. It has been theorized that neural response in VMPFC during health message exposure signals the assessment of the value of the health message to oneself (Cooper et al., Reference Cooper, Tompson, Brook O'Donnell and Emily2015; Falk et al., Reference Falk, O'Donnell, Cascio, Tinney, Kang, Lieberman, Taylor, An, Resnicow and Strecher2015) or the integration of the message's value with one's self-concept (Vezich et al., Reference Vezich, Katzman, Ames, Falk and Lieberman2017). However, the brain's value system undergoes considerable changes during adolescence, influenced by developments in cognitive control and social cognition systems. These developmental considerations may shape the way in which findings from adult studies can be applied to adolescents.
Despite a growing body of literature in social and communication neuroscience, scant research has examined the role of the brain in adolescent health persuasion. Considering that the brain undergoes significant development during puberty and adolescence, the extent to which insights from adult neuroscience studies of persuasion and social influence can be applied to adolescents remains an open question. Combining empirical evidence from the neuroscience of persuasion and the neurodevelopment of the value system during adolescence, we highlight potential opportunities to integrate insights about the adolescent brain in designing messages that channel adolescents’ motivations toward pro-health behaviors and creating messages that maximally harness the power of social media.
Adolescent health behavior and media health campaigns
Adolescence is a dynamic developmental period. The hormonal changes that stimulate adolescent pubertal maturation are accompanied by complex physical, social and emotional changes (Steinberg & Morris, Reference Steinberg and Morris2001; Crone & Dahl, Reference Crone and Dahl2012). As noted above, these changes are associated with increased risk-taking, which in turn can produce preventable injury and death. According to a 2010 report by the Centers for Disease Control and Prevention (Miniño, Reference Miniño2010), the top three causes of death during adolescence are accidents (most of which are caused by motor vehicle crashes), homicide, and suicide. To reduce the initiation and prevalence of harmful and potentially life-threatening behaviors in adolescents, considerable resources have been invested in health promotion interventions, including health-focused mass media campaigns. Mass media health campaign messages, which range in format from professionally developed public service announcements (PSAs) to entertainment education programs (e.g., TV shows with health messages embedded in the storylines), are disseminated through an array of media platforms, including television, radio and newspapers. These platforms are effective tools for broadcasting health messages to large populations (Noar, Reference Noar2006). The success of these campaigns is contingent on the content of the messages and audience members’ exposure to these messages during routine media use (Wakefield et al., Reference Wakefield, Loken and Hornik2010) and is facilitated by social interactions surrounding the messages (Brennan et al., Reference Brennan, Durkin, Wakefield and Kashima2016).
To this end, media campaigns can achieve intended cognitive and/or behavioral outcomes through direct and indirect pathways (Wakefield et al., Reference Wakefield, Loken and Hornik2010). Many campaigns aim to directly affect individuals by invoking cognitive or emotional responses through direct exposure to campaign messages. For instance, a campaign aimed to prevent smoking onset may highlight specific risks of smoking in campaign messages, with the expectation that individual exposure to these messages will influence adolescents to espouse increased anti-smoking beliefs. Complementary to this approach, campaigns can also achieve intended outcomes through indirect pathways, such as interpersonal communication about campaign messages (Katz & Lazarsfeld, Reference Katz and Lazarsfeld1955; Katz, Reference Katz1957). For example, exposure to messages can prompt individuals to discuss the content of messages with peers, resulting in downstream effects on peers’ normative beliefs or behaviors consistent with message content (Brennan et al., Reference Brennan, Momjian, Jeong, Naugle, Parvanta and Hornik2012). More broadly, health campaigns can prompt changes in public policy at the institutional level by promoting public discussions of the issue (e.g., policy restrictions on the age of tobacco purchase influencing tobacco use), thereby influencing individual behavior (McCombs & Shaw, Reference McCombs and Shaw1972; Goldberg et al., Reference Goldberg, Fishbein and Middlestadt1997; Hornik, Reference Hornik2002; Hornik & Yanovitzky, Reference Hornik and Yanovitzky2003). The direct and indirect pathways of influence highlight the importance of optimizing campaigns with respect to at least two sets of campaign outcomes: (1) changes in health-related cognitions and behaviors that result from direct campaign exposure; and (2) the extent to which individuals share and positively discuss campaign messages with others.
Indirect pathways to campaign effects (e.g., interpersonal sharing and influence) may be amplified by the new media environment. There has been immense growth in adolescent engagement in media activities and use of media devices in recent years (Jordan & Romer, Reference Jordan and Romer2014; Lenhart, Reference Lenhart2015; Rideout, Reference Rideout2016). With its rapid increase in popularity, particularly among adolescents, social media is a promising avenue for the dissemination of health campaign messages targeting adolescents. According to a 2015 report from the Pew Research Center, 92% of adolescents aged 13–17 use the internet daily, and the majority of them (71%) use more than one social media platform (Lenhart, Reference Lenhart2015). Campaigns targeting adolescents, such as ‘truth’ and ‘The Real Cost’ anti-smoking campaigns, increasingly incorporate new media channels into their campaign strategies in addition to conventional media outlets, disseminating campaign messages online through social media platforms such as Facebook and Instagram. This type of media platform provides unique functions (i.e., online sharing and commenting) that may increase campaign reach and engagement (Korda & Itani, Reference Korda and Itani2013; Rus & Cameron, Reference Rus and Cameron2016). More broadly, online components in a campaign may improve the efficacy of campaign messages, though it should be noted that these functions can also undermine campaign effectiveness if not channeled properly (Geber et al., Reference Geber, Baumann and Klimmt2017).
In sum, mass media and social media have strong potential to influence adolescent behavioral trajectories. Below, we argue that neuroscience studies of persuasion can complement existing campaign evaluation studies and laboratory studies of message effects by providing additional information about the mechanisms through which messages influence cognitions and behavior. We then review key ways in which adolescent brains differ from adult brains and suggest ways in which this may impact the optimal design of research and interventions at this intersection.
Neuroscience studies of persuasion in adults
Current approaches to health intervention design and the prediction of health behaviors make strong use of self-report measures both by asking people to directly evaluate campaign messages (Atkin & Freimuth, Reference Atkin and Freimuth2001) and by manipulating message features and then measuring people's self-reports of the cognitions that follow (Cappella, Reference Cappella2006). For example, campaign developers often recruit members of the campaign's target audience to rate the effectiveness of campaign advertisements during the message testing phase of development or report the frequency of their exposure to campaign ads as part of a formal evaluation (Atkin & Freimuth, Reference Atkin and Freimuth2001). Other approaches include systematically varying features of health messages, such as message content and form, and subsequently measuring people's behavioral and cognitive reactions to the manipulated features (Cappella, Reference Cappella2006). Neuroimaging tools can complement both of these types of designs by providing insight into the real-time underlying mental processes that occur during message exposure without the need for participant introspection or retrospection about the processes elicited by messages, thereby circumventing some potential biases (Paulhus, Reference Paulhus, Angleitner and Wiggins1986; Fazio & Olson, Reference Fazio and Olson2003; Dijksterhuis, Reference Dijksterhuis2004) introduced by self-report measures (Lieberman, Reference Lieberman2010). Neuroimaging refers to a broad set of techniques for measuring brain activity, such as functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy and electroencephalography, among others. fMRI, which uses changes in blood flow in the brain as an indicator of neural activity, is among the neuroimaging methods most commonly used to study health persuasion.
In the last decade, a growing number of studies have demonstrated that neural signals during exposure to health messages can predict key campaign outcomes including behavior change and message sharing. These studies generally adopt a ‘brain-as-predictor’ approach (Berkman & Falk, Reference Berkman and Falk2013), which uses signals in brain systems previously implicated in psychological processes to predict cognitive and behavioral outcomes. Brain response during health message exposure has been shown to predict individual-level health behaviors such as changes in smoking-relevant behaviors (Chua et al., Reference Chua, Ho, Jasinska, Polk, Welsh, Liberzon and Strecher2011; Falk et al., Reference Falk, Berkman, Whalen and Lieberman2011; Wang et al., Reference Wang, Ruparel, Loughead, Strasser, Blady, Lynch, Romer, Cappella, Lerman and Langleben2013; Riddle et al., Reference Riddle, Newman-Norlund, Baer and Thrasher2016; Owens et al., Reference Owens, MacKillop, Gray, Hawkshead, Murphy and Sweet2017), sunscreen use (Falk et al., Reference Falk, Berkman, Mann, Harrison and Lieberman2010; Vezich et al., Reference Vezich, Katzman, Ames, Falk and Lieberman2017) and physical activity (Falk et al., Reference Falk, O'Donnell, Cascio, Tinney, Kang, Lieberman, Taylor, An, Resnicow and Strecher2015). Consistent evidence suggests that neural activity in the medial prefrontal cortex (MPFC) can predict message-consistent behaviors, although the specific subregions of the MPFC vary across studies, with some studies reporting dorsal subregions of MPFC, and some reporting more ventral subregions of MPFC (VMPFC) (for reviews, see Cacioppo et al., Reference Cacioppo, Cacioppo and Petty2016; Falk & Scholz, Reference Falk and Scholz2018). Within this body of work, several studies have shown that brain responses to persuasive health messages can account for variance in health outcomes above and beyond self-report measures (Falk et al., Reference Falk, Berkman, Mann, Harrison and Lieberman2010; Falk et al., Reference Falk, Berkman, Whalen and Lieberman2011; Riddle et al., Reference Riddle, Newman-Norlund, Baer and Thrasher2016). In one study (Falk et al., Reference Falk, Berkman, Whalen and Lieberman2011), smokers were shown a series of anti-smoking ads during an fMRI scan. Following each ad, participants rated the extent to which the ad made them feel a sense of self-efficacy regarding quitting smoking, their intention to quit and the self-relevance of the ad. Exhaled carbon monoxide (CO), a biological indicator of smoke exposure, was measured before and one month after the scanning session. Neural activation in the VMPFC during ad exposure was a significant predictor of changes in expired CO levels, controlling for self-reported intentions to quit, self-efficacy to quit and self-relevance of the ads. The authors found that VMPFC neural activity on average predicted 23% of the variance in smoking behavior change on top of the variance predicted by self-reported attitudes and intentions. A follow-up study that compared model fit between models using self-reported predictors and models using self-report and neural measures reported similar figures ranging from 14% to 32% (Tables 5–7 from Riddle et al., Reference Riddle, Newman-Norlund, Baer and Thrasher2016), depending on the characteristics of the stimuli and participants. It is worth noting that the number of relevant studies is still small and that future studies that examine the conditions under which neural measures provide additional predictive power compared to self-report or behavioral measures will be useful.
A related brain-as-predictor approach has been used to predict population-level message-induced behavior change (Falk et al., Reference Falk, Cascio, O'Donnell, Carp, Tinney, Bingham, Shope, Ouimet, Pradhan and Simons-Morton2014; Falk et al., Reference Falk, O'Donnell, Tompson, Gonzalez, Dal Cin, Strecher, Cummings and An2016). This approach traverses different levels of analysis in that neural activity in a small group of individuals is used to forecast population-level message success. For instance, neural activation within the VMPFC, a brain region thought to underlie the computation of the value for the self, in small samples of smokers predicted real-world success of smoking cessation messages at the population level (Falk et al., Reference Falk, Berkman and Lieberman2012; Falk et al., Reference Falk, O'Donnell, Tompson, Gonzalez, Dal Cin, Strecher, Cummings and An2016). This approach has also been employed to predict the population-level success of cultural phenomena, such as song downloads (Berns & Moore, Reference Berns and Moore2012), microloans raised (Genevsky & Knutson, Reference Genevsky and Knutson2015) and the success of movies (Boksem & Smidts, Reference Boksem and Smidts2014). These initial studies demonstrate that neural signals in the brain's valuation system (VMPFC and ventral striatum [VS]) during exposure to a wide range of stimuli can reflect population-level preferences related to those stimuli. However, the underlying mechanisms that explain these relationships, as well as the boundary conditions under which neural responses do and do not reflect population-level outcomes, have not yet been fully examined.
In addition to predicting direct effects on health behavior change, neural responses to messages can also predict whether people share campaign-relevant information. In this respect, neural responses to messages may also help forecast indirect campaign effects such as what information is likely to spread from person to person. Recent studies have linked neural activity within positive valuation, self-related processing, and social cognition regions during exposure to health-related news items with both individual-level intention to share the news articles (Baek et al., Reference Baek, Scholz, O'Donnell and Falk2017) and total number of shares at the population level (Scholz et al., Reference Scholz, Baek, O'Donnell, Kim, Cappella and Falk2017). The authors demonstrated that neural activity in the brain's self-relevance processing and social cognition networks increases brain activity in the value system, which in turn predicts population-level article virality. This suggests that messages that are more personally relevant for the individual (e.g., mentioning issues that one deeply cares about) or messages that induce more thoughts about social consequences of sharing and/or other people's mental states (e.g., containing information that is considered useful for the individual's friends) may lead to greater perceived value of sharing and are thus more likely to be shared. Together, these studies highlight the importance of self-relevant and social cognitions when individuals consider the value of sharing health messages, demonstrating that neural signals in the value system in a small group of people can predict population-level popularity.
Given the accumulating findings that link VMPFC neural activity and message-relevant outcomes, several hypotheses have been proposed to account for why VMPFC activity may be linked to behavior change and message sharing. One hypothesis is that brain signals in the value system indicate an individual's overall computed value of a message to oneself (Cooper et al., Reference Cooper, Tompson, Brook O'Donnell and Emily2015; Falk et al., Reference Falk, O'Donnell, Cascio, Tinney, Kang, Lieberman, Taylor, An, Resnicow and Strecher2015; Vezich et al., Reference Vezich, Katzman, Ames, Falk and Lieberman2017). This idea was further developed into a valuation model of influence and message sharing (Falk & Scholz, Reference Falk and Scholz2018), proposing that a common pathway of subjective value maximization underlies people's decisions about sharing information or being influenced by a message. Health messages that engage greater responses in the brain's valuation regions are thought to elicit more thoughts about personal value and are therefore more successful at changing individual health behaviors and being shared with others. This account links social science research on persuasion (Cialdini & Goldstein, Reference Cialdini and Goldstein2004; Berger, Reference Berger2014; Albarracin & Shavitt, Reference Albarracin and Shavitt2018) with the neuroeconomic decision-making model (Levy & Glimcher, Reference Levy and Glimcher2012), which states that activity in the VMPFC and VS is key in computing the subjective value of a wide range of stimuli (Levy & Glimcher, Reference Levy and Glimcher2012; Bartra et al., Reference Bartra, McGuire and Kable2013). The valuation model is echoed in prominent theories of behavior change (Fishbein & Ajzen, Reference Fishbein and Ajzen2011), according to which individuals weigh different considerations relevant to a behavior (such as their behavioral beliefs or self-efficacy) when assessing the value of engaging in the behavior, and it expands prior theories by highlighting the significance of self- and social-related inputs.
In sum, studies from social and communication neuroscience demonstrate that neural activity can serve as a significant predictor of health behavior outcomes and health message sharing at both individual and population levels. Current theory suggests that VMPFC and VS activity during message exposure may be an indicator of a valuation process in which one weighs a message's value against one's self-concept and social relevance, and that brain responses in these regions are important predictors of outcomes across a range of studies. There is currently less research on the neural mechanisms underlying persuasion in adolescents, and the extent to which insights learned from adult persuasion research can be extended to adolescents is unclear. Next, we discuss a core set of neural changes in adolescents that are relevant to these questions, with particular emphasis on the value system.
Developmental changes in brain systems underlying decision-making
A substantial body of research in developmental neuroscience has laid the groundwork for understanding the normative neurodevelopmental changes that underlie adolescent decision-making. In general, at least two sets of maturational processes influence adolescent decision-makingFootnote 1: (1) increased reward sensitivity in the valuation system, along with increased salience for social and affective influences; and (2) a gradual strengthening of cognitive control, self-inhibition and the ability to align behavior with long-term goals (Suleiman & Dahl, Reference Suleiman and Dahl2017). The first of these processes is thought to underlie changes in motivation and increased sensitivity to certain types of learning experiences – especially those associated with social relationships. Compared to the second set of processes, which are less dependent on pubertal maturation (Dahl, Reference Dahl2004), the increase in reward sensitivity and social saliency occurs relatively abruptly and is more directly linked with puberty (Braams et al., Reference Braams, van Duijvenvoorde, Peper and Crone2015).
Reward and value processing are associated with activation in similar brain regions in adolescents and adults, including the VMPFC and the VS. These regions are responsive to primary rewards such as food and sex, as well as more abstract forms of rewards such as the well-being of others and smiling faces (Bjork et al., Reference Bjork, Knutson, Fong, Caggiano, Bennett and Hommer2004; May et al., Reference May, Delgado, Dahl, Stenger, Ryan, Fiez and Carter2004; Ernst et al., Reference Ernst, Nelson, Jazbec, McClure, Monk, Leibenluft, Blair and Pine2005; Galvan et al., Reference Galvan, Hare, Parra, Penn, Voss, Glover and Casey2006; Eshel et al., Reference Eshel, Nelson, Blair, Pine and Ernst2007). There is general agreement that adolescents tend to show higher VS activation during reward anticipation compared to children and adults (Christakou et al., Reference Christakou, Brammer and Rubia2011; Padmanabhan et al., Reference Padmanabhan, Geier, Ordaz, Teslovich and Luna2011; Galván & McGlennen, Reference Galván and McGlennen2013; Barkley-Levenson & Galván, Reference Barkley-Levenson and Galván2014).Footnote 2 Increased activation in the VS in response to immediate monetary rewards during adolescence has been associated with engagement in harmful behaviors, including alcohol abuse, smoking, dysfunctional eating, and drug addiction (Loxton & Dawe, Reference Loxton and Dawe2001; Kambouropoulos & Staiger, Reference Kambouropoulos and Staiger2004; O'Connor & Colder, Reference O'Connor and Colder2005; Crews et al., Reference Crews, He and Hodge2007; Goudriaan et al., Reference Goudriaan, Oosterlaan, Beurs and Brink2008; Peeters et al., Reference Peeters, Oldehinkel and Vollebergh2017). However, studies also suggest that heightened sensitivity to reward in the VS can enhance development by increasing motivation in positive types of learning (Cohen et al., Reference Cohen, Asarnow, Sabb, Bilder, Bookheimer, Knowlton and Poldrack2010; van den Bos et al., Reference van den Bos, Cohen, Kahnt and Crone2012; Davidow et al., Reference Davidow, Foerde, Galván and Shohamy2016; Gerraty et al., Reference Gerraty, Davidow, Foerde, Galvan, Bassett and Shohamy2017). More recent research that examines reward sensitivity in contexts other than direct monetary rewards suggests that heightened sensitivity to other types of reward (e.g., donation to the participant's family, redeemable game points) predicts declines in depressive symptoms (Telzer et al., Reference Telzer, Fuligni, Lieberman and Galván2014) and improved cognitive performance (Geier & Luna, Reference Geier and Luna2012). Increased reward sensitivity is likely part of the normative, adaptive developmental process that motivates adolescents to engage in behaviors that support the successful transition to adulthood (Spielberg et al., Reference Spielberg, Olino, Forbes and Dahl2014). In sum, heightened sensitivity in the value system signals both positive and negative outcomes, depending on the context and the type of reward and social context.
In addition to a general heightened sensitivity during adolescents, value computation that integrates choices with multiple attributes is thought to also develop during adolescence. Decisions are often made among options that differ along multiple attributes, requiring computation and integration of distinct value signals (Montague & Berns, Reference Montague and Berns2002; Rangel et al., Reference Rangel, Camerer and Montague2008). Neuroimaging studies have consistently shown that integrated subjective value signals are encoded in the VMPFC (Hare et al., Reference Hare, Camerer and Rangel2009; Bartra et al., Reference Bartra, McGuire and Kable2013). A number of studies have examined how neural computation of value differs across development in the context of food choice (Lim et al., Reference Lim, Cherry, Davis, Balakrishnan, Ha, Bruce and Bruce2016; van Meer et al., Reference van Meer, van der Laan, Viergever, Adan and Smeets2017). For instance, a recent study compared neural responses to healthy and unhealthy food stimuli between early adolescents (10–12 years old) and adults (32–52 years old) (van Meer et al., Reference van Meer, van der Laan, Viergever, Adan and Smeets2017). The results of this study suggest that although both early adolescent and adult VMPFC activations were modulated by the tastiness of the food, only adult VMPFC activation was modulated by healthiness. These results indicate that when making decisions that include multiple attributes, adolescents may show distinct neural value computation compared to adults, influencing downstream decision-making.
Reward and value processing in the VMPFC and VS are not the exclusive determinants of adolescent decision-making. Other brain systems, including those involved in cognitive control and social cognition, are believed to be involved in valuation and decision-making processes (Steinberg, Reference Steinberg2004; Geier & Luna, Reference Geier and Luna2009). Cognitive control refers to the ability to flexibly and adaptively coordinate behavior to achieve internal goals and includes a variety of interacting components, such as working memory, attention allocation and response inhibition (Badre, Reference Badre2011; Luna et al., Reference Luna, Marek, Larsen, Tervo-Clemmens and Chahal2015). Adolescents’ heightened reward sensitivity may be partially explained by the relatively slower maturation of cognitive control systems compared to the VS (Casey et al., Reference Casey, Jones and Hare2008; Sturman & Moghaddam, Reference Sturman and Moghaddam2011; Pfeifer & Allen, Reference Pfeifer and Allen2012). A study comparing children, adolescents and young adults’ neural responses to risky decision-making found that, compared to adolescents, adults relied more on the prefrontal cortex (PFC), a set of brain regions implicated in executive and deliberative processing, when making risky choices (Eshel et al., Reference Eshel, Nelson, Blair, Pine and Ernst2007). Other research that explored the functional connectivity between brain regions showed decreased connectivity between the VS and VMPFC and increased connectivity between the lateral PFC and VS across adolescence (van Duijvenvoorde et al., Reference van Duijvenvoorde, Peters, Braams and Crone2016), suggesting that the adolescent valuation system is increasingly influenced by the lateral PFC, a brain region thought to index cognitive control (Wagner et al., Reference Wagner, Maril, Bjork and Schacter2001). Hence, the changes in connectivity between the cognitive control and motivational systems and shifts in activation of these systems when processing rewards contribute to developmental changes in behavior.
Adolescence is marked by increased neural sensitivity to social cues (Crone & Dahl, Reference Crone and Dahl2012), resulting in a more pronounced influence of social factors on behavior. This neural development is considered adaptive, as adolescents begin to spend more time with peers, navigate social relationships without parental support and develop social skills that are important for adulthood (Blakemore & Mills, Reference Blakemore and Mills2014). Subjective valuation during adolescence shows heightened sensitivity to social influence compared to children and adults. In one study that examined the influence of peers on valuation processing in adolescents (ages 14–19) and adults (ages 25–35), participants were instructed to perform a reward processing task both alone and with same-sex, same-aged peers (Smith et al., Reference Smith, Steinberg, Strang and Chein2015). The reward processing task required participants to make a series of guesses about the number on a card, and each correct guess was followed by a reward cue. Compared to adults, adolescent VS neural activity increased more with peer presence, suggesting that adolescent VS activity to reward is more sensitive to peer observation. In addition, studies of reward processing that incorporate more explicit social information, such as social norms, suggest that social information can influence adolescent behavior by modulating neural signals related to value processing (Sherman et al., Reference Sherman, Payton, Hernandez, Greenfield and Dapretto2016; Welborn et al., Reference Welborn, Lieberman, Goldenberg, Fuligni, Galvan and Telzer2016). Behaviorally, adolescents are more likely to conform to the perceived social norms of their peers compared to adults (for a review, see Chein, Reference Chein2015). Neuroimaging studies in this area demonstrate that peer contexts affect adolescent decision-making by influencing brain regions associated with social and value processing (Chein et al., Reference Chein, Albert, O'Brien, Uckert and Steinberg2011; Peake et al., Reference Peake, Dishion, Stormshak, Moore and Pfeifer2013; Cascio et al., Reference Cascio, O'Donnell, Bayer, Tinney and Falk2015). In sum, the adolescent value system is more sensitive to both implicit social cues and explicit normative social information compared to adults.
Taken together, findings from these studies suggest that the neural valuation system undergoes significant functional specialization and may result in increased reward sensitivity during this developmental period. Moreover, the adolescent valuation system is dependent on social context and is increasingly influenced by the still maturing cognitive control system. It is important to acknowledge that brain maturation does not occur independent of other factors. Instead, learning and experiences during adolescence shape developing neural networks in important ways (Takesian & Hensch, Reference Takesian and Hensch2013). Nevertheless, these neurodevelopmental changes may serve as neural underpinnings for the observed behavioral traits in adolescents, including the motivation to seek novel, exciting and high-sensation experiences. Considering adolescence as an important time period of exploration and learning, these neurodevelopmental changes are considered critical to supporting healthy psychosocial development during adolescence. For example, this neural development may be necessary in supporting adolescents to step outside their comfort zone, learn a new sport or entertain alternative belief systems. In the next section, we discuss the implications of recent communication and developmental neuroimaging studies on adolescent media health campaigns and consider how neuroimaging tools may help improve adolescent health persuasion through media platforms.
Implications for adolescent media health promotion
Recent advances in social and communication neuroscience offer insights about the neural mechanisms that underlie adult health communication. Evidence suggests that neural activity in the brain's valuation system plays an important role in health persuasion outcomes, including behavior change and message sharing (Cooper et al., Reference Cooper, Tompson, Brook O'Donnell and Emily2015; Riddle et al., Reference Riddle, Newman-Norlund, Baer and Thrasher2016; Baek et al., Reference Baek, Scholz, O'Donnell and Falk2017; Cooper et al., Reference Cooper, Bassett and Falk2017; Scholz et al., Reference Scholz, Baek, O'Donnell, Kim, Cappella and Falk2017; Vezich et al., Reference Vezich, Katzman, Ames, Falk and Lieberman2017). Considering findings that highlight the changes in the valuation system over the course of adolescence, the extent to which insights from the adult persuasion neuroscience literature can be applied to adolescents is an open question. Combined findings from persuasion and developmental neuroscience underscore at least two possible ways that neuroscience can inform the promotion of health behavior in adolescents.
Explaining additional variance in adolescent health behavior
A direct application of neuroimaging methods to adolescent health promotion is that they could improve our ability to predict attitudes and behavior based on neural responses to health messaging. First, studies in adult populations demonstrate that neural signals during message exposure can predict individual- and population-level behavior change and often provide information that is different from complementary methods such as questionnaires, explaining up to an additional quarter of the variance in health-relevant outcomes compared to survey measures alone (Falk et al., Reference Falk, Berkman, Mann, Harrison and Lieberman2010; Falk et al., Reference Falk, Berkman, Whalen and Lieberman2011; Riddle et al., Reference Riddle, Newman-Norlund, Baer and Thrasher2016; for a review, see Falk & Scholz, Reference Falk and Scholz2018). Additionally, value-related neural activity in adults during message exposure is associated with the intention to share at the individual level as well as population-level message virality.
Some studies have begun to use neural activation to predict relevant outcomes of health campaign messages in adolescents. One study directly compared adolescents’ (15–19 years old) neural activation to strong (convincing) versus weak PSAs as rated by a group of independent raters. The findings demonstrated that stronger PSAs elicited significantly more activation in the lateral PFC, a brain region implicated in executive processing (Ramsay et al., Reference Ramsay, Yzer, Luciana, Vohs and MacDonald2013). The authors interpreted this result as indicative of a cognitive control process that translates the persuasive anti-drug message into internal goals. Another study examined adolescents’ neural responses to anti-smoking PSAs from a national smoking prevention campaign and found that increased brain activation in the VMPFC (a region of the brain involved in valuation) during message exposure was associated with the degree to which participants talked about the central theme of the message when they verbally shared their opinions on the ads (Pei et al., Reference Pei, Schmaelzle, O'Donnell, Kranzler and Falk2018). These studies provide initial support that the brain imaging paradigms used to study adult health persuasion can be applied to adolescents, even though the neural mechanisms that underlie persuasion may be different. Notably, neither study directly linked adolescent neural activity during health message exposure with behavior change. Future neuroimaging studies that include individual-level and population-level communication outcomes in adolescents will help us better understand the neuropsychological processes that underlie health persuasion and how they change with development and inform more effective campaign design.
Neuroimaging tools can also forecast message sharing, which is also integral for population-level health campaign success. In adults, neural activation in brain regions involved in self-relevance and social cognition contribute to the value of sharing a message (Baek et al., Reference Baek, Scholz, O'Donnell and Falk2017; Scholz et al., Reference Scholz, Baek, O'Donnell, Kim, Cappella and Falk2017). Future work in adolescent participants can help determine the extent to which neural signals in the same or additional regions can predict message sharing. These insights can inform the development of messages that are both effective and shareworthy, thus maximizing the reach and overall success of a campaign.
More broadly, the ability to predict behavior based on neural responses to messages in adolescents depends critically on the understanding of the cognitive mechanisms leading to effective persuasion (Suleiman & Dahl, Reference Suleiman and Dahl2017). For instance, knowledge about the cognitive mechanisms that lead to successful persuasion or message retransmission can illuminate key brain regions involved, which may differ among different types of campaigns (e.g., prevention-focused campaigns or campaigns aimed at changing a certain behavior) and in different adolescent populations (e.g., high sensation-seeking adolescents). In turn, studies that utilize neural signals to predict relevant health campaign outcomes can potentially inform our understanding and theorization of the mechanisms underlying persuasion in adolescents, which we discuss in more detail in the following section.
Understanding the underlying processes
In addition to complementing current tools for predicting campaign message effectiveness, neuroscience studies on adolescent development and persuasion can reveal common and distinct underlying processes that may be involved in adolescent persuasion and highlight the relationships among these processes. For example, recent adult neuroimaging evidence brings together several theories of persuasion under a more general framework of value-based decision-making (for a review, see Falk & Scholz, Reference Falk and Scholz2018). Additional insights into the underlying processes of adolescent persuasion could also inform media campaigns aimed at promoting adolescent health and well-being. Here, we discuss two sets of findings that may be relevant to health promotion: redirecting reward-seeking adolescents to engage in rewarding, pro-health behavior; and utilizing the power of social media.
Adolescents generally show heightened neural sensitivity to reward (Galvan et al., Reference Galvan, Hare, Parra, Penn, Voss, Glover and Casey2006; Somerville & Casey, Reference Somerville and Casey2010; van Duijvenvoorde et al., Reference van Duijvenvoorde, Op de Macks, Overgaauw, Gunther Moor, Dahl and Crone2014). Although individuals with heightened reward sensitivity demonstrate increased vulnerability to engaging in substance use, dysfunctional eating and risky driving (Loxton & Dawe, Reference Loxton and Dawe2001; O'Connor & Colder, Reference O'Connor and Colder2005; Brenhouse & Andersen, Reference Brenhouse and Andersen2011; Spear, Reference Spear2011; Galván & McGlennen, Reference Galván and McGlennen2013; Scott-Parker et al., Reference Scott-Parker, Watson, King and Hyde2013), higher reward sensitivity can also lead to developmentally adaptive outcomes such as better inhibitory control (Padmanabhan et al., Reference Padmanabhan, Geier, Ordaz, Teslovich and Luna2011), decreases in risky, delinquent behaviors (e.g., drinking alcohol, stealing, skipping school, using drugs) (Telzer et al., Reference Telzer, Fuligni, Lieberman and Galván2013) and declines in depressive symptoms (Telzer et al., Reference Telzer, Fuligni, Lieberman and Galván2014) in certain contexts. Evidence for both the adaptive and maladaptive consequences of heightened reward sensitivity suggests that, instead of a vulnerability to risky decisions that could harm adolescents’ health and well-being, adolescents’ heightened reward sensitivity should be considered a neurobiological marker for domain-general, approach-related behaviors that can also be channeled to promote positive outcomes (Telzer, Reference Telzer2016).
With this perspective in mind, an important open question is how to design health media campaigns that optimally promote the positive, pro-social tendencies for risk-taking while minimizing harmful outcomes. In other words, how can health professionals channel adolescents’ motivations to engage in high-stakes risk-taking and direct them toward behaviors that result in increased health and well-being? One possible approach is to emphasize values that are salient for adolescents, such as values relevant to social status, peer relationships, social acceptance and romantic interests in promoting positive rather than avoiding negative behaviors (Suleiman & Dahl, Reference Suleiman and Dahl2017). A recent study showed that, compared to traditional education messages, health messages that tap into adolescents’ need for autonomy and desire for social respect were more successful at influencing adolescent healthy eating behaviors (Bryan et al., Reference Bryan, Yeager, Hinojosa, Chabot, Bergen, Kawamura and Steubing2016). Similarly, in addition to the negative consequences of smoking, a campaign aimed at preventing adolescents from smoking could also leverage adolescence as a period of flexibility, exploration and learning to highlight pro-health values associated with smoking abstinence, such as an increased capacity for physical activity and improved social relationships. Given the social, psychological and behavioral complexities of health behavior and adolescent development, however, the corresponding health promotion strategies are likely to be equally nuanced and require direct input from adolescents.
Another direction in which insights from developmental and persuasion neuroscience studies could be helpful is the use of new media to disseminate and promote health messages. Social media is ubiquitous with regard to adolescent social networking and content sharing. Health campaigns increasingly use social media to disseminate health campaign messages in an attempt to influence attitudes and behaviors. Social media afford important functions such as content sharing and user commenting, supporting a greater extent of user engagement and participation compared to traditional mass media (e.g., TV, radio, and newspapers) (Neiger et al., Reference Neiger, Thackeray, Van Wagenen, Hanson, West, Barnes and Fagen2012; Thackeray et al., Reference Thackeray, Neiger, Hanson and McKenzie2008; Moorhead et al., Reference Moorhead, Hazlett, Harrison, Carroll, Irwin and Hoving2013). Sharing of campaign content on social media may create opportunities for exposure to individuals who would otherwise be unexposed, which may in turn support the diffusion of messages to a wider audience and improve campaign effectiveness (Hornik & Yanovitzky, Reference Hornik and Yanovitzky2003). Furthermore, liking, sharing and commenting behaviors by peers may provide social cues and social information in addition to the original health message. In a recent neuroimaging study, adolescents aged 13–18 years old were shown images that simulated photographs shared on Instagram, a social media platform, while in an fMRI scanner (Sherman et al., Reference Sherman, Payton, Hernandez, Greenfield and Dapretto2016). The results demonstrated that viewing pictures with many (compared with few) likes was associated with greater neural activity in brain regions implicated in reward processing, social cognition and attention, suggesting that the conferral of social approval from peers may increase the value of mediated messages and subsequently enhance message effects. Given adolescents’ heightened sensitivity to social evaluation (Crone & Dahl, Reference Crone and Dahl2012; Albert et al., Reference Albert, Chein and Steinberg2013), the social information (e.g., the sharing of a health message by one's friend) may facilitate persuasion among those who would not otherwise be persuaded by a health message. Finally, social media offer the opportunity for audience engagement, both with health professionals and with peers (for a review, see Heldman et al., Reference Heldman, Schindelar and Weaver2013). Elements of peer engagement and social support are particularly relevant for adolescent health promotion through social media; however, these same features can also backfire if comments and interpersonal communications about the campaign are negative (Hendriks et al., Reference Hendriks, van den Putte, de Bruijn and de Vreese2014). As such, it is important to understand the developmental trajectories and contextual influences that may determine the positive or negative direction of social influence. Systematic investigations are needed into whether and how health campaign professionals can manage a social media presence that promotes positive social feedback and community engagement within the affordances of social media sites. This action is crucial, as negative social feedback can not only undermine campaign message effectiveness, but also lead to boomerang effects (unintended consequences of attempts to persuade that result in opposite outcomes) (Southwell & Yzer, Reference Southwell and Yzer2009).
Conclusion: bridging from evidence to policy
Adolescence is a critical developmental period during which there is considerable opportunity for establishing life-long health-promoting behaviors. Conversely, there are great risks of initiating poor health behaviors that may be carried into adulthood. These point to the importance of gaining a better understanding of the brain's valuation system in adolescent health persuasion.
Given evidence that the brain undergoes significant development during adolescence, it is important to explore the ways in which development affects valuation. The understanding that the adolescent brain is undergoing functional reorganization and is more sensitive to social cues suggests that specific types of messages may be most effective during specific developmental windows. Integrating insights about neurodevelopmental trajectories with social and contextual factors that influence brain development (e.g., family support, social relationships, prior experiences) can further enhance the precision of these messages. Thus, investigations of the neurodevelopmental changes that occur during adolescence provide insights into the mechanisms that underlie successful health persuasion, as well as the potential to more accurately forecast which messages will work for which groups of adolescents.
As reviewed above, adolescents’ heightened sensitivity to rewards should be considered as a motivational force that facilitates learning and exploring, which can both increase vulnerabilities for unhealthy behaviors and increase opportunities for positive behaviors. Media campaign messages that effectively promote pro-health, pro-social channels of reward-seeking may prove more effective than those that focus solely on decreasing unhealthy and risky behaviors. Testing this hypothesis holds great promise for improving adolescent health trajectories. Finally, the content-sharing and commenting features of social media platforms provide opportunities for peer and community influence that could be particularly effective when communicating with adolescents. Many efforts are already being made to integrate social media into health promotion campaigns, and communication neuroscience offers strategies to streamline these efforts and ensure that the most effective messages reach the right audiences. Collectively, bringing together the fields of adolescent developmental science and communication neuroscience has the potential to significantly improve the health trajectories of young people.
Acknowledgements
We thank Robert Hornik, Nicole Cooper and Ron Dahl for their very valuable comments and discussions. Preparation of this manuscript was supported by the NIH New Innovator Award 1DP2DA03515601 (PI Falk), the Defense Advanced Research Projects Agency (DARPA) Grant D14AP00048 (PI Falk), the Army Research Laboratory under Cooperative Agreement Number W911NF-10-2-0022 (PI Falk) and HopeLab. The funding agencies played no role in the development of this manuscript. The views expressed in this manuscript are those of the authors and should not be interpreted as representing the views or policies of the funding agencies.
