We recognize few generalizations can be made with a sample of 19 adolescents; however, an a priori power analysis indicated a sample of 18 participants would be sufficient to conclude significant differences. Our experimental peer influence manipulation, while novel, has limitations, such as we did not measure whether or how attractive participants believed the photographs of the “peer” in manipulation to be. Additionally, we were not able to time how long participants viewed the data and photograph on the screen, though we did monitor participants from our periphery to ensure they saw the monitor before the experimenter approached them to proceed. We are unable to draw conclusions about whether an opposite-sex peer is more influential than a same-sex peer because we did not have a comparison condition in our study. However, our study is the first to successfully introduce an opposite-sex peer influence manipulation in an adolescent sample.While we find our result pertaining to ventral striatum activation enticing, we hesitate to draw broad conclusions, as the variation in self-reported resistance to peer influence is slight. We suggest future research enroll a larger sample to test the differences, and perhaps focus on collecting self-esteem and risk preference information to determine whether these indices moderate or predict experimentally manipulated and self-reported susceptibility to peer influence. The present study validated the Resistance to Peer Influence questionnaire by using an experimentally manipulated peer influence task that asked adolescents about their real-world social behaviors. While other studies have manipulated peer influence in adolescence, we successfully did so in an ecologically valid manner—by collecting information from adolescents regarding their likelihood to engage in risky social behaviors typical of teenagers. While overall self-reported peer influence was not directly associated with experimentally manipulated peer influence, we found variation within question types,equipment for growing weed such that specific types of peer influence were more predictive of changes in specific behaviors .
We propose that adolescents demonstrated greater variability within these types of questions because they are not susceptible to all forms of risk taking, and do not partake in all types of risks. We conclude that adolescents who are more susceptible to peer influence are more considerate of their peers’ perspectives and have a greater desire to be accepted socially—leading to an increased likelihood to engage in behaviors adolescents believe their peers endorse. Interacting with peers is critical for social development, and how one chooses to respond to peer feedback may have significant implications for adolescents, particularly because of the heightened experimentation with drugs of abuse and peer influence during this developmental window. Sensitivity to peer feedback, peer influence, and substance use do not occur independently during adolescence; but surprisingly, these phenomena are often assessed independently of one another. In the last decade or so, research using brain imaging has revealed the neural substrates that might underlie these characteristic adolescent behaviors. One region in particular, the ventral striatum, has been linked to risk taking and susceptibility to peer influence . This dissertation makes a novel contribution to the literature in that it associates ventral striatum response to social violations of expectations with self-reported real-world social behaviors in adolescents. This dissertation implemented multiple methodologies, including self-report, novel experimental designs, and fMRI to examine how adolescents respond to peer feedback, and whether their response is associated with their real-world social behaviors.
Results indicate that adolescents prefer to learn they are accurate about their expectations that pertain to their friendship, over and above learning something better than expected from a friend . This suggests a social violation of expectations from a friend is not necessarily a welcomed experience for an adolescent, perhaps because adolescents encounter an abundance of social uncertainty in their daily lives and are on alert for violations in their social encounters in an effort to adjust their behavior to fit in with their peers. However, a positive violation of expectations from an unknown other may be a welcomed experience by comparison because adolescents would have fewer relationship priors by which to set their expectations. Thus, for unknown peers, we suggest positive violations of expectations may be rewarding to an adolescent, while for well-known peers, non-violations of expectations are more rewarding by comparison. It is then likely that learning they are accurate about their social expectations within their friendship is somewhat of a “relief” signal , whereby adolescents do not need to make the cognitive effort to update their expectations about a relationship that is important to them. It is unknown whether there are developmental differences in meeting or exceeding expectations within a close friendship. We suggest future studies examine differences in meeting/positively violating expectations in an adolescent and adult sample between close friends and unknown-peers to elucidate these supposed differences, as this information may have implications for further identifying a sensitive period for social learning. This study also revealed increased activation in the ventral striatum for positive social violations of expectations, and increased activation in the insula and subgenual anterior cingulate cortex for negative social violations of expectations, though not for non-social violations of expectations. Taken together with self-reported happiness, these results suggest that during adolescence, learning a friend said something better than expected about the friendship is rewarding, while learning a friend said something worse than expected about the friendship is disconcerting by comparison.
This study presents novel fMRI and self-report results comparing valence of social statements, and suggests that adolescents are sensitive to social feedback from a friend. In addition to the neurobiological and self-reported happiness results, this study revealed that adolescents were fastest when their expectations were increasingly positively exceeded. This result could have implications for understanding adolescent behavior in an affective context, where experiencing a negative social violation of expectations from a friend may give a teenager reason to pause and update his expectations; a social positive violation of expectations from a friend may accelerate decision-making in a social context. Future research should consider assessing the differences between positive social violations of expectations, and meeting social expectations within a close friendship in adolescents—while both may be rewarding, the violation magnitude of the former may be more inherently confusing or conflicting, and result in more impulsive behavior. Ventral striatum response to violations of expectations from a friend was found to be associated with real-world socially acceptable substance use, as reported by adolescents . Categorically defining substances by which are “socially acceptable” compared to those that are less socially acceptable or are perceived to have greater consequences by comparison may elucidate distinct differences in the association of recruited brain regions or behavioral differences. Most research has associated ventral striatum response to general substance use ,grow tables 4×8 including drugs not frequently used by adolescents. Because adolescents report using alcohol, tobacco, and cannabis more so than other substances , this association suggests that the rewarding experience of using these substances transcends the neurochemical rewarding effects of them and perhaps permeates the rewarding experience of social interactions. In addition to the results presented in Chapter 3, this also suggests that substance use would not be as rewarding to adolescents if it was independent of social factors, and that the interaction of using these substances that are socially acceptable exacerbates the reward response. The aforementioned theory is supported by the results reported in Chapter 4, such that the adolescents who reported using socially acceptable substances reported being susceptible to peer influence and demonstrated susceptibility to experimentally manipulated peer influence, indicating they cared about being accepted by their peers, using substances perhaps as a means to be accepted by their peers and experience a greater sensation of reward.
The experimental peer influence task was validated by the self-report resistance to peer influence measure, contributing to the literature in suggesting likelihood to use socially acceptable substances increases the more adolescents demonstrate a desire to fit in. Thus, adolescents who avoid using these types of substances may not care as much about peer acceptance and social status amongst their peers—perhaps finding reward either in prosocial or academic activities; while adolescents who use substances that are less socially acceptable by comparison may find more reward in using substances than the contextual factors associated with them —suggesting environmental and historical factors may contribute to these individual differences . This suggests that using tobacco, alcohol, and cannabis occurs in adolescence due to the socially rewarding experience that is associated with them. While novel, the social violations of expectations task used in Study 1 precludes us from identifying whether ventral striatal response to social or non-social reward may be more closely associated with self reported substance use and susceptibility to peer influence—as it is a social task. While our data suggest ventral striatum activation to social violations is associated with the aforementioned variables, future studies should consider implementing a social and non-social design to compare whether ventral striatum activation to rewarding social feedback is more closely associated with likelihood to use substances and succumb to peer influence. Taken together, this research suggests ventral striatal response to social feedback from a friend is associated with self-reported real world socially rewarding behaviors. Future research should consider developing a model to examine adolescent responses to socially rewarding experiences as a predictor of behaviors that occur in social contexts, such as using socially acceptable substances and succumbing to peer influence. This association trifecta provides essential insight into adolescent risk taking, suggesting that beyond the chemical properties of reward, social feedback may exacerbate the experience of reward in adolescence, such that adolescents who care to be accepted by their peers and are attuned to peer feedback are more likely to engage in socially accepting behaviors. This research has important implications for examining real world behaviors through a violations of expectations framework. Results from all three studies indicate there may be distinct types of adolescents—those who are already using socially acceptable substances and require a greater violation of expectations to experience reward; and those who are likely to use socially acceptable substances, are susceptible to peer influence, and require a decreased violation of expectations to experience reward by comparison. Using this basic social learning construct may function as an aid in predicting which adolescents may fit into either group, and whether the adolescents who are susceptible to peer influence eventually become more resistant to it, and require a greater social violation of expectations in order to experience the sensation of reward in a social context.People with HIV are twice as likely to engage in heavy alcohol use and two to three times more likely to meet criteria for an alcohol use disorder in their lifetime than the general population . Heavy alcohol use not only promotes the transmission of HIV through sexual risk-taking behavior and non-adherence to antiretroviral therapy , but also directly exacerbates HIV disease burden by compromising the efficacy of ART and increasing systemic inflammation . In addition to increased risk for physical illness , there is substantial evidence indicating that comorbid HIV and heavy alcohol use is more detrimental to brain structure and results in higher rates of neurocognitive impairment than either condition alone . The impact of comorbid HIV and heavy alcohol use on the central nervous system is especially important to consider in the context of aging. The population of older adults with HIV is rapidly growing; approximately 48% of PWH in the U.S. are aged 50 and older and the prevalence of PWH over the age of 65 increased by 56% from 2012 to 2016 . Trajectories of neurocognitive and brain aging appear to be steeper in PWH , possibly due to chronic inflammation and immune dysfunction, long-term use of ART, frailty, and cardiometabolic comorbidities . In addition to HIV, rates of alcohol use and misuse are also rising in older adults . The neurocognitive and physical consequences of heavy alcohol use are more severe among older than younger adults, and several studies also report accelerated neurocognitive and brain aging in adults with AUD . While mechanisms underlying these effects are poorly understood, older adults may be more vulnerable to alcohol-related neurotoxicity due to a reduced capacity to metabolize alcohol, lower total-fluid volume, and diminished physiologic reserve to withstand biological stressors . Altogether, these studies support a hypothesis that PWH may be particularly susceptible to the combined deleterious effects of aging and heavy alcohol use. For example, in a recent longitudinal report, Pfefferbaum et al. reported that PWH with comorbid alcohol dependence exhibited faster declines in brain volumes in the midposterior cingulate and pallidum above and beyond either condition alone.