A Comparison of the Electrocortical Response to Monetary and Social Reward

Amanda Distefano; Felicia Jackson; Amanda R. Levinson; Zachary P. Infantolino; Johanna M. Jarcho; Brady D. Nelson

Disclosures

Soc Cogn Affect Neurosci. 2018;13(3):247-255. 

In This Article

Abstract and Introduction

Abstract

Affective science research on reward processing has primarily focused on monetary rewards. There has been a growing interest in evaluating the neural basis of social decision-making and reward processing. The present study employed a within-subject design and compared the reward positivity (RewP), an event-related potential component that is present following favorable feedback and absent or reduced following unfavorable feedback, during monetary and social reward tasks. Specifically, 114 participants (75 females) completed a monetary reward task and a novel social reward task that were matched on trial structure, timing, and feedback stimuli in a counterbalanced order. Results indicated that the monetary and social RewP were of similar magnitude, positively correlated and demonstrated comparable psychometric properties, including reliability and dependability. Across both the monetary and social tasks, women demonstrated a greater RewP compared with men. This study provides a novel methodological approach toward examining the electrocortical response to social reward that is comparable to monetary reward.

Introduction

The evaluation of feedback is an important component of decision-making and reinforcement learning (Holroyd and Coles, 2002; Schultz, 2006). Event-related potentials (ERPs) are often used to examine this cognitive-affective process given their high temporal resolution. ERP studies have often utilized laboratory gambling or guessing tasks to measure the reward positivity (RewP) in response to feedback (Hajcak et al., 2006; Bernat et al., 2015; Novak and Foti, 2015). The RewP is a positive-going deflection in the ERP signal that peaks ~250-350 ms after favorable feedback (e.g. winning money) and is absent or reduced following unfavorable feedback (e.g. losing money). The RewP is associated with behavioral and self-report measures of reward sensitivity (Bress and Hajcak, 2013) and the engagement of brain regions implicated in reward-processing, including the medial prefrontal cortex and striatum (Carlson et al., 2011; Foti et al., 2014).

Affective science research on reward processing has primarily focused on monetary outcomes; however, there has been growing interest in evaluating the neural basis of social decision-making and reward processing (e.g. Guyer et al., 2012; Bhanji and Delgado, 2014; Vrtička et al., 2014; Jarcho et al., 2015). Functional magnetic resonance imaging (fMRI) research suggests that there is a common neural system implicated in reward-learning for both non-social (e.g. monetary) and social rewards. For example, Izuma et al. (2008) found that both positive feedback regarding one's reputation and receiving a monetary reward activated an overlapping aspect of the striatum. Indeed, the striatum is engaged during trial and error-based learning tasks (Daniel and Pollmann, 2014) and reward-based learning tasks (Lin et al., 2012) regardless of the type of reward received. Moreover, Hausler et al. (2015) found that the reward of scoring a goal in soccer vs winning money activated similar regions of prefrontal cortex and striatum. Some investigations have found dissociable neural networks for the processing of monetary and social reward (Rademacher et al., 2010; Chan and Cheung, 2016); however, many of these studies have employed affective images or smiling faces—stimuli which do not map well on to the actual experience of being rewarded. Together, these fMRI findings suggest that a common neural system is likely involved in reward processing for both nonsocial and social rewards.

ERP researchers have utilized many different tasks to examine the neural response to social feedback. For example, Kujawa et al. (2014) employed an 'Island Getaway' task, based on the television show 'Survivor', in which participants voted to remove players from an island, and received either acceptance or rejection feedback from peers. Results indicated that a larger RewP was elicited in response to acceptance relative to rejection feedback. Using a different social task, Sun and Yu (2014) also found a larger RewP in response to acceptance relative to rejection feedback. Finally, van der Veen et al. (2016) found that during a social task a larger RewP was elicited by acceptance feedback that was unexpected relative to expected. These data suggest that a RewP is elicited by both non-social (e.g. monetary) and social (e.g. acceptance) reward. The one study to compare the monetary and social RewP in the same participants found that monetary feedback elicited a larger RewP compared with social feedback (Flores et al., 2015). However, this investigation examined peak-to-peak amplitude, which is highly sensitive to noise (Clayson et al., 2013). Given this important limitation, it is still unclear whether the RewP elicited by monetary reward is comparable to that elicited by social reward.

This study employed a within-subject design and compared the electrocortical response to monetary and social reward. Specifically, 114 participants completed a monetary reward task (i.e. the doors task; Proudfit, 2015) and a novel social reward task in a counterbalanced order. One critical limitation to the extant literature comparing monetary and social reward processing has been the presence of several confounds between tasks (e.g. picture of money versus facial expression). To minimize potential confounds, this study employed monetary and social reward tasks that were matched on trial structure, timing and feedback stimuli. Given the existing research demonstrating that monetary and social reward engage similar neural substrates and electrocortical activation, we hypothesized that feedback indicating a favorable outcome (i.e. monetary gain, social acceptance) would elicit a larger RewP relative to feedback indicating an unfavorable outcome (i.e. monetary loss, social rejection). We also hypothesized that the magnitude of the RewP would not differ between the monetary and social reward tasks.

The RewP is a promising individual difference measure of reward sensitivity that has demonstrated good psychometric properties (Levinson et al., 2017; Luking et al., 2017), but supporting evidence has focused exclusively on the monetary RewP. To further elucidate the psychometric properties of the RewP, we examined the intra-individual correlation, reliability, and dependability of the monetary and social RewP. We hypothesized that the monetary and social RewP would be positively correlated with each other, and demonstrate comparable psychometric properties.

Research has indicated important sex differences in neural reactivity to emotional and motivational information (Stevens and Hamann, 2012). For example, one fMRI investigation examined whether men and women differed in neural activation in anticipation of two forms of reward: money and social approval (Spreckelmeyer et al., 2009). A wider network of brain areas were activated for monetary, compared with social, rewards in men. In contrast, anticipating both monetary and social rewards in women activated comparable brain regions. These results are consistent with previous evidence suggesting that emotional differences between men and women may vary depending on the type of stimulus or event (e.g. social or nonsocial) (Schirmer et al., 2013). However, the literature has been mixed regarding sex differences in the monetary RewP. Specifically, two investigations found a greater RewP in 9-year-old boys compared with girls (Kujawa et al., 2015) and adult men compared with women (Novak et al., 2016). However, another investigation reported a greater RewP in 16 to 17 year-old girls compared with boys (Santesso et al., 2011), while others have found no sex differences (Foti and Hajcak, 2009; Bress et al., 2012). The limited studies that have examined sex differences in the social RewP have also been mixed: one reported a greater social RewP in young adult women compared with men (van der Veen et al., 2016) and another reported no sex difference in the RewP in 10 to 15 year-old children (Kujawa et al., 2014). To further examine this issue, this study tested for sex differences in the monetary and social RewP. Given the mixed literature on sex differences in the RewP, we had no specific hypotheses for these analyses.

Finally, aberrations in the brain's reward system are central to several etiological models of depression (Russo and Nestler, 2013). Consistent with this perspective, a blunted RewP has been associated with more severe expression of depression symptoms and syndromes (Foti and Hajcak, 2009; Bress et al., 2012,, 2015; Nelson et al., 2016). A growing number of studies have found that social rewards elicit depression-related differences in the brain's reward system (Forbes, 2009; Silk et al., 2014; Olino et al., 2015). However, no study has examined, in the same sample of individuals, the association between depression symptoms and neural response to monetary and social rewards. Therefore, this study examined the association between the monetary and social RewP and individual differences in depression symptoms. We hypothesized that greater depression symptoms would be associated with a smaller RewP, but we had no specific hypothesizes regarding differences between monetary and social tasks.

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