Exaggerated envy and guilt measured by economic games in Japanese women with anorexia nervosa

Anorexia nervosa (AN) is characterized by distorted body image and excessive dieting [1]. Individuals with AN feel guilt for “indulgent” eating or loss of control in an eating setting [2], and they feel envy when they see someone very slim [3]. In this manner, those with AN are assumed to express high levels of guilt and envy [4, 5]. However, these emotional reactions can be observed not only in food/body contexts but also in more general situations. Adolescents with AN showed more increased guilt than healthy ones [6], and increased envy may have roots deep in the psychopathology of AN [7].

To understand these emotions, economics games, which can assess decision-making in social situations [8] and provide a quantitative value to examining the psychopathology by predicting optimal adaptation to a changing environment [9], have been used in psychiatric populations [10, 11]. In particular, ultimatum game (UG), focusing on interpersonal behavior when splitting a sum of money between two players, is one of the most widely used tasks, as guilt and envy are addressed with this task [12]. The proposer suggests the distribution amount, and then the responder decides to accept or reject the proposal. If the responder accepts, the proposed distribution is the final allocation for the two players. If the responder rejects the proposal, both players receive nothing. Although theory predicts that the responder accepts all offers and that the proposer offers the smallest amount [13], behavioral economics consistently demonstrates that people do not necessarily maximize their allocation [14]. It has been assumed that people tend to minimize inequity in outcomes [11]. One explanation for such behavior is that guilt and envy play roles in the game. Rejecting low offers in UG implies envy, which is the preference to prevent the opposing person earning more than oneself, and offering equal allocation is derived from the desire to minimize guilt of having too much [15]. Given that both guilt and envy could be measured in the two different roles of UG (proposer, responder), we decided to use UG with the aim of quantifying these emotions in social situations among AN patients. We assumed that behaviors with exaggerated envy and guilt could be detected in AN patients, resulting in a high rejection rate of low offers and egalitarian allocation.

We detected significant differences in behavior and strategy between Japanese female AN and matched HC in UG. The results of UG indicate that excessive offer amount and excessive rejection rate reflect guilt and envy, respectively [23]. The proposer of UG has to decide the distribution, the conflict being between self-profit and preference for fairness [18, 23]. As decisive factors for the responder’s behavior, altruistic punishment and inequity aversion underlie the rejection of an unfair offer [24]. The results of the AN group indicate that the higher distribution amount as proposer and the lower accepting behavior as responder may reflect a strong preference for fairness. The decision-making strategy of responders also showed that AN patients placed great emphasis on fairness.

One explanation for the strong preference of the AN patients for fairness might be linked to the social emotions guilt and envy. In UG, individuals with more guilt were found to propose fair allocation, and those with more envy tended to reject unfair offer [25]. Eating disorder patients are believed to demonstrate high sensitivity to guilt and envy, which are not limited to eating settings [4, 5]. Therefore, exaggerated guilt and envy of AN patients can affect not only their own behavior concerning eating attitude and body shape, but also decision-making in interpersonal situations.

Another explanation for the strong preference for fairness is the fact that AN patients show psychological inflexibility motivated by demand of certainty and fear of social rejection and negative evaluation by others [26]. This inflexibility leads to over-reliance on social norms and rules for behavior to reduce ambiguity/risk and mistakes. In fact, the risk-aversive trait was detected in a decision-making study of AN [27]. AN patients may have chosen ‘excessive’ fair allocation as a more certain condition in UG in order to avoid blame. AN patients may stick to the normative principle that people ‘should’ follow and consequently make inflexible decisions in interpersonal situations. This notion might partly explain the result that, despite the exaggerated emphasis on fairness, it was not positively correlated with the mean offered amount by the proposer in AN, whereas HC showed a rational positive correlation between them.

Several limitations of the current study need to be considered. First, as the number of participants was limited, we must exercise caution regarding interpretation of the results until similar behavioral experiments can be performed with larger samples of AN patients. Second, for a better understanding of the decision-making process linked to the psychopathology of AN, the development of decision-making experiments based on other than monetary rewards is strongly awaited. Third, we selected the items of post-experimental questionnaires with strong hypothesis on the basis of previous studies and the results were reasonable and in agreement with our hypothesis. However, unfortunately, we did not perform correction for multiple comparisons. Future replication studies are recommended.

Given that poor decisions are related to poor real-life outcomes, intervention targeting impaired decision-making may improve clinical outcomes and quality of life [28]. For instance, neuroimaging studies have demonstrated the neural correlates of guilt and envy [e.g., medial prefrontal cortex [29, 30] and anterior cingulate [31], respectively], and malfunctions of these midline structures were repeatedly reported in AN [32]. Further investigations of economic behavioral experiments concurrent with neuroimaging are urgently required. Moreover, neuromodulation targeting these emotions also merits further investigation. In conclusion, behavioral economics tools are useful for the evaluation of the altered emotions and decision-making that are rooted deep in the psychopathology of AN.