Personality influence processing of social norms judgments.

Background: The knowledge of social norms (customary rules that govern behaviour in groups and societies) together with personality dispositions (traits) determines social decision behaviour in individual’s everyday life. Aim of the present fMRI study was to investigate the neural correlates of social norms processing and their bound with personality traits. Methods: Fourteen healthy right-handed subjects (13 female, mean age= 29 yrs) took part in the study. In each of tree runs subjects were presented with written sentences representing 3 different types of situation: 1. description of a behaviour that represents a violation of a social norm (intentional transgression); 21 sentences; 2. description of a normative social behaviour (adaptation of a social norm); 21 sentences; 3. description of a non social behaviour (control condition); 21 sentences. Subjects were asked to indicate whether they would act as described in the sentence or not by pressing one of two buttons. Functional images (TR= 2000) were acquired on a 3T Philips Intera system from 35 axial contiguous 3 mm slices (80 x 80 matrix) and were analyzed using SPM8 with a random effect model. Subject were administered with the BIS/BAS personality questionnaire (1) describing two motivational systems that underlie behaviour: an inhibition system (BIS) regulating aversive motives, in which the goal is to move away from something unpleasant and a behavioural activation system (BAS) regulating appetitive motives, in which the goal is to move toward something. There are three BAS- subscales: The Drive (D) scale pertains to the persistent pursuit of desired goals; the Fun-seeking scale reflects both a desire for new rewards and a willingness to approach a potentially rewarding event on spur of moment; finally Reward Responsiveness (RR) focus on positive responses to the occurrence or anticipation of reward. To test whether personality traits influenced the social norms processing, the BIS/BAS scale and its sub-scale scores were correlated with sBOLD signal changes during the social decision task (violation and adaptation to social norms vs control condition). Results: The processing of social decision (violation and adaptation to social norms) sentences with respect to control sentences evoked extensive bilateral activations mainly in the prefrontal and temporal regions; significant cluster were also found in thalamus and midbrain. No differences were found between the processing of item describing a violation and an adaptation to social norms. The correlation with BIS/BAS questionnaire showed significant BOLD signal changes: BAS-D scores positively correlated with activations of middle and inferior frontal cortex of both hemisphere, left amygdala, right putamen and cerebellum of both side. BAS-RR scores correlated with bilateral activations in superior and middle frontal gyrus, anterior cingulate, middle temporal gyrus and substantia nigra. No significant cluster was found in the correlation with BIS score. Conclusions: fMRI results showed that the neural network subserving social decision making includes an extended activation of the bilateral prefrontal cortex. BAS personality traits influenced the activity of this network. The BAS system governs responses to positive, rewarding stimuli resulting in approach behaviour. This includes the response to happy faces, monetary incentives and the expectancy of reward (2). Our data revealed that BAS high individuals showed an enhanced activity in this reward system suggesting an higher dependency on social approval. On the contrary, BIS system (the inhibition one) seem not to influence the processing of social norms. Summing up, the presents study suggests that personality dispositions are a fundamental source of information for social decision making. Bibliography 1. Carver, C. S., & White, T. L. (1994). Behavioral inhibition, behavioral activation, and affective responses to impending reward and punishment: The BIS/BAS scales. Journal of Personality and Social Psychology, 67, pp. 319-333. 2. Kennis M, Rademaker AR, Geuze E (2012) Neural correlates of personality: An integrative review. Neurosci Biobehav Rev. 37(1): pp. 73-95.