Valence and arousal are primary dimensions of affective stimuli. An interaction of these two factors on affective processing is largely unknown. In this study, the processing of affective pictures was investigated in an orthogonal valence (positive vs. negative) by arousal (high vs. low) task design. Participants were instructed to passively view each presented picture and did not need to make any responses. The valence by arousal interaction was observed on three event-related potential (ERP) components, including the P2 (160-190 ms), N2 (220-320 ms) and late positive potential (LPP) (400-700 ms). This interaction revealed that negative pictures evoked larger neural responses compared with positive pictures (i.e., negative bias) at the high-arousal level, whereas negative pictures evoked smaller neural responses than positive pictures (i.e., positive offset) at the low-arousal level. The current results suggest that the effect of emotional valence on affective picture perception is modulated by levels of arousal at both early and late stages of processing. Finally, the main effect of valence was evident in the P1 component (90-110 ms) and arousal effect in the N1 component (120-150 ms).

Recent evidence indicates that empathic responses to others' pain are modulated by various situational and individual factors. However, few studies have examined how empathy and underlying brain functions are modulated by social hierarchies, which permeate human society with an enormous impact on social behavior and cognition. In this study, social hierarchies were established based on incidental skill in a perceptual task in which all participants were mediumly ranked. Afterwards, participants were scanned with functional magnetic resonance imaging while watching inferior-status or superior-status targets receiving painful or non-painful stimulation. The results revealed that painful stimulation applied to inferior-status targets induced higher activations in the anterior insula (AI) and anterior medial cingulate cortex (aMCC), whereas these empathic brain activations were significantly attenuated in response to superior-status targets' pain. Further, this neural empathic bias to inferior-status targets was accompanied by stronger functional couplings of AI with brain regions important in emotional processing (i.e. thalamus) and cognitive control (i.e. middle frontal gyrus). Our findings indicate that emotional sharing with others' pain is shaped by relative positions in a social hierarchy such that underlying empathic neural responses are biased toward inferior-status compared with superior-status individuals.

The current study explored whether earned entitlement modulated the perception of fairness in three experiments. A preliminary resource earning task was added before players decided how to allocate the resource they jointly earned. Participants’ decision in allocation, their responses to equal or unequal offers, whether advantageous or disadvantageous, and subjective ratings of fairness were all assessed in the current study. Behavioral results revealed that participants proposed more generous offers and showed enhanced tolerance to disadvantageous unequal offers from others when they performed worse than their presumed “partners,” while the reverse was true in the better-performance condition. The subjective ratings also indicated the effect of earned entitlement, such that worse performance was associated with higher perceived feelings of fairness for disadvantageous unequal offers, while better performance was associated with higher feelings of fairness for advantageous unequal offers. Equal offers were considered “fair” only when earned entitlement was even between two parties. In sum, the perception of fairness is modulated by an integration of egalitarian motivation and entitlement. In addition to justice principles, participants were also motivated by self-interest, such that participants placed more weight on entitlement in the better-performance condition than in the worse-performance condition. These results imply that earned entitlement is evaluated in a self-serving way.

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