Hostility bias or sadness bias in excluded individuals: does anodal transcranial direct current stimulation of right VLPFC vs. left DLPFC have a mitigating effect?

Exclusion has multiple adverse effects on individual’s well-being. It induces anger and hostile cognitions leading to aggressive behavior. The purpose of this study was to test whether exclusion would affect recognition of anger on ambivalent faces of the excluders. We hypothesized that exclusion would elicit more anger encoding (hostility bias) than inclusion, but this effect would be mitigated by anodal tDCS of right VLPFC or left DLPFC—regions engaged in negative affect regulation. Participants ( N = 96) were recognizing emotions (anger, sadness, happiness) on ambiguous faces of individuals who—as they were told—liked them or not. Results showed that exclusion induced more sadness bias. tDCS to VLPFC decreased anger and increased sadness recognition on excluders’ faces compared with includers’ faces, expressing a mixture of these two emotions. Additionally, stimulation to VLPFC and DLPFC decreased latencies for faces expressing sadness (sad-angry and happy-sad) but increased for happy-angry faces. Stimulation to VLPFC also increased reaction time to excluders faces while stimulation of DLPFC decreased reaction latency to includers faces. Results were discussed with the reference to the form of exclusion, motivational mechanism affected by disliking but also to lateralization (valence vs. arousal theory) and cortical regions engaged in encoding sadness after a threat to belonging.