Modulation of Reasoning Bias and Brain Activation by Serotonin Transporter Genotype and Emotional Content

Reasoning often occurs under emotionally charged, opinion-laden circumstances. The belief-bias effect indexes the extent to which reasoning is based upon beliefs rather than logical structure. We hypothesized that emotional content will increase this effect, particularly for individuals with higher emotional reactivity. The serotonin transporter genotype is associated with emotional reactivity such that it is higher in carriers of the S than L allele. Thus, we expected belief bias to be higher in SS/SLG than in LALA carriers for relational reasoning problems with emotional, but not non-emotional, content. Indeed, SS/SLG carriers were less accurate selectively for evaluating relational reasoning emotional problems with belief-logic conflict relative to LALA carriers. Further, genotype accounted for the association between trait anxiety and emotional belief bias. Thus, deductive reasoning, an important ability associated with academic achievement and socio-emotional intelligence, is sensitive to differences in emotionality rooted in serotonin neurotransmitter function.