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Misestimating risk could lead to disadvantaged choices such as initiation of drug use (or gambling) and transition to regular drug use (or gambling). Although the normative theory in decision-making under risks assumes that people typically take the probability-weighted expectation over possible utilities, experimental studies of choices among risks suggest that outcome probabilities are transformed nonlinearly into subjective decision weights by a nonlinear weighting function that overweights low probabilities and underweights high probabilities. Recent studies have revealed the neurocognitive mechanism of decision-making under risk. However, the role of modulatory neurotransmission in this process remains unclear. Using positron emission tomography, we directly investigated whether dopamine D 1 and D 2 receptors in the brain are associated with transformation of probabilities into decision weights in healthy volunteers. The binding of striatal D 1 receptors is negatively correlated with the degree of nonlinearity of weighting function. Individuals with lower striatal D 1 receptor density showed more pronounced overestimation of low probabilities and underestimation of high probabilities. This finding should contribute to a better understanding of the molecular mechanism of risky choice, and extreme or impaired decisionmaking observed in drug and gambling addiction.

The purpose of this study was to examine the effect of decision frame, decision justification on risky choice. Subjects were 158 men and women. The results were as follows.(I) In the condition where no justification was requested, a framing effect (Tversky & Kahneman, 1981) was observed: Most of the subjects chose the riskless option when decision options were phrased positively in terms of gains, whereas most of the subjects chose the risky option when options were phrased negatively in terms of losses. (2) However, in the condition where justification was requested, the framing effect was not observed: Most of the subjects showed a consistent choice pattern. (3) The subjects in the justification-requested condition tended to choose risky option more often than the subjects in the no justificationrequested condition did.

How does one deal with unfair behaviors? This subject has long been investigated by various disciplines including philosophy, psychology, economics, and biology. However, our reactions to unfairness differ from one individual to another. Experimental economics studies using the ultimatum game (UG), in which players must decide whether to accept or reject fair or unfair offers, have also shown that there are substantial individual differences in reaction to unfairness. However, little is known about psychological as well as neurobiological mechanisms of this observation. We combined a molecular imaging technique, an economics game, and a personality inventory to elucidate the neurobiological mechanism of heterogeneous reactions to unfairness. Contrary to the common belief that aggressive personalities (impulsivity or hostility) are related to the high rejection rate of unfair offers in UG, we found that individuals with apparently peaceful personalities (straightforwardness and trust) rejected more often and were engaged in personally costly forms of retaliation. Furthermore, individuals with a low level of serotonin transporters in the dorsal raphe nucleus (DRN) are honest and trustful, and thus cannot tolerate unfairness, being candid in expressing their frustrations. In other words, higher central serotonin transmission might allow us to behave adroitly and opportunistically, being good at playing games while pursuing self-interest. We provide unique neurobiological evidence to account for individual differences of reaction to unfairness.positron emission tomography | decision-making | fairness

BackgroundPatients with schizophrenia and their families have suffered greatly from stigmatizing effects. Although many efforts have been made to eradicate both prejudice and stigma, they still prevail even among medical professionals, and little is known about how contact with schizophrenia patients affects their attitudes towards schizophrenia.MethodsWe assessed the impact of the renaming of the Japanese term for schizophrenia on clinical residents and also evaluated the influence of contact with schizophrenia patients on attitudes toward schizophrenia by comparing the attitudes toward schizophrenia before and after a one-month clinical training period in psychiatry. Fifty-one clinical residents participated. Their attitudes toward schizophrenia were assessed twice, before and one month after clinical training in psychiatry using the Implicit Association Test (IAT) as well as Link’s devaluation-discrimination scale.ResultsThe old term for schizophrenia, “Seishin-Bunretsu-Byo”, was more congruent with criminal than the new term for schizophrenia, “Togo-Shitcho-Sho”, before clinical training. However, quite opposite to our expectation, after clinical training the new term had become even more congruent with criminal than the old term. There was no significant correlation between Link's scale and IAT effect.ConclusionsRenaming the Japanese term for schizophrenia still reduced the negative images of schizophrenia among clinical residents. However, contact with schizophrenia patients unexpectedly changed clinical residents’ attitudes towards schizophrenia negatively. Our results might contribute to an understanding of the formation of negative attitudes about schizophrenia and assist in developing appropriate clinical training in psychiatry that could reduce prejudice and stigma concerning schizophrenia.

This article evaluates the effects of two types of rewards (performance-contingent versus engagement-contingent) on self-regulation, intrinsic motivation and creativity. Forty-two undergraduate students were randomly assigned to three conditions; i.e. a performance-contingent reward group, an engagement-contingent reward group and a control group. Results provide little support for the negative effects of performance rewards on motivational components. However, they do indicate that participants in the engagement-contingent reward group and the control group achieved higher rated creativity than participants in the performance-contingent reward group. Alternative explanations for this finding are discussed.

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