Reinforcement learning as an intermediate phenotype in psychosis? Deficits sensitive to illness stage but not associated with polygenic risk of schizophrenia in the general population.

BACKGROUND: Schizophrenia is a complex disorder in which the causal relations between risk genes and observed clinical symptoms are not well understood and the explanatory gap is too wide to be clarified without considering an intermediary level. Thus, we aimed to test the hypothesis of a pathway from molecular polygenic influence to clinical presentation occurring via deficits in reinforcement learning. METHODS: We administered a reinforcement learning task (Go/NoGo) that measures reinforcement learning and the effect of Pavlovian bias on decision making. We modelled the behavioural data with a hierarchical Bayesian approach (hBayesDM) to decompose task performance into its underlying learning mechanisms. Study 1 included controls (n = 29, F|M = 0.81), At Risk Mental State for psychosis (ARMS, n = 23, F|M = 0.35) and FEP (First-episode psychosis, n = 26, F|M = 0.18). Study 2 included healthy adolescents (n = 735, F|M = 1.06), 390 of whom had their polygenic risk scores for schizophrenia (PRSs) calculated. RESULTS: Patients with FEP showed significant impairments in overriding Pavlovian conflict, a lower learning rate and a lower sensitivity to both reward and punishment. Less widespread deficits were observed in ARMS. PRSs did not significantly predict performance on the task in the general population, which only partially correlated with measures of psychopathology. CONCLUSIONS: Reinforcement learning deficits are observed in first episode psychosis and, to some extent, in those at clinical risk for psychosis, and were not predicted by molecular genetic risk for schizophrenia in healthy individuals. The study does not support the role of reinforcement learning as an intermediate phenotype in psychosis.

Twin classroom dilemma: To study together or separately?

There is little research to date on the academic implications of teaching twins in the same or different classroom. Consequently, it is not clear whether twin classroom separation is associated with positive or negative educational outcomes. As a result, parents and teachers have insufficient evidence to make a well-informed decision when twins start school. This study addresses two research questions: Are there average positive or negative effects of classroom separation? Are twins taught in different classes more different from each other than twins taught in the same class? Twin pairs from two large representative samples from Quebec (Canada) and the United Kingdom were evaluated across a large age range (7 to 16 years) on academic achievement, several cognitive abilities and motivational measures. Our results show almost no sizable positive or negative average effect of classroom separation on twins' achievement, cognitive ability and motivation. Twin pairs at age 12 (Quebec, Canada) and at age 16 (United Kingdom) were slightly more similar on achievement if placed in the same classroom, with slightly greater similarity among monozygotic twins than dizygotic twins. However, the few effects found were weak, and it remains unclear whether they result from classroom separation or other factors. These results suggest that in terms of educational outcomes, policymakers should not impose rigid guidelines to separate twin pairs during their education. The choice of whether to educate twin pairs together or separately should be up to parents, twins and teachers, in response to twins' individual needs. (PsycINFO Database Record