Belief Updating Bias And Anhedonia In Patients With Schizophrenia And Individuals With Schizotypy

Schizophrenia is a complex mental disorders characterized by a wide range of cognitive,emotional and social impairments.Anhedonia is one of the core negative symptoms in schizophrenia and contributes to their functional outcome.However,it is still unclear about the underlying mechanism of anhedonia.Empirical findings have suggested that low-pleasure beliefs exist in both patients with schizophrenia and individuals with schizotypy,and these beliefs are correlated with anhedonia.Little is known about the underlying mechanisms of development and maintenance of these low-pleasure beliefs in both clinical and sub-clinical populations.It is also unclear whether belief updating process may impact on the formulation of such beliefs.In the present dissertation,we aimed to examine belief updating pattern of schizophrenia patients and individuals with schizotypy.The present dissertation comprised of three related studies to address such issues.In Study 1,we recruited 75 non-clinical college students.A modified belief updating task was designed and administered to these college students to examine the pattern of belief updating.The relationship between belief updating,beliefs about pleasure and anhedonia was also examined.Repeated-measurement ANOVAs showed that there was a significant interaction between Event type and News(F_?1,67?=4.789,p=0.032,?_p²=0.067).The subsequent analysis found there was unbiased belief updating for pleasant events?p=0.288?.However,for unpleasant events,the participants showed an optimistic bias in belief updating,that is they updated their beliefs to a greater extent in response to good news than bad news?p<0.001?.Furthermore,Partial correlation controlling for the differences in estimation errors,differences in memory and differences in number of trials showed that for pleasant events,there was marginal significance between the extent of belief updating in good news and the level of anticipating pleasurable activities;for unpleasant events,the extent of belief updating in bad news was marginally correlated with the level of devaluing pleasure.In Study 2,36 out-patients with schizophrenia and 30 demographically matched healthy controls were recruited to complete the same belief updating task administered in Study 1.Repeated ANOVAS analysis was conducted for pleasant events and unpleasant events independently.The results showed that for pleasant events,significant main effect was found in News(F_?1,58?=4.625,p=0.036,?_p²=0.074)and Group(F_?1,58?=5.421,p=0.023,?_p²=0.085),but there was no significant interaction effect between News and Group(F_?1,58?=2.924,p=0.093,?_p²=0.048).Subsequent analysis revealed,patients with schizophrenia tended to exhibit negative bias in belief updating?p=0.001?,specifically,compared with healthy controls,patients updated to a greater extent in response to bad news for pleasant events.However,for unpleasant events,there was no significant main effect and interaction effect in News and Group.Both patients and healthy controls updated to a greater extent in response to good news than bad news for unpleasant events.In Study 3,we administered the same belief updating task to 27individuals with schizotypy and 30 healthy controls to examine whether there was difference of the pattern of belief updating between them.We found that,similar to the pattern of belief updating in patients with schizophrenia,individuals with schizotypy also showed negative bias in belief updating only for pleasant events.However,there was no such a bias found in unpleasant events.Belief updating bias for pleasant events was also found to be negatively correlated with the level of attention to pleasure in individuals with schizotypy?r=-0.454,p=0.039?.Taken together,both patients with schizophrenia and individuals with schizotypy exhibited negative bias in belief updating only for pleasant events,but not for unpleasant events.These findings suggest that such a specific biased pattern may play an important role in the formation and maintenance of the low pleasure beliefs.Interventions targeting the pattern of belief updating is needed to provide a new perspective for the alleviation of anhedonia in patients with schizophrenia and individuals with schizotypy.