The Brain Mechanism Of Positive Outcome Expectation For Aggression And Its Relationship With Proactive Aggression

Proactive aggression is one kind of aggressive behavior,which is usually cold,deliberate,and goal-directed,on the purpose of attaining a goal(material or territorial acquisition or social domination),which could occur without external provocation.Proactive aggressive behaviors may cause a lot of harm,ranging from the small impact on individual safety,health and life happiness to the large impact on the long-term stability of the country and society.Therefore,the research on proactive aggression has always been the focus of psychological researchers.The generation of proactive aggression is usually driven by the expectation of positive consequences,which is aggressive or premeditated in nature.The main and key cognitive mechanism of proactive aggression is aggression outcome expectancy,especially positive outcome expectancy for aggression,such as reward anticipation.Positive outcome expectancy for aggression refers to the expected positive outcome of the aggressive behavior.It is one kind of cognitive assessment,which is subjective.According to the Social Information Processing Theory and the Expectancy-Value Theory,a person's expectation could have a great impact on subsequent behavior.If individuals expect aggression can bring more positive results,they are more likely to make proactive aggression.Therefore,it is meaningful to explore the relationship between positive outcome expectancy for aggression and proactive aggression.Although there were many empirical studies about outcome expectancy for aggression and proactive aggression,there were still some deficiencies in these studies.For example,the brain association of the expected positive outcome and its relationship with proactive aggression were not clear.Therefore,this study,on the basis of relevant theories and previous studies,combined with FMRI technology,preliminarily explored the brain association of positive outcome expectancy and its relationship with proactive aggression through two studies.In Study 1,the voxel-based morphometric analysis(VBM)was carried out on 202 undergraduate students(126 female students and 76 male students,the average age of them was 20.95 years old,with a standard deviation of 1.62 years old and an age range of 18-33 years old)to reveal the anatomic basis of the expected positive outcome of aggression in daily life and its relationship with proactive aggression.All theparticipants were right-handed and were required to complete the Social Emotional Information Processing Assessment for Adults and Reactive-Proactive Aggression questionnaire,and all of them conducted FMRI scans.The results showed that the aggression positive outcome expectancy was significantly positive correlated with the grey matter volume in the left precuneus(x =-18,y =-51,z = 51,cluster size= 270,t =4.60,p < 0.05).The aggression positive outcome expectancy mediated between the grey matter volume in the left precuneus and proactive aggression.In Study 2,Study 2A and Study 2B were included.We did the laboratory experiment to investigate the causal relationship between reward expectation(positive outcome expectancy for aggression in the laboratory)and proactive aggression and its underlying brain activation mechanism by referring to the probabilistic monetary incentive delay task(classic reward expectation task)and reward-harm task.Study 2A was a preliminary experiment(behavior experiment),in which 15 participants,including 7 males and 8 females,were recruited,ranging in age from 18 to 22 years old(M= 19.66,SD=1.08).The results showed that by changing the different monetary amount via aggression and the probability of gaining the monetary rewards,we successfully manipulated the expected value of the aggression(There was a significant difference between the high reward valence expectation of aggression and low reward valence expectation of aggression,t=108.51,p<0.001)and the expected probability that the attack could bring reward(There was a significant difference between the high expected probability of reward acquisition for aggression and low expected probability of reward acquisition for aggression,t=196.66,p<0.001).Study 2B was a formal experiment via task FMRI,in which 37 participants were recruited,including 17 males and 20 females,ranging in age from 18 to 23 years old(M=20.8,SD=1.42).In specific,we manipulated the amount of money(Low amount: 0.5-1.5 yuan;High amount:10.5-11.5 yuan)that may be obtained through aggression with a certain probability(Low probability: 10%-30%;High probability: 70%-90%)to investigate the effects of aggression-related reward valence expectation(Low,High)and reward possibility expectation(Low,High)on the induced proactive aggressive behavior and explored its underlying brain activation mechanism.We found that the brain activation areas associated with the expected reward through aggression mainly involved the lingual gyrus,inferior temporal gyrus,precuneus,caudate nucleus,inferior frontal gyrus,cingulate gyrus,anterior central gyrus and posterior central gyrus and so on.Brain activation associated with aggressive reward anticipation of the left insula,left medialfrontal gyrus,left thalamus,and right medial frontal gyrus were related to proactive aggression.The brain activation areas of proactive aggression induced by reward expectation mainly involved the insula,inferior frontal gyrus,inferior temporal gyrus,pallidus,caudate nucleus and so on.Based on two studies,we drew the following main conclusions:(1)Both in everyday life and in a lab setting,the expected positive outcome of aggression was closely related to proactive aggression in emerging adulthood.(2)The expected positive outcome of aggression was closely related to the left precuneus.The larger the gray matter volume in the left precuneus was,the stronger the individuals expected the positive outcome of aggression,and the higher level of proactive aggression the individuals made.(3)Individuals showed higher level of proactive aggressive behavior under the high aggression-related reward expectation(high aggression-related reward valence expectation and high aggression-related reward acquisition possibility expectation).Aggression-related reward anticipation was involved in the brain activation of reward and social cognition,which was related to reward-induced aggressive decision-making.This study filled in the gap of the brain association between positive outcome expectancy and proactive aggression,and provided basis and reference for the prevention and intervention of proactive aggressive behavior.