Anxious Responses To Predictable And Unpredictable Aversive Stimuli And Relevant Peripheral Physiological Mechanism

Anxiety is an emotional experience shared by both humans and animals in the face of dangerous circumstance and it is also a defensive response to unpredictable threatening events.A lot of studies have shown that the unpredictability of aversive stimuli is a key factor in inducing anxiety.However,relevant studies at present mainly focus on the impact of predictability on anxiety and there is no systematic study on the characteristics of predictability.Therefore,this study mainly discussed the effect of different levels of predictability on subjective anxiety of individuals and the relationship of the two sub-characteristics of predictability-the occurrence probability and randomness as well as their influence on anxiety and fear.The first study investigated the effect of the predictability of aversive stimuli on individual subjective anxiety and physiological arousal induced by the adapted probability task.Experiment 1 used behavioral experiments to investigate the effect of different levels of predictability on individual subjective anxiety.Results indicated that the self-reported anxiety was highest during the probability interval of 40%-60%.Experiment 2 explored whether the effect of the predictability of aversive stimuli on anxiety was modulated by the intensity of the stimuli.The results showed that the effect of predictability on anxiety was regulated by the intensity of aversive stimuli in the emergence of aversive stimuli,and that the effect of predictability on anxiety increased linearly from the no-threat to the moderate aversive stimuli to the high intensity aversive stimuli.In the cue period,the effect of predictability on anxiety was not regulated by the stimulus intensity,and individuals showed greater SCR to the threat cue in the low predictable condition.The results showed that the intensity of stimulation can affect the individual's fear rather than anxiety,and predictability is intrinsically associated with anxiety.In the second study,the effect of two sub-characteristics of predictability:the effects of the probability of occurrence and randomness on anxiety were investigated by combining behavior(Subjective reports)and physiological indicator(skin conductance responses).Experiment 3 showed that the influences of the two characteristics of predictability on anxiety were not independent,but interdependent.SCR results showed that SCR during cues and the exposure period of aversive stimuli were significantly greater under the conditions of higher random probability and lower regular probability than those under the conditions of higher regular probability and lower random probability.Furthermore,we guessed that individuals may have developed a sense of learned helplessness under the conditions of lower predictability.