以停止訊號作業檢視暴力行為者的抑制機制

The nature of altered inhibitory control in impulsive violent offenders

暴力行為造成了嚴重的社會問題。重愎性的暴力犯罪者常常是在抑制歷程上發生問題。本研究以暴力成年犯為主要研究之對象，為了瞭解他們攻擊行為背後的成因，採用追蹤方式的停止訊號作業，比較暴力成年犯（實驗組）與非暴力行為組（控制組）在抑制控制的行為表現差異。在進行受試者分類上，除了從過去犯罪史篩選受試者，亦採用反應性－主動性暴力行為問卷來進行分類。如果衝動型暴力行為的機制，可能是因為有過強的衝動傾向，有較高的行為激發系統（behavioral activation system）活化程度，暴力犯的go反應時間應該較控制組更快。相反的，若衝動性暴力犯是因有較低的行為抑制系統（behavioral inhibition system）活化程度，暴力犯的停止信號反應時間（stop signal reaction time,SSRT）應該較控制組更慢，是抑制能力缺損的結果。本實驗設計方式是透過對於go刺激有更快的反應速度和產生接近50%的抑制失敗錯誤率，在這樣的情況下，受試者需要投入更多的抑制控制來強列的go反應傾向，而這對衝動性暴力犯可能更加的困難。研究結果顯示實驗組的行為樣態偏向衝動型暴力行為，實驗組的SSRT顯著地比控制組長，他們抑制自己行為的能力可能較差，無法有效調控負面情緒，降低其抑制能力，導致犯下更多的錯誤。

Violent behavior often causes serious social problems. Repeated violent offenders are frequently described as having impairments in inhibitory control. In this study, a tracing method of the stop - signal task was used to examine inhibitory control in offenders with impulsive violent behavior compared to those without violent behavior. Subjects were categorized not only based on past criminal history, but also on reactive Proactive Aggression Questionnaire score. Impulsive violent behavior could be a consequence of either a greater tendency to generate pre - potent responses or a deficit in inhibition of such responses. If we consider that violent offenders may be characterized by higher behavioral activation system activity, the go RTs of violent offenders on a stop signal task would be expected to be lower than controls. In contrast, if violent offenders are characterized by lower behavioral inhibition system activity, the SSRT of violent offenders, which indexes inhibitory control, might be expected to be longer than for controls. Furthermore, the task design may cause the subjects to develop an impulsive response style characterized by faster reaction times to go stimuli and maintain close to 50％ unsuccessful inhibited responses. In such a situation, the subjects need to recruit more inhibitory control to overcome the stronger go response tendency. The results showed that the impulsive violent offenders made more errors on stop trials and their SSRTs were significantly longer than matched controls. This study shows impulsive violent offenders may not be able to regulate negative emotions arising as a result of errors or use such error information to adjust their behavior effectively, resulting in more errors being committed.