Alcohol's influence leads one to respond more aggressively when provoked. Intoxication has long been presented as a mitigating factor to criminal behavior (see U.S. v. Garcia, The Forensic Echo (1) 1, pg 6). But is it so simple as a person's blood alcohol levels?
Researchers at the University of Pittsburgh and the University of Georgia found that alcohol had a two phase effect on human aggression. (J Abnormal Psychology 1997, 106:4, 598-607). Specifically, greater levels of aggression were found when blood alcohol concentration (BAC) increased, compared to when levels were declining. Also, subjects were more aggressive under conditions of high versus low provocation.
Sixty male social drinkers were assigned to one of four groups: alcohol level rising (AAL), alcohol level declining (ADL), or one of two sober control groups. Aggression was assessed in the AAL and ADL groups at respective ascending or descending EACs of 0.08%. The authors measured aggression using an aggression paradigm (S. Taylor, 1967), in which electric shocks were received from and administered to a fictitious opponent during a competitive task.
The degree of greater aggressiveness in the AAL group over the ADL was highly robust. No significant differences existed between the ADL group and the control groups, which indicates that alcohol does not appear to increase aggression on the descending limb of the BAC curve. This finding speaks against the theory that intoxicated aggression results directly from alcohol. If this were so, it could be argued that aggression should also have been seen with declining levels, because the subjects were still under the influence of alcohol at the time. Though individuals in the AAL group were more stimulated than sedated, and those in the ADL group were more sedated than stimulated, the differences were not significant.
The ascending level group was characterized by two features that have previously been linked to aggressive behavior: (1) increases in arousal and stimulation and (2) compromised neuropsychological functioning, specifically executive cognitive functioning (ECF). ECF encompasses higher order cognitive abilities such as attention, planning, organization, abstract reasoning, cognitive flexibility, and self and social monitoring.
The data elegantly illuminates the when and how of alcohol's impact on violent behavior. Increasing sophistication about the impact of alcohol assists the triers of fact to determine degree of responsibility as they frequently confront crime in the context of intoxication.
