Alcohol and violence
Biochemical and psychological factors
It is established that alcohol produces dose-related changes in the brain, central nervous system and hormonal systems which in turn affect basic physiological and cognitive processes. After ingestion of moderate to high doses of alcohol, reaction times are generally slower; muscle control, dexterity and eye-hand co-ordination may be impaired; short-term and intermediate memory may be affected and performance on problem-solving tasks decreases.
Primary cognitive impairment
Pernanen (1976, 1991) and others have also shown that alcohol consumption interferes with primary cognitive ability by reducing the perceptual field. Steele and Joseph (1990) use the term 'alcohol myopia'. In layman's terms: when inebriated, we cannot 'take in' as much information from our surroundings and social context as we can when we are not inebriated. The information we use to guide our responses is increasingly limited in proportion to the amount of alcohol consumed. As inebriation increases, we begin to focus on small parts of the situation, one at a time, because our ability to perceive the situation as a whole is impaired. This in turn results in unstable, fluctuating perceptions and reactions, depending on which narrow aspect of our surroundings we are paying attention to. There is, therefore, an increased risk of misunderstandings and misinterpretations, which can in some contexts lead to aggressive responses.
Secondary cognitive impairment
Research has also identified secondary cognitive effects of alcohol on intellectual and linguistic ability (Pernanen, 1976, 1991; Gibbs, 1986). Quite simply, people who have consumed substantial amounts of alcohol have greater difficulty in thinking rationally and speaking clearly – making it harder for them to exercise sound judgement and substitute more acceptable behaviours, such as calm argument, for inarticulate aggressive responses. In some social contexts, it is easy to see how the combination of primary and secondary cognitive impairment – reduced ability to 'read' situations and behaviour and to respond rationally – could increase the potential for aggression and even violence.
It is equally clear, however, that this impaired ability to negotiate interpersonal relations does not inevitably, or even frequently, result in aggression or violence. The vast majority of people drink alcohol without becoming aggressive, and aggression and violence regularly occur in the absence of alcohol consumption. We outline here some of the processes by which alcohol-induced cognitive impairments may lead to aggression, but must stress that situational factors and cultural expectations regarding the effects of alcohol, discussed below, are the ultimate determinants of such behaviour.