Effects of alcohol consumption and alcohol expectancy on the categorisation of perceptual cues of emotional expression

Evidence that alcohol leads to increased aggressive behaviour is equivocal and confounded by evidence that such effects may operate indirectly via expectancy. One mechanism by which alcohol consumption may increase aggressive behaviour is via alterations in the processing of emotional facial cues. We investigated whether acute alcohol consumption or the expectancy of consuming alcohol (or both) induces differences in the categorisation of ambiguous emotional expressions. We also explored differences between male and female participants, using male and female facial cues of emotional expression. Following consumption of a drink, participants completed a categorisation task in which they had to identify the emotional expression of a facial stimulus. Stimuli were morphed facial images ranging between unambiguously angry and happy expressions (condition 1) or between unambiguously angry and disgusted expressions (condition 2). Participants (N = 96) were randomised to receive an alcoholic or non-alcoholic drink and to be told that they would receive an alcoholic or non-alcoholic drink. Significant effects of alcohol were obtained in the angry-disgusted task condition, but only when the target facial stimulus was male. Participants tended to categorise male disgusted faces as angry after alcohol, but not after placebo. Our data indicate that alcohol consumption may increase the likelihood of an ambiguous but negative facial expression being judged as angry. However, these effects were only observed for male faces and therefore may have been influenced by the greater expectation of aggression in males compared to females. Implications for alcohol-associated aggressive behaviour are discussed.