Phenylacetic acid production in dominant and non-dominant vervet monkeys.

Free and conjugated plasma phenylacetic acid concentrations were significantly higher in dominant male vervet monkeys than in non-dominant males living in stable social groups. These findings may be connected with an earlier observation that plasma from aggressive human psychopaths contains higher concentrations of phenylacetic acid than non-aggressive controls; whether they reflect an increased production of phenylethylamine is still unknown.