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Traditionally, research on human stress has relied mostly on physiological and psychological measures with a relatively minor emphasis on the behavioral aspects of the phenomenon. Such an approach makes it difficult to develop valid animal models of the human stress syndrome. A promising approach to the study of the behavioral correlates of stress is to analyze those behavior patterns that ethologists have named displacement activities and that, in primates, consist mostly of self-directed behaviors. In both nonhuman primates and human subjects, displacement behavior appears in situations characterized by social tension and is likely to reflect increased autonomic arousal. Pharmacological studies of nonhuman primates have shown that the frequency of occurrence of displacement behavior is increased by anxiogenic compounds and decreased by anxiolytic drugs. Ethological studies of healthy persons and psychiatric patients during interviews have found that increased displacement behavior not only correlates with a subjective feeling state of anxiety and negative affect but also gives more veridical information about the subject's emotional state than verbal statements and facial expression. The measurement of displacement activities may be a useful complement to the physiological and psychological studies aimed at analyzing the correlates and consequences of stress.

Previous research has reported that a functional polymorphism in the monoamine oxidase A (MAOA) gene promoter can moderate the association between early life adversity and increased risk for violence and antisocial behavior. In this study of a combined population of psychiatric outpatients and healthy volunteers (N = 235), we tested the hypothesis that MAOA genotype moderates the association between early traumatic life events (ETLE) experienced during the first 15 years of life and the display of physical aggression during adulthood, as assessed by the Aggression Questionnaire. An ANOVA model including gender, exposure to early trauma, and MAOA genotype as between-subjects factors showed significant MAOA×ETLE (F1,227 = 8.20, P = 0.005) and gender×MAOA×ETLE (F1,227 = 7.04, P = 0.009) interaction effects. Physical aggression scores were higher in men who had experienced early traumatic life events and who carried the low MAOA activity allele (MAOA-L). We repeated the analysis in the subgroup of healthy volunteers (N = 145) to exclude that the observed G×E interactions were due to the inclusion of psychiatric patients in our sample and were not generalizable to the population at large. The results for the subgroup of healthy volunteers were identical to those for the entire sample. The cumulative variance in the physical aggression score explained by the ANOVA effects involving the MAOA polymorphism was 6.6% in the entire sample and 12.1% in the sub-sample of healthy volunteers. Our results support the hypothesis that, when combined with exposure to early traumatic life events, low MAOA activity is a significant risk factor for aggressive behavior during adulthood and suggest that the use of dimensional measures focusing on behavioral aspects of aggression may increase the likelihood of detecting significant gene-by-environment interactions in studies of MAOA-related aggression.

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The aims of this study were (i) to define the dimensions of non-verbal behaviour which distinguish between schizophrenic patients and control subjects and (ii) to examine the relationship between patients' non-verbal behaviour and clinical symptoms. The non-verbal behaviour of 28 drug-free patients with schizophrenia according to Research Diagnostic Criteria (RDC) and 25 control subjects was videotaped during interviews and scored according to an ethological scoring system. Patients' symptoms were rated on the Scale for the Assessment of Negative Symptoms, the Scale for the Assessment of Positive Symptoms and the Brief Psychiatric Rating Scale. As a group, schizophrenic patients showed a global restriction of non-verbal expressiveness, as indicated by their lower scores on prosocial behaviour, gesture and conflict. However, some patients had normal ethological profiles. Non-verbal behaviour was largely independent of negative and positive symptoms. Deficits in non-verbal behaviour may play a role in determining or aggravating dysfunctional patterns of relating in schizophrenia. Ethological analysis provides further support for the model that conceptualizes positive symptoms, negative symptoms and disorders of social relationships as three separate dimensions of the schizophrenic syndrome.