[The genetics of child temperament]

In spite of the high initial expectancy in preliminary results concerning the genetics of personality, these studies have not provided satisfactory results. The failure could be related to the lack of biological validity of personality concept and the important influence of environmental factors on personality. A possible way to solve this problem is to look at the temperament of preschool children. It is expected that variability in infants' behaviour can be better defined and with less environmental influence.

Firstly, twin and adoption studies of child temperament in comparison with the studies of personality in adults are reviewed. Secondly, the molecular association studies carried out concerning child temperament are analyzed. The serotonin transporter gene (5-HTT), D4 receptor gene (DRD4) and mono amino oxidade-A gene (MAOA) have been considered candidates to explain variability in child temperament because these genes have been related with specific personality dimensions and mental diseases. Finally, the methodological problems and the future direction of research in this field are considered.

Heritability shows higher values in infant temperament than in adult personality. Different gene polymorphisms on 5-HTT, DRD4 and MAOA could explain some individual variability in children's behavior, although replication studies are needed to confirm the role of these genes. Longitudinal studies in large samples that include gene and environmental interactions are one of the best ways to improve our knowledge about the genetics of child temperament.