Temperamental differences, family relationships, and young children's response to change within the family.

In a longitudinal study of 40 firstborn children, temperamental differences between the children were found to be linked to the emergence and persistence of anxious and unhappy behaviour over the year following the birth of a sibling. Direct observation showed that these temperamental differences were also associated with differences in the children's interactions with their mothers, and with differences in their behaviour towards their mothers when mother and sibling were interacting. In contrast, the wide range of individual differences in the behaviour of the firstborn children to their siblings was not associated with temperamental difference between the children. There was some evidence for continuity in temperamental differences between the assessments before and after the sibling birth, but in many children the behavioural changes were marked. These findings underline the clinical significance of temperamental differences in children's vulnerability to changes in family life; they also indicate that 'temperament' should be considered not as a characteristic of the child independent of his or her particular family relationships but, on the contrary, as closely linked to his or her relationship with the mother, and as susceptible to the effects of marked change in the family environment.