Activity level as a dimension of temperament in toddlers: The validity of its measurement and its relevance for the organismic specificity hypothesis

The objectives of the present study were (1) to gather validation data on the activity subscale of the Toddler Temperament Questionnaire (Fullard, McDevitt & Carey, 1979), and (2) to follow up on hypotheses derived from earlier research on activity level as a possible mediator between environment and development. Of particular theoretical interest was the organismic specificity hypothesis which states that early experiences differentially influence development because the impact of the environment is mediated by individual differences in the organism. Subjects were 52 fifteen-month-old toddlers who were observed in their homes six times over a four week period. Data aggregated over these visits included actometer readings and measures of the caretaker's attention-focusing behaviors. Measures of the child's home environment and exploratory ability were also obtained. Correlational analysis revealed a zero-order relationship between actometer readings and questionnaire activity scores and moderate correlations among parent report measures. ANOVA analyses resulted in a significant interaction between activity level and intensity of stimulation in predicting both exploratory competence and total exploration. The findings provided clear support for the organismic specificity hypothesis. They also suggested that activity and temperament may be related to each other. Implications of the results for clinical work and future research on activity level and individual differences were discussed.