Researchers know relatively little about the normative development of children's behaviors aimed at alleviating distress or discomfort in others. In this article, the authors aim to describe the continuity and discontinuity in the degree to which young children in the general population are reported to exhibit specific prosocial behaviors. Data came from the Québec Longitudinal Study of Child Development. Consistent with Hay's model of prosocial development, the results show that there were about as many children who stopped exhibiting prosocial behaviors between 29 and 41 months of age as there were children who started doing so during this period. Further, gender differences (girls > boys) in prosocial behaviors are either emerging or at least increasing in magnitude, with girls being more likely to start and boys being more likely to stop exhibiting these behaviors between 29 and 41 months of age. Consistent with the early-onset hypothesis, children who exhibit prosocial behaviors at 17 months of age are less likely to stop exhibiting the same behaviors between 29 and 41 months of age. Otherwise, if they did not exhibit prosocial behaviors at 29 months of age, they are also more likely to start doing so in the following year.

We know relatively little about the development of disruptive behaviors (DBs), and gender differences therein. The objective of this study was to describe the continuity and discontinuity in the degree to which young children in the general population are reported to exhibit specific DBs over time. Data came from the Québec Longitudinal Study of Child Development. First, the results show that relatively few children exhibit DBs on a frequent basis at 41 months of age. Second, the results show that a majority of children who exhibit a particular DB on a frequent basis at 41 months of age did not do so 1 year earlier. In addition, a majority of children who exhibited a particular DB on a frequent basis at 29 months of age no longer do so 1 year later. Third, gender differences in DBs (boys girls) are either emerging or at least increasing in magnitude between 29 and 41 months of age. Consistent with the canalization of the behavioral development principle, children who exhibited DBs on a frequent basis at 29 months of age are less likely to stop doing so in the following year if they had exhibited the same behaviors at 17 months of age.

Quatre autre études épidémiologiques longitudinales furent recensées, toutefois elles ne comportent pas de mesure de l'agression physique valable pour les fins de notre étude. En effet, l'étude anglaise de Jenkins Owen, Bax et Hart (1984), tout comme l'étude norvégienne de Mathieson et Sanson (2000) n'inclue pas de mesure de l'agression physique. De plus, l'étude américaine de Briggs-Gowan, Carter, Skuban et Horwitz ( 2001) utilise une mesure qui comporte différents types de comportements extériorisés. Finalement, l'étude néerlandaise de Koot, Van Den Oord, Velhulst et Boomsma (1997), bien qu'elle comporte une mesure de l'agression physique, ne permet pas l'élaboration de conclusions pertinantes à notre propos.