In a previous paper (Braza et al., 1993) we quantified the social ability of pre-school children by means of two Indices: Amplitude of Behaviour (I.A.B.) and Amplitude of Partnership (I.A.P.). The aim of this study is to explore their possible relations with some agents of socialisation and to validate these indices of amplitude as a measure of social ability. The variables considered (biometrical measurements, family characteristics, and social behaviours in peer groups) were ordered by means of a prior analysis of the principal components, and the factor scores of each individual in these analyses were chosen as new variables. Twenty-six pre-school children attending a nursery in Cádiz (SW Spain) were filmed at school during their free-play period. Our results confirm the fitness of the Index of Amplitude of Behaviour (I.A.B.) not only as a useful tool for the study of socialisation, but also as a possible predictor of later success and social adjustment.