RESUMEN
Children are believed to construct their causal theories through talk and interaction, but with the exception of a few studies, little or nothing is known about how young children justify and build theories of the world together with same-age peers through naturally occurring interaction, Children's sensitivity to when a pair or group of interlocutors who interact frequently together feel that a justification is needed, is an index of developing pragmatic competence (Goetz & Shatz, 1999) and may be influenced by interactive goals and gender identity positioning. Studies suggest that salient contexts for justifications for young children are disagreement and control (e.g. Veneziano & Sinclair, 1995) but researchers have been less recognizant of 'situations in which partners verbally assist in the construction of justifications as a means to maintain contact or create solidarity' (Goetz & Shatz, 1999: 722) as contexts for justifications. The present study examined the spontaneously produced justification constructions in the naturally occurring free play of five friendship groups of preschool-aged children (aged from 3 ; 6 to 5 ; 4), in terms of the motivating context of the justification, marking of the causal relationship with a connective, and causal theories accessed in the talk. Partner expansion (validating justifications) was a salient motivating context for justifications, especially in the talk of friendship groups of girls, and seemed to privilege greater marking of the causal relationship with a connective and less arbitrary reasoning. One group of girls varied their use of validating justifications depending on the theme of play. Results are discussed in terms of the implications of use of validating justifications for children's causal theory building with peers, linguistic development, and pragmatic development.