Evolution of friendship and best friendship choices

It has been recognized in the literature that the mechanisms driving friendship choices differ when different settings are considered. At the same time, it is likely that different types of friendships are governed by different mechanisms.Employing longitudinal sociometric data from classrooms in elementary schools, it is examined whether gender similarity, reciprocity, and proximity (joint membership of study groups) have similar effects on 'friendship' and 'best friendship' choices.The results suggest that children use loose definitions of 'friendship', as opposed to their definition of 'best friendship'. The networks resulting from these different choices are found to evolve according to (partly) different mechanisms. This especially holds for the effect of gender similarity, which is profoundly predominant in the 'best friend' networks, but loses much of this importance when 'friends' are also considered. Also, 'best friend' choices are much more stable.Reciprocity of choices is found to primarily be a by-product of the preference to chose friends of the same gender, rather than being an important choice criterion of itself.