António J. Santos holds a degree in Clinical Psychology from ISPA and a PhD in Development Psychology from the Université du Quebec in Montreal, Canada. He was visiting professor at the Department of Human Development and Family Studies, Auburn University, USA. He was leading investigator in several FCT funded projects and a founding member of the Portuguese Societies for Ethology and Primatology, and is a member of the Society for Research in Child Development amongst others. He published in several national and international scientific reviews, namely Child Development, Developmental Psychology, Social Development, International Journal of Primatology, Merril Palmer Quarterly amongst others. He as presented papers at the most important international conferences, relating to his area, having also been invited for giving Key note addresses and organizing symposiums in his specific field of investigation. He consulted on several international investigation projects, namely in Canada and the USA. His major area of research is the study of peer relations in child and adolescent social development. My major research objective is to complement traditional psychological individual differences approaches to children’s social status and social competence with a broader socio-ethological understanding of the impact of local affiliative niches (e.g. friendship relationships, affiliative subgroup membership) emerging from the social ecology and organization of the peer group.