Preface: sex differences in the functions and precursors of adolescent aggression

Over the last two decades, the gap betweenadolescent girls’ and boys’ involvement in aggressivebehavior has steadily decreased. Statistics on violentcrimes committed by adolescents [Puzzancheraet al., 2003] and self-report measures of offending[US Department of Health and Human Services,2001] indicate the ratio of girls to boys involvementhas decreased 3-fold over the last 20 years. Whilegirls’ involvement in violence has yet to ‘‘reach thehigh water mark set by male violence’’ [Alder, 1975;p 14], such trends have sparked volumes of newresearch documenting sex differences in the magni-tude and expression of aggression at differentdevelopment periods. Over the past two decades,for example, the number of papers published on sexdifferences in childhood or adolescence aggressionhas increased an average of 3.4% per year, resultingin an accumulated increase of 616 peer-reviewedpapers during that time