Edited sentence: Building on the earlier work on temperament of Stella Chess, Kagan rejected almost every assumption on which attachment theory etiology was based, arguing that heredity was far more important than the transient effects of early environment, for example a child with an inherent difficult temperament would not illicit sensitive behavioural responses from their care giver.Concern about attachment theory has been raised with regard to the fact that infants often have multiple relationships, within the family as well as in child care settings, and that the dyadic model characteristic of attachment theory cannot address the complexity of real-life social experiences.Following the argument made in the 1970s that attachment should not be seen as a trait (lasting characteristic of the individual), but instead should be regarded as an organising principle with varying behaviours resulting from contextual factors, later research looked at cross-cultural differences in attachment, and concluded that there should be re-evaluation of the assumption  that attachment is expressed identically in all humans.Harris and Pinker have put forward the notion that the influence of parents has been much exaggerated and that socialisation takes place primarily in peer groups, although H.Harris, Stephen Pinker and Jerome Kagan are generally concerned with the concept of infant determinism (Nature versus nurture) and stress the possible effects of later experience on personality.Recent critics such as J.Rudolph Schaffer concludes that parents and peers fulfill different functions and have distinctive roles in children's development.Subsequent research has not bourne out  Kagan's argument and broadly demonstrates that it is the caregivers behaviours that form the child's attachment style although how this style is expressed may differ with temperament.The debate spawned considerable research and analysis of data from the growing number of longitudinal studies.Various studies appeared to show cultural differences but a 2007 study conducted in Sapporo in Japan found attachment distributions consistent with global norms using the six-year Main & Cassidy scoring system for attachment classification