The reason why children become "doves" - cautious and submissive when confronting new environments, or "hawks" - bold and assertive in unfamiliar settings has been explained by researchers.
Researchers say these basic temperamental patterns are linked to opposite hormonal responses to stress - differences that may provide children with advantages for navigating threatening environments.
"Divergent reactions - both behaviourally and chemically - may be an evolutionary response to stress," Patrick Davies, professor of psychology at the University of Rochester and the lead author of the study, said.
"These biological reactions may have provided our human ancestors with adaptive survival advantages. For example, dovish compliance may work better under some challenging family conditions, while hawkish aggression could be an asset in others," he stated.
This evolutionary perspective, says Davies, provides an important counterpoint to the prevailing idea in psychology that "there is one healthy way of being and that all behaviours are either adaptive or maladaptive".
Co-author Melissa Sturge-Apple agreed: "When it comes to healthy psychological behaviour, one size does not fit all."
The study was published online July 8, 2011, in Development and Psychopathology.