Females have displayed laterality of cradling and carrying their babies,while babies have also showed their nipple preference in primates.Some studies have demonstrated that the preference for laterality in primates is physically based on the asymmetry of their brain and the functional evolution process.The maternal cradling laterality and infant nipple preference in primates is regarded as an important topic in the study field on primates.However,this topic has not gotten much attention in China,yet.The results that got from the studies oversea have showed a variation from species to species in non-human primates.