child human 138 female 121 Humans 117 male 117 Child 103 Male 92 Female 91 adolescent 82 Adolescent 68 major clinical study 61 controlled study 58 adult 55 Article 54 article 48 psychology 45 preschool child 44 Child, Preschool 41 Adult 33 peer group 30 groups by age 29 young adult 29 Young Adult 28 Peer Group 26 child parent relation 25 human experiment 23 school child 21 infant 20 longitudinal study 19 physiology 19