human motivation Humans 165 Motivation 134 female 126 male 121 adult 115 Female 80 Male 72 article 71 Adult 63 Article 60 controlled study 58 psychology 52 young adult 52 human experiment 47 Young Adult 43 adolescent 43 major clinical study 42 Adolescent 41 physiology 35 middle aged 32 questionnaire 30 Middle Aged 29 reward 29 Reward 26 Goals 24 clinical article 23 decision making 22 aged 21