motivation human 209 Humans 165 Motivation 141 male 131 female 129 adult 120 Female 81 article 75 Male 74 Article 69 controlled study 67 Adult 63 psychology 52 young adult 52 human experiment 47 Young Adult 43 adolescent 43 major clinical study 42 Adolescent 41 physiology 37 reward 34 middle aged 32 questionnaire 31 Middle Aged 29 Goals 26 Reward 26 decision making 24 clinical article 23 aged 21