motivation 259 human 233 Motivation 220 Humans 185 male 148 female 144 adult 136 Female 89 Male 82 article 82 Article 78 controlled study 78 Adult 69 psychology 57 young adult 53 human experiment 51 adolescent 47 major clinical study 47 Adolescent 45 Young Adult 44 physiology 38 middle aged 37 reward 36 Middle Aged 34 questionnaire 32 Reward 27 Goals 26 clinical article 25 Employee motivation 24 decision making 24