Cebus are a very cognitive species. They have expansive motor abilities, demonstrate a high level of proficiency in using tools to obtain food; and play, using thoracic members. Our objective in this work is to study the shoulder and arm muscles of Cebus genus, comparing the findings with the literature data on humans, chimpanzees and baboons, and assume these aspects are associated with behavioral characteristics. We conclude that the shoulder and arm muscles of Cebus, in general terms, are more similar to baboons, perhaps due to the quadruped behavior exhibited in these animals. The conventional term “hand abilities” in primates, specifically in Cebus, originate in motor abilities, generally, from thoracic members. They are controlled by a high encephalic index, and not by specific motor abilities from the intrinsic muscles of the hand and forearm which act on the hand.