Harry Frederick Harlow ( October 31 , 1905 - December 6 , 1981 ) was an American psychologist best known for his maternal-separation , dependency needs , and social isolation experiments on rhesus monkeys , which demonstrated the importance of care-giving and companionship in social and cognitive development .
Harry Frederick Harlow ( October 31 , 1905 - December 6 , 1981 ) was an American psychologist .