As time went by and the monkeys grew, Harlow was also able to study the effects of maternal deprivation. In the following experiments, Harlow placed the monkeys isolated from each other during the first eight months of life. He restrained them from having any contact with each other or any contact with the substitute mother. These monkeys were damaged permanently. They behaved in a strange way. The monkeys sat and began rocking back and forth constantly. This is a stereotypical pattern for aggressive behavior. These monkeys also showed differences in their sexual behavior. Isolated female monkeys never made an attempt to approach normal males. Whereas isolate males made aggressive attempts to mate with normal females. Harlow also tested the
