The behavior of laboratory animals demonstrates a mental experience wherein the animal's instincts tell it if it carries out a certain action, it will then receive what it needs. Primates regularly have sex in full view of infants, juveniles and younger members of their species. Engaging in homosexual behavior may allow species to obtain benefits such as gaining practice, relieving tension, and experiencing pleasure. It was the last film to receive the MPAA's X-rating due to its depiction of forced bondage and rape - however, it was re-rated and released as an NC film. However, the practice might have been a consequence of homosexual rearing, as the male orangutan in this dyad had had extensive same—sex experience. But if this artificial substitute is given to her a second season, she will not, as formerly, be content with it. Similar to humans, non-human animals also have a sensory system. There was an orgasmic response in 80 of the Japanese macauques studied. Lynch's screenplay was based on the novel by Barry Gifford, part one of a series of Sailor and Lulu stories, entitled Wild at Heart: In contrast, adult gorillas do not show any sexual interest in juvenile or infant members of their species. In a study comparing guinea pigs and humans, it was determined that the distress experienced by offspring separation in a guinea pig and a human going through depression activates the same region of the brain. The film eventually ended tragically for Junior.