Each developmental stage becomes a rung on the ladder and in a healthy aging progression, each rung on the ladder will have been experienced. When humans miss a rung, or bypass a stage in psychological development leaving transitional problems unresolved, the repercussions manifest themselves typically in adulthood. For example, if a child loses a parent at a young age, a deficit can develop. The child, as an adult, may become a parent. Prosen has done extensive research and has worked with patients to repair such a transitional deficit.
People try to pick up where they left off.
The deficit surfaces as a problematic issue and the issue must be recognized and then dealt with at that time. With bonobos, the unresolved lifestage can be recreated. Prosen tried to recapitulate the missing development through a past-track catch up. But Prosen's work with Brian for the past several years hasn't been as simple as putting an ape at the bottom of a ladder. After all, bonobos have the closest genetic make up to humans than any other mammal.