Philip is correct. Forrest Gump had Aspergers Syndrome, aka Autism Disorder Syndrome 1 (ASD-1). Like most individuals with autism, he had difficulty communicating and navigating social situations. Although he was verbal, he had a language processing disorder that made his responses seem slow compared to a neurotypical person. He also interpreted figurative phrases people said to him literally, which is another characteristic of many Aspies. He had a pure, childlike heart, as many Aspies do. Despite his inability to communicate in social reciprocal manner, he was able to figure out the answers to problems through extreme tenacity and repetitive behaviors (i.e. running and running an running across the country, hanging in there with Lt. Dan despite his eschewing him, and staying out on the shrimp boat despite the storm). His purity and honesty are demonstrated when he gave half the money from the shrimp profits to Bubba's mother. He was able to do well despite his differences due to a kind mother who raised him well with a lot of social rules disguised as simple aphorisms to make the terrain of life easier to negotiate (i.e. "Life is a box of chocolates..."). He was also blessed with economic abundance and favorable conditions during his childhood, which shielded him from further trauma.