Which famous greek philosopher wrote extensively about psychological topics such as sleep and dreaming, the senses, memory, and learning?

One day you learn that this same wealthy friend has become active in a community organization that serves the mentally challenged and their parents. you are told that her work with mentally challenged children consumes most of her weekends and a substantial part of her income and that she lives in modest circumstances. you find this hard to believe, and you suspect that somehow she is profiting from her involvement.