[Izzy Dunne]

Medical research has indicated that people like schizophrenics

Some research. I doubt that very much.

[oblomov]

Agreed. Is there a precise, experimentally-validated definition of “self talk”?

[hinckley buzzard]

There is a continuum from external to internal that characterizes cognition, behavior, and perception. At threshold levels, it has been shown that perfectly normal people can err in differentiating between an external stimulus, a low volume tone, say, and a corresponding imagined one. Under certain conditions, this kind of error can occur at more intense levels, such that words which are thought can be mistaken for being actually heard--"hearing voices."

By the same token, under high levels of arousal, a person who is absorbed in thinking may find himself actually verbalizing his thoughts unintentionally--"talking to himself."

Many other symptoms of mental illness can be understood similarly as normal functions carried to excess.

This research btw goes back to the early twentieth century, when people took the scientific study of psychology seriously.