The author argues that the reason creative people exhibit these features is because of cognitive disinhibition.
Cognitive disinhibition is the failure to ignore information that is irrelevant to current goals or to survival. We are all equipped with mental filters that hide most of the processing that goes on in our brains behind the scenes. So many signals come in through our sensory organs, for example, that if we paid attention to all of them we would be overwhelmed. Furthermore, our brains are constantly accessing imagery and memories stored in our mental files to process and decode incoming information. Thanks to cognitive filters, most of this input never reaches conscious awareness.
This is less active in creative people, meaning they actually experience more of the world. As noted, this can be overwhelming. It is not uncommon for artists to be overwhelmed -- and to thus go crazy. Most stay sane by funneling it into their creative works. The occasional voices become characters in a story and are thus controlled, tamed. Thus, the ability to control one's thoughts is a necessary part of the creative process. One needs self-control and discipline as much as cognitive disinhibition to make art and literature.
One must wonder, however, what effect, if any, this has on the reader. Or how understanding this might affect our understanding of an artist's works. How should this affect the way we analyze works?