Psychology
Split Brain and UX Research
CGP Grey came out with a video in mid 2016 about how your brain can act as two, siting experiments from epilepsy treatments where the connection between two halves of the brain were cut.
This brings up a specific issue that can be encountered in user interviews and is the reason you do not simply ask what the user wants. They do not truly know. They have a need that they try to explain the reasoning for, but often do not understand the core motivation that is driving a specific desire for a feature. It is important to instead focus on what they user does, it is a more accurate measure to determine what their real needs are and features that would best address and satisfy those needs.