Within pschology there is a debate between dualists and monists over whether the mind and the brain are "seperate and distinct entities". Dualists believe that the brain and the mind indeed are seperate entities whereas monists believe that the mind and brain are the same thing. This is emphasized by the psychoneural identity hypothesis, which states that while we might find it convenient to distinguish certain types of mental activity for semantic purposes, all experience is, in principle, completely reducible to physical activity within the brain. In practice we are a long way from being able to carry out this reduction due to the sheer complexity of the brain, but in principle the orthodox scientific view believes this is possible.
Discussion of the psychoneural identity hypothesis is relevant for all disciplines concerning themselves with theories of cognition (such as Interaction Design/HCI). As an example, it is relevant for the field of Artificial Intelligence in that it, if accepted, provides support for the claim that intelligent behaviour can emerge from mere information-processing systems like computers. If an entity (the human mind) is merely a sum of its parts (neurons), it can be argued that other systems are likewise reducible to the sum of their constituent parts. Consequently, the hypothesis implicitly questions whether a system (organic as well as mechanical) can display properties that are not merely a sum of its elements, a statement which, pushed to extremes, would render disciplines such as psychology and sociology superflous if neurobiological advances were made.