Dictionary.net

The science of the connection between nerve action and consciousness; the science which treats of the relations of the psychical and physical in their conjoint operation in man; the doctrine of the relation of function or dependence between body and soul.

The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship.

Science of the relations of mental processes to their causation and manifestations.

The science of the relations of physical nerve stimuli to the psychical sensations they produce. [Gr.]