The Phylogenesis of the “Ego,” with Remarks on the Frontal Lobes

Ego, Ich, I, whatever the language, this clipped, easily articulated word designates an inner state, well-recognized in consciousness, referring not only to what is identified as self, but also to the awareness of self as agent. In current mental science, the term ego is preferred. Despite its clear recognition subjectively and the fact that its derangements may be observed by others, quotation marks enclose this term in the title to indicate its metaphorical nature. The ego cannot be precisely defined or compartmentalized.

Since, despite its metaphorical nature, the ego designates a recognized mental function, it has an underlying biological structure and history. In the mental sphere, where there is no tangible fossil record, phylogenetic reconstruction is speculative. Nevertheless, such speculation may clarify the concept of the ego.

Approach and avoidance reactions are demonstrable in all motile organisms beginning at the unicellular level. Such reactions clearly have adaptive necessity for interplay with stimuli and objects outside the organism's own anatomical borders. Individual and species enhancing stimuli or objects evoke an approach reaction; injurious ones an avoidance reaction. When a requisite level of neural complexity is gained, it is likely the approach reaction becomes endowed with an inner feeling tone best called pleasure and the avoidance reaction with the feeling tone of pain. Infrahuman organisms do not have the apparatus to report their inner states, but the work of Olds and Olds (1963) has demonstrated approach and avoidance behaviors in rats related to reward and aversive loci in the rat brain. We assume that in complex organisms, there is some subjective accompaniment.

At the unicellular and at the level of simpler nervous systems, approach-avoidance reactions appear to operate at a “reflex” level so that a noxious stimulus or object automatically evokes an avoidance movement, the