ABSTRACT
Functional approaches to consciousness emphasize what it brings to behavior. Sensory awareness is one function. Normally it results from primary cortex stimulating higher levels of cortex, with reentry back to primary cortex. When primary cortex is destroyed, however, only pathways to secondary cortex remain. Absent reentry, "blindsight" or "deaf hearing" results, in which there is no sensory awareness even though residual vision or hearing is present.
Reentrant connections are a fundamental characteristic of the mammalian brain, existing in diverse species like monkeys, ferrets, and cats. Sensory awareness therefore dates back about 195 million years.
Metacognition, the awareness of one's own cognitive states and processes, is another function of consciousness. It includes "feelings of knowing" about one's level of knowledge. Old World monkeys show it, but New World monkeys yield ambiguous evidence, suggesting an origin about 45 million years ago.
Self-recognition is a third function. All great ape species can recognize themselves in mirror images. However, self-recognition is usually not immediate, and not all individuals show it. Old World and New World monkeys generally do not, although capuchins seem to know something is "different" about their image. Mirror self-recognition has been reported in scattered species, the successes usually though imperfectly accompanying encephalization.
A final function is theory of mind, the ability to impute mental states in oneself or others. Apparent successes can often be attributed to simpler mechanisms like stimulus-response association. Some observations resist such explanations, however: Among them, that chimpanzees detour to the end of a barrier to see what humans are looking at; and that they selectively retrieve food that a dominant rival can't see, in preference to what both can see. Referential pointing, helping, and deception have also been cited as demonstrating theory of mind . Again encephalization plays a role.
