Learning without Memory.

After a CS-US learning trial, powerful feedback (FB) selectively modulates the hedonic value of the US, perhaps affecting the CS as well. FB. operates regardless of the subject's attributions or awareness, often influencing the subject's unconscious motives in a single trial. Most of the evidence comes from feeding research where the taste US and the internal FB are independently manipulated, but similar influences are at work with painful, thermal and sexual USs in a wide variety of species including humans. Implications for cognitive theorizing and neural research on mechanisms of learning are discussed.