Potentiation may be exclusively a phenomenon of the feeding system, and its general importance for learning and memory might therefore be quite limited ( Lett, 1982; Rusiniak, Hankins, Garcia, & Brett, 1979). The core of this argument has been that the clearest instances of potentiation have taken, exclusively, a singular form presence of a distinctive taste has enhanced the conditioning of another element. The letter typically has been an odor or another taste, but not always (e.g., Galef and Osborne, 1978, found that taste potentiated conditioning of a visual stimulus).
The idea that potentiation is exclusively a feeding phenomenon has provided the framework for a particularly thorough set of experiments by Lett ( 1982), who calls the phenomenon "associative potentiation." In this view, the strength of the association between a CS (conditional stimulus) element and an illness is said to be enhanced in an absolute sense, in and of itself, because of the presence of another element -- explicitly a taste -- in the CS compound.
Lett's explanation is based on the general notion that the association between gustatory and visceral consequences, between a taste and a sickness, involves a special learning system that is phylogenetically old and can be seen in essentially all animals. Potentiation is viewed as synonymous with absolute strengthening of an association between a sickness and a stimulus feature such as an odor (or color) that ordinarily would not be readily associated with sickness, due to the presence of a taste in compound with that feature. The presence of the taste potentiates this association by endowing the odor with properties of the taste. In this view also, potentiation of the learning of odor by the presence of taste is particularly adaptive because odor is a distal cue that controls a different response component of feeding than does taste, the more proximal cue. Presumably the economy of behavior is therefore enhanced because upon sensing the conditioned odor, the animal can terminate its foraging for a substance to which taste aversion has been conditioned. Similarly, if a preference is conditioned to a taste, the potential conditioning of odors paired with that taste will result in more rapid approach to the substance involved.
This explanation has been subjected to an experimental analysis by Lett ( 1982) that is both broad and thorough. Her results are impressive. Potentiation would seem quite well suited as a special adaptation for feeding. But it is uncertain whether potentiation has generality beyond feeding per so and whether the mechanism for potentiation is always, or ever, an absolute strengthening of the association between the potentiated CS element and the US (unconditional stimulus). We present experiments that address both of these uncertainties. Our date will question the exclusivity of feeding for potentiation by showing that potentiation can occur in conditioning circumstances where ingestion is not involved, and when ingestion is central to the conditioning, potentiation sometimes occurs but sometimes does not, depending on other factors. Our data will also