Development of learned food aversions in humans: investigation in a "natural laboratory" of cancer chemotherapy.

Humans often develop learned food aversions (LFAs) to foods or beverages consumed in temporal contiguity to gastrointestinal distress. Viewed as a classical conditioning process, principles of LFA development have been studied in the animal laboratory. Cancer chemotherapy provides a "natural laboratory" for examining whether these principles characterize human LFA development. Chemotherapy patients (n = 63) were interviewed prior to a regularly scheduled chemotherapy infusion (i.e. target infusion). Foods and beverages consumed in the preceding 24 h were identified. Postinfusion nausea and vomiting (PNV) was assessed. Finally, preference changes for items consumed prior to the target infusion were assessed prior to patients' next chemotherapy infusion. Contrary to hypothesis, (a) less preferred and familiar items were not more likely to become LFA targets, (b) LFA items were not consumed in close temporal contiguity to either the initiation of chemotherapy or PNV, and (c) LFAs developed in the absence of PNV. Consistent with the hypothesis, the severity of PNV was associated with a greater likelihood of LFA development. Problems in defining LFAs under non-experimental conditions are discussed as are the implications of results for the classical conditioning model of human LFA development.