Paradoxical effects of hedonic disparities in negative anticipatory contrast.

Negative anticipatory contrast (NAC) occurs when the presentation of two solutions in sequence over a number of trials leads to the suppression in consumption of the first solution. A hedonic 'disparity' between the two solutions may lead to this suppression. However, what the relative role of the gustatory properties versus the nutricaloric loads of the two solutions is in determining the acquisition of NAC is uncertain. Previous experiments have typically used saccharine and sucrose solutions, which resemble each other in gustatory properties yet differ in their nutricaloric loads. In contrast, the present experiments used soy milk and sucrose solutions, which are both highly nutritive but differ in their gustatory properties. Soy milk was found to have a higher hedonic value than a 16% sucrose solution as measured by both choice and absolute consumption. According to a hedonic disparity hypothesis, NAC should have occurred using a sucrose-soy sequence but not a soy-sucrose sequence. Paradoxically, the sucrose-soy sequence failed to yield NAC, but the soy-sucrose sequence did yield a repeatable, significant NAC. A consideration of the available theory and research indicated that NAC may be explained by a strong conditioning of a satiety response produced by sucrose that opposes the conditioning of sucrose's positive hedonic response.