title: Neither extended sequential nor simultaneous feature positive training result in modulation of evaluative flavor-flavor conditioning in humans.
abstract: In previous attempts to induce Pavlovian modulation of human evaluative flavor-flavor associations, the recurrent finding was that exposure to a Feature Positive (FP) schedule (XA+/A-), in which flavor A was reinforced by the aversive flavor Tween20 if and only if it was accompanied by a feature stimulus X, did not result in the expected X-modulated dislike for target A, but in simple unconditional A-US associations. The first experiment reported here investigated if more extended training results in a shift from simple A-US learning to the development of X-modulated A-US associations. Participants were exposed to a 32-trial, 4-session sequential FP schedule using flavors both for feature and target stimuli. The modulatory and/or excitatory power of the stimuli was assessed after each training session. After initial training, participants again acquired a simple unmodulated target A-US association. Contrary to expectations, the additional training sessions did not result in participants gradually learning the XA+/A- discrimination, but rather seemed to corroborate the already established A-US association. This was true whether or not participants acquired valid explicit knowledge about the conditional X-->(A-US) relation. The second experiment tested the hypothesis that what can be described as conditional flavor preferences may actually be based on a configural learning process. Participants were exposed to a single-session, eight-trial XA+/A- simultaneous discrimination schedule, the parameters of which were selected so as to enhance the probability of configuring XA, while simultaneously making it likely to observe a pattern of evaluations similar to an X-modulated dislike for A (X was less salient than A). Even though there was good evidence that participants noticed flavor X, they again failed to solve the XA+/A- discrimination and most probably acquired an association between the more salient flavor A and the US. The possibility is discussed that evaluative learning, unlike expectancy learning, might ultimately prove not to be subject to modulation.
authors.affiliation: University of Leuven, Leuven, Belgium.
authors.forename: F
authors.initials: F
authors.lastname: Baeyens
authors.forename: H
authors.initials: H
authors.lastname: Hendrickx
authors.forename: G
authors.initials: G
authors.lastname: Crombez
authors.forename: D
authors.initials: D
authors.lastname: Hermans
mesh_terms: D000328:Adult; D002755:Choice Behavior / Q000502:physiology; D003216:Conditioning, Operant / Q000502:physiology*; D005260:Female; D005421:Flavoring Agents; D006801:Humans; D008297:Male; D013649:Taste / Q000502:physiology*
chemical_list: D005421:Flavoring Agents