NEITHER EXTENDED SEQUENTIAL NOR SIMULTANEOUS FEATURE POSITIVE TRAINING RESULT IN MODULATION OF EVALUATIVE FLAVOR-FLAVOR CONDITIONING IN HUMANS

In previous attempts to induce Pavlovian modulation of human evaluativ e flavor-favor associations, the recurrent finding was that exposure t o a Feature Positive (FP) schedule (XA+/A-), in which flavor A was rei nforced by the aversive flavor Tween20 if and only if it was accompani ed by a feature stimulus XI 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 train ing results in a shift from simple A-US learning to the development of X-modulated A-US associations. Participants were exposed to a 32-tria l, 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, par ticipants again acquired a simple unmodulated target A-US association. Contrary to expectations, the additional training sessions did not re sult 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 kno wledge about the conditional X--> (A-US) relation. The second experime nt tested the hypothesis that what can be described as conditional fla vor preferences may actually be based on a configural learning process . Participants were exposed to a single-session, eight-trial XA+/A- si multaneous discrimination schedule, the parameters of which were selec ted so as to enhance the probability of configuring XA: while simultan eously 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 then 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 possi bility is discussed that evaluative learning, unlike expectancy learni ng, might ultimately prove not to be subject to modulation. (C) 1998 A cademic Press.