Role of stimulus ambiguity in conditional learning.

Abstract

Three experiments using rats and the conditioned emotional response procedure examined the notion that when a conditioned stimulus (CS) is paired with a reinforcer (US), that CS must be ambiguous if the CS-US association is to become the target of conditional control. CS ambiguity was manipulated by varying whether the CS had been preexposed prior to conditioning. In Experiments 1 and 2, it was demonstrated that a cue that accompanied pairings of a CS and shock acquired conditional control over the CS-shock association when that CS had been preexposed, but not when it was novel. The measure of conditional control in Experiments 1 and 2 was the ability of the (conditional) cue to enhance responding to the target CS. Experiment 3 used a blocking procedure to show that this enhancement reflected an amplification of the target CS's effective associative strength. These findings extend existing knowledge of the conditions required for conditional cue formation.

Neither Extended Sequential nor Simultaneous Feature Positive Training Result in Modulation of Evaluative Flavor–Flavor Conditioning in Humans

“…Thus, when after a series of A+acquisition trials, A is next presented unreinforced (A−), these A− trials do not have any influence on the acquired valence of A. If A− trials are likewise causally ineffective when they are presented during FP training (XA+/A−), this may result in the target A lacking a property that might be necessary for occasion setting to occur: an inhibitory component (Rescorla, 1988), or, from a different but related point of view, ambiguity (Bouton, 1993(Bouton, , 1994de Brugada et al, 1995). In order to create such ambiguity which may be resolved by the feature acquiring modulatory properties, a modified FP schedule was used, in which flavor A was reinforced by the negatively valenced Tween20 when presented with feature X, while A was reinforced with the positively valenced sugar when presented without X.…”

Can existing associative principles explain occasion setting? Some old ideas and some new data

“…However this account assumes that occasion setting is impossible if the occasion-set CS has no inhibitory strength, and there is evidence against this position (e.g. de Brugada et al, 1995; trials. In fact numerically the opposite was observed 4 (Figure 2).…”

Negative priming and occasion setting in an appetitive Pavlovian procedure

“…In the present series of experiments, we have argued that if animals respond more to a target stimulus (X) in the presence of the modulator with which it was trained (A) than to the same target stimulus in the presence of another modulator with the same associative strength as A, then this is evidence that A is modulating X, because responding to X in the presence of A is not to be explained in terms of simple Pavlovian conditioning. Although this test has been used quite widely (see, e.g., de Brugada, García-Hoz, Bonardi, & Hall, 1995;Hall & Honey, 1989, 1990, it (along with most others) has been subject to a number of criticisms. First, it relies on the assumption that occasion setting is CS specific-that an occasion setter will be more effective at elevating responding to a target with which it has been trained than to another target stimulus (one would expect some transfer to different CS/modulator combinations even if modulators were CS specific, given that there is likely to be some degree of generalization between the different target CSs).…”