The fate of redundant cues during blocking and a simple discrimination.

Abstract

In each of three experiments animals received blocking, Aϩ AXϩ, in which food was always presented after one stimulus, A, that was occasionally accompanied by another stimulus, X. They also received a simple discrimination, AXϩ BXϪ, in which the presence and absence of food was signaled by two compounds that contained one unique cue, A or B, and one common cue, X. In each of these designs, X can be said to be redundant relative to A as a signal for food. Test trials at the end of training revealed that responding during X was stronger after blocking than after the simple discrimination. These results contradict predictions from theories of learning that assume changes in associative strength of a stimulus are determined by a global error term based on the outcome predicted by all the stimuli that are present for a conditioning trial. The results are interpreted, instead, by assuming either that animals store a memory of every trial to which they have been exposed, or that learning is governed by an error term based on the significance of individual stimuli.Keywords: blocking, relative validity, appetitive conditioning, redundant cuesIn any conditioning task some conditioned stimuli (conditional stimulus, CS) will be more informative about whether the unconditioned stimulus (US) will be delivered than others. Moreover, it appears that informative stimuli gain more control over behavior than those that are uninformative, or redundant. A classic demonstration of this effect was provided by Wagner, Logan, Haberlandt & Price (1968( , see also Wagner, 1969 in an experiment with two groups. One group received what we shall refer to as a simple discrimination in which the US was presented after one compound CS but not another, with each compound containing a unique and a common cue, AXϩ BXϪ. In this discrimination, A can be regarded as informative because it signals reliably whether the US will be delivered, whereas X can be regarded as redundant as it is less informative than A about the delivery of the US. Subsequent test trials revealed a strong conditioned response (CR) in the presence of A, and a weaker CR in the presence of X. The second group received the same two compounds but they were each paired with the US on half of the trials (AXϩ/Ϫ BXϩ/Ϫ). Here, X and A are equally informative about the delivery of the US, and subsequent test trials revealed a stronger CR during X than after the simple discrimination (see also: Pearce, Esber, George & Haselgrove, 2008). Thus even though X was paired with the US according to the same schedule in both groups, it gained less influence over behavior when it was less informative than equally informative about the trial outcome, relative to the stimuli that accompanied it. This outcome of the experiment is referred to as the relative validity effect.Another demonstration of how the informativeness of a stimulus determines the influence it has over behavior is blocking. In the classic demonstration of this effect by Kamin (1969), a blocking group of rats first received trials in...

Uncertainty and blocking in human causal learning.

“…Another phenomenon in which a blocked cue plays an important role is the "redundancy effect", recently described by Pearce and colleagues (Jones & Pearce, 2015;Pearce, Dopson, Haselgrove, & Esber, 2012;Uengoer, Lotz, & Pearce, 2013). In the redundancy effect, a blocked cue (A+/AX+) is compared not to an overshadowing control, but to an uncorrelated cue Y, where training is given with two compounds BY+/CY-.…”

The redundancy effect is related to a lack of conditioned inhibition: Evidence from a task in which excitation and inhibition are symmetrical

“…Following this line of reasoning, other causal learning effects related to inhibition which are discrepant with the predictions of Rescorla-Wagner (1972) model might also be constrained by the properties of the task. One such recently-observed result is the redundancy effect (Uengoer, Lotz, & Pearce, 2013; for analogous results in non-human animals, see Pearce, Dopson, Haselgrove, & Esber, 2012). Uengoer et al trained participants to predict whether or not a fictional patient would suffer a stomach ache when he consumed various different foods.…”

The fate of redundant cues: Further analysis of the redundancy effect

“… Pearce, Dopson, Haselgrove, and Esber ( Journal of Experimental Psychology: Animal Behavior Processes , 38, 167–179, 2012 ) conducted a series of experiments with rats and pigeons in which the conditioned responding elicited by two types of redundant cue was compared. One of these redundant cues was a blocked cue X from A+ AX+ training, whereas the other was cue Y from a simple discrimination BY+ CY–.…”

“…Additionally, recent attempts to test this prediction have produced the opposite result. Pearce, Dopson, Haselgrove, and Esber ( 2012 ) conducted experiments with both rats and pigeons, in which training of the form A+ AX+ BY+ CY– was given. This training contained both types of redundant cue already described.…”