Task difficulty and the reinforcement effects of high- and low-frequency stimuli

Cognition and Emotion, 2017

Whether valence change during evaluative conditioning is mediated by a link between the conditional stimulus (CS) and the unconditional stimulus (US; S-S learning) or between the CS and the unconditional response (S-R learning) is a matter of continued debate. Changing the valence of the US after conditioning, known as US revaluation, can be used to dissociate these accounts. Changes in CS valence after US revaluation provide evidence for S-S learning but if CS valence does not change, evidence for S-R learning is found. Support for S-S learning has been provided by most past revaluation studies, but typically the CS and US have been from the same stimulus category, the task instructions have suggested that judgements of the CS should be based on the US, and USs have been mildly valenced stimuli. These factors may bias the results in favor of S-S learning. We examined whether S-R learning would be evident when CSs and USs were taken from different categories, the task instructions were removed, and more salient USs were used. US revaluation was found to influence explicit US evaluations and explicit and implicit CS evaluations, supporting an S-S learning account and suggesting that past results are stable across procedural changes.

Learning & Behavior, 2010

It has long been acknowledged that discrimination training of the kind AX BX results not only in the stimuli involved acquiring different levels of associative strength, but also in changes in the attention they are paid. Over 50 years ago, Lawrence (1949) proposed that this arrangement results in stimuli that are relevant to the discrimination being paid more attention than are irrelevant stimuli. The discrimination above, where A is relevant because it consistently signals reinforcement (S) and B is relevant because it consistently signals nonreinforcement (S), raises the question of whether attention to the former, to the latter, or to both stimuli will be enhanced by this training. At a theoretical level, the answer to this question would appear to be that attention to both cues will be enhanced. Sutherland and Mackintosh (1971) proposed that if a stimulus successfully predicts the outcome of a trial, attention to that stimulus and all other exemplars from the same dimension will increase. Since both S and S meet this requirement, there should be an increase in attention to both. Mackintosh (1975) proposed that attention will increase to a stimulus that is the best predictor of the trial outcome and will generalize to other, similar stimuli. Although the trial outcome was generally regarded as being the presence, rather than the absence, of reinforcement, Mackintosh (1975, p. 288; see also Le Pelley, 2004) acknowledged that his proposals could equally well apply to stimuli that are the best predictors of nonreinforcement. Although there is a growing body of evidence to suggest that attention will be high to stimuli that consistently signal reinforcement (Pearce & Mackintosh, 2010, provide a recent review), there is less evidence showing that attention to stimuli that consistently signal nonreinforcement will also be high. The purpose of the two experiments reported here, therefore, was to determine whether more attention is paid to a stimulus that is a reliable signal for nonreinforcement than to an irrelevant stimulus. If changes in attention occur during discrimination learning, they should be reflected in new learning when the stimuli are used in a different task. However, it is necessary to show that any apparent differences in the associability of these stimuli (the ease with which they are subsequently learned about) are not simply the result of associations acquired during the original training. This problem has been tackled in two main ways. The first involves training subjects, after an initial discrimination has been acquired, with the same stimuli but a different response requirement. In an early experiment of this kind, Lawrence (1949) trained rats to choose between two arms of a maze, which differed in size, brightness, and texture. Only one of these dimensions was relevant, such that approaching one cue (S) from this dimension was reinforced but approaching the other (S) was nonreinforced. Subjects were then transferred to a new task where turning left in the presence of one of the cues from the original training and right in the presence of the other cue from the same dimension was reinforced. Lawrence found that the new discrimination was acquired more readily when the cues had been relevant, rather than irrelevant, for the first discrimination. Because the acquisition of the responses for the new discrimination was intended to be unaffected by the associations formed during the initial training, it was concluded that the original training resulted in more attention being paid to relevant than to irrelevant stimuli. However, it is not clear from Lawrence's result whether attention was enhanced to both relevant cues (S and S) during the original training or just to S .

Learning and Motivation, 2014

2020

This experiment investigated whether noncontingent appetitive stimuli exposure has effects in a subsequent response acquisition with different efforts. On the first phase, rats were exposed to contingent events to nose poke response, noncontingent events, or no exposition. On the second phase, the bar press response of the animals was continuously reinforced or submitted to a FR3 schedule. The time and number of reinforcers to response acquisition varied among subjects, and none relation was identified between first phase exposition with response acquisition of different efforts on phase 2. The longest time in response acquisition identified in some subjects occurred due to competitive responses on the first phase followed by appetitive stimuli. Possibilities for future studies and possible implications for the applied context are discussed.

Journal of Cognition

Prior research showed that the degree of statistical contingency between the presence of stimuli moderates changes in expectancies about the presence of those stimuli (i.e., expectancy learning) but not changes in the liking of those stimuli (i.e., evaluative conditioning). This dissociation is typically interpreted as evidence for dual process models of associative learning. We tested an alternative account according to which both types of learning rely on a single process propositional learning mechanism but reflect different kinds of propositional beliefs. In line with the idea that changes in liking reflect beliefs about stimulus co-occurrences whereas changes in expectancy reflect beliefs about stimulus contingency, we found that evaluative ratings depended only on instructions about whether a stimulus would co-occur with a positive or negative stimulus whereas expectancy ratings were influenced also by instructions about individual stimulus presentations.

Learning and Motivation, 1992

Evaluative conditioning refers to the observation that the mere contingent presentation of neutral with (dis)liked stimuli changes the valence of the originally neutral stimuli in a (negative) positive direction. Two theoretical accounts of the representational structure built up during evaluative conditioning are contrasted: intrinsic change versus referenrial learning. It is argued that previous findings on evaluative conditioning (for example, resistance to extinction) seem to favor intrinsic change explanations, but do not actually allow any definite conclusions. The postconditioning US-revaluation paradigm was used to obtain a more straightforward result. In Experiment 1, a technique was developed to alter the valence of originally strongly (dis)liked USs (pictures of faces). In Experiment 2, we first presented a contingency between neutral (CS) and (dis)liked pictures of faces (US), and next applied the US revaluation technique. Contrary to expectations based on intrinsic change accounts, we observed that the postconditioning US revaluation did affect the acquired value of the CS; this result was confirmed in a l-month follow up. Hence, we conclude that the acquired evaluative meaning of the CS is referential, ultimately relying on an association between CS and US representations. 8

Journal of Applied Behavior Analysis, 2008

Previous research has suggested that the availability of high‐preference stimuli may override the reinforcing efficacy of concurrently available low‐preference stimuli under relatively low schedule requirements (e.g., fixed‐ratio 1 schedule). It is unknown if similar effects would be obtained under higher schedule requirements. Thus, the current study compared high‐preference and low‐preference reinforcers under progressively increasing schedule requirements. Results for 3 of the 4 participants indicated that high‐preference stimuli maintained responding under higher schedule requirements relative to low‐preference stimuli. For 1 participant, high‐preference and low‐preference stimuli were demonstrated to be equally effective reinforcers under increasing schedule requirements. Implications with respect to rate of performance and response patterns are discussed.

Neurobiology of Learning and Memory, 2009

We argue that sensitization and habituation occur to the sensory properties of reinforcers when those reinforcers are presented repeatedly or for a prolonged time. Sensitization increases, and habituation decreases, the ability of a reinforcer to control behavior. Supporting this argument, the rate of operant responding changes systematically within experimental sessions even when the programmed rate of reinforcement is held constant across the session. These within-session changes in operant responding are produced by repeated delivery of the reinforcer, and their empirical characteristics correspond to the characteristics of behavior undergoing sensitization and habituation. Two characteristics of habituation (dishabituation, stimulus specificity) are particularly useful in separating habituation from alternative explanations. Arguing that habituation occurs to reinforcers expands the domain of habituation. The argument implies that habituation occurs to biologically important, not just to neutral, stimuli. The argument also implies that habituation may be observed in ''voluntary" (operant), not just in reflexive, behavior. Expanding the domain of habituation has important implications for understanding operant and classical conditioning. Habituation may also contribute to the regulation of motivated behaviors. Habituation provides a more accurate and a less cumbersome explanation for motivated behaviors than homeostasis. Habituation also has some surprising, and easily testable, implications for the control of motivated behaviors.

Journal of Personality and Social Psychology, 1972

Journal of the Experimental Analysis of Behavior, 1988

After training under short or long fixed-interval schedules, humans responded under a modified fixedinterval schedule in which magnitude of reinforcement (X or 2X) was minimally correlated with response frequency. Response frequencies that equaled or exceeded a minimum response criterion were followed by the larger reinforcer at the end of the interval; otherwise, the smaller reinforcer was delivered. The modified schedule alternated with the baseline schedule across conditions. In a control condition, the reinforcer magnitudes produced by control subjects were yoked to those of experimental subjects. Experimental subjects, but not control subjects, showed increased responding. In addition to the baseline and modified fixed-interval schedules used in Experiment 1, subjects in Experiment 2 also responded under a second modified fixed-interval contingency in which increases in reinforcer magnitude were more highly correlated with response frequency. Experimental subjects, but not control subjects, showed increased responding under both procedures. Direct comparison of these two procedures showed that the high-correlation procedure produced greater increases in responding than did the low-correlation procedure.