A relational differential outcomes effect: pigeons can classify outcomes as “good” and “better”

In a conditional discrimination each of two sample stimuli indicates which of two comparison stimuli is correct. When correct choice following each conditional stimulus is followed by a different outcome (one kind of food following one, a different kind of food following the other) it often facilitates acquisition and improves memory. In transfer designs, in which two different conditional discriminations are followed by the same two differential outcomes, outcome expectation can be shown to be sufficient for comparison choice. That is, the samples from one conditional discrimination are matched to comparisons from the other conditional discrimination based on the common outcomes alone. In the present study we asked if for pigeons the relative value of the differential outcomes (higher versus lower value) can serve as the basis for comparison choice, independent of other characteristics of the outcomes and of differential sample responding. That is, would different outcomes that could be described as “good” and “better” form two stimulus classes. For one conditional discrimination, the differential outcomes involved differential probability of reinforcement for choice of the correct comparison stimulus (0.80 vs. 0.20 for correct choice of the two comparisons, respectively). For the other conditional discrimination, the differential outcomes involved differential responding to the two comparison stimuli (5 pecks vs. 20 pecks to the correct comparisons, respectively). On test trials, when conditional stimuli from the two conditional discriminations were interchanged and the relative value of the differential outcomes could serve as the only basis for comparison choice, we found positive transfer. The results indicate that relational attributes of outcomes can serve as effective cues for comparison choice.     

Imitative learning in Japanese quail (Coturnix japonica) depends on the motivational state of the observer quail at the time of observation

The 2-action method was used to examine whether imitative learning in Japanese quail (Coturnix japonica) depends on the motivational state of the observer quail at the time of observation of the demonstrated behavior. Two groups of observers were fed before observation (satiated groups), whereas 2 other groups of observers were deprived of food before observation (hungry groups). Quail were tested either immediately following observation or after a 30-min delay. Results indicated that quail in the hungry groups imitated, whereas those in the satiated groups did not, regardless of whether their test was immediate or delayed. The results suggest that observer quail may not learn (through observation) behavior that leads to a reinforcer for which they are unmotivated at the time of test. In addition, the results show that quail are able to delay the performance of a response acquired through observation (i.e., they show deferred imitation).     

A cognitive behaviorist approach to the study of animal behavior

Traditional psychological approaches to animal learning and behavior have involved either the atheoretical behaviorist approach proposed by B. F. Skinner (1938), in which input-output relations are described in response to environmental manipulations, or the theoretical behaviorist approach offered by C. L Hull (1943), in which associations mediated by several hypothetical constructs and intervening variables are formed between stimuli and responses. Recently, the application of a cognitive behaviorist approach to animal learning and behavior has been found to have considerable value as a research tool. This perspective has grown out of E. C. Tolman's cognitive approach to learning in which behavior is mediated by mechanisms that are not directly observable but can be inferred from the results of critical experiments. In the present article, the author presents several examples of the successful application of the cognitive behaviorist approach. In each case, the experiments have been designed to distinguish between more traditional mechanisms and those mediated by hypothesized internal representations. These examples were selected because the evidence suggests that some form of active cognitive organization is needed to account for the behavioral results.     

Development of a single-code/default coding strategy in pigeons

We tested the hypothesis that pigeons could use a cognitively efficient coding strategy by training them on a conditional discrimination (delayed symbolic matching) in which one alternative was correct following the presentation of one sample (one-to-one), whereas the other alternative was correct following the presentation of any one of four other samples (many-to-one). When retention intervals of different durations were inserted between the offset of the sample and the onset of the choice stimuli, divergent retention functions were found. With increasing retention interval, matching accuracy on trials involving any of the many-to-one samples was increasingly better than matching accuracy on trials involving the one-to-one sample. Furthermore, following this test, pigeons treated a novel sample as if it had been one of the many-to-one samples. The data suggest that rather than learning each of the five sample-comparison associations independently, the pigeons developed a cognitively efficient single-code/default coding strategy.     

“work ethic” in pigeons: Reward value is directly related to the effort or time required to obtain the reward

Stimuli associated with less effort or with shorter delays to reinforcement are generally preferred over those associated with greater effort or longer delays to reinforcement. However, the opposite appears to be true of stimuli thatfollow greater effort or longer delays. In training, a simple simultaneous discrimination followed a single peck to an initial stimulus (S+_FR1 S−_FR1) and a different simple simultaneous discrimination followed 20 pecks to the initial stimulus (S+_FR20 S−_FR20). On test trials, pigeons preferred S+_FR20 over S+_FR1 and S−_FR20 over S−_FR1. These data support the view that the state of the animal immediately prior to presentation of the discrimination affects the value of the reinforcement that follows it. This contrast effect is analogous to effects that when they occur in humans have been attributed to more complex cognitive and social factors.     

Responding to a positive stimulus by “satiated” pigeons

Skinner (1938) found that rats given discrimination training (Phase I) and then reinforced to “satiation” for responses in the presence of the negative stimulus (S?) (Phase II), began to respond again when the positive stimulus (S+) was reintroduced (Phase III). Experiment I replicated Skinner's finding with pigeons, alternating S+ and S? presentations during Phase III. In Experiment II, Phase II was extended, and Phase III results were similar to those of Experiment I, demonstrating that the recovery of S+ responding could not be attributed to a lax Phase II satiation criterion. In Experiment III, a uniform schedule of reinforcement was maintained throughout the three phases, and results similar to those of Experiment I were found, indicating that renewed S+ responding was not due to the shift in schedule between phases. In Experiment IV, Phase I consisted of discrimination training with two positive stimuli (S+_s and S+_n), and Phase II consisted of reinforcement for responses in the presence of S? and S+_s. During Phase III, significantly more responding was found to S+_s and S+_n than to S?, but no difference in responding was found between the two positive stimuli. In Experiment V, Phase I consisted of simple discrimination training, and during Phase II, responses in the presence of both S? and a novel stimulus (So) were reinforced. During Phase III, significantly more responding was found to S+ than to either S? or So, with no difference found between S? and So responding. Renewed responding to S+ during Phase III in the present experiments is best explained by behavioral contrast developed during Phase I.     

Apprentissage de concepts perceptuels, associationnels et relationnels chez le pigeon

The study of concepts in cognitive psychology has generally been anthropocentric with respect to both content and theory. A broader comparative perspective on the various forms of concept learning would provide a more inclusive view of conceptual behavior. It would also provide a more objective perspective from which to identify underlying processes. Several of the major varieties of conceptual classes claimed for humans alone also appear to be represented in nonhuman animals and young children: perceptual classes involving classification according to the shared attributes of objects, associative classes or functional equivalences in which stimuli form a class based on common associations and relational classes, in which the conceptual relationship between stimuli defines the class.     

PREFERENCE FOR A STIMULUS THAT FOLLOWS A RELATIVELY AVERSIVE EVENT: CONTRAST OR DELAY REDUCTION?

Several types of contrast effects have been identified including incentive contrast, anticipatory contrast, and behavioral contrast. Clement, Feltus, Kaiser, and Zentall (2000) proposed a type of contrast that appears to be different from these others and called it within-trial contrast. In this form of contrast the relative value of a reinforcer depends on the events that occur immediately prior to the reinforcer. Reinforcers that follow relatively aversive events are preferred over those that follow less aversive events. In many cases the delay reduction hypothesis proposed by Fantino (1969) also can account for such effects. The current experiments provide a direct test of the delay reduction and contrast hypotheses by manipulating the schedule of reinforcement while holding trial duration constant. In Experiment 1, preference for fixed-interval (FI) versus differential-reinforcement-of-other-behavior (DRO) schedules of reinforcement was assessed. Some pigeons preferred one schedule over the other while others demonstrated a position (side) preference. Thus, no systematic preference was found. In Experiment 2, a simultaneous color discrimination followed the FI or DRO schedule, and following training, preference was assessed by presenting the two positive stimuli simultaneously. Consistent with the contrast hypothesis, pigeons showed a significant preference for the positive stimulus that in training had followed their less preferred schedule.     

Within-trial contrast: pigeons prefer conditioned reinforcers that follow a relatively more rather than a less aversive event

When behavior suggests that the value of a reinforcer depends inversely on the value of the events that precede or follow it, the behavior has been described as a contrast effect. Three major forms of contrast have been studied: incentive contrast, in which a downward (or upward) shift in the magnitude of reinforcement produces a relatively stronger downward (or upward) shift in the vigor of a response; anticipatory contrast, in which a forthcoming improvement in reinforcement results in a relative reduction in consummatory response; and behavioral contrast, in which a decrease in the probability of reinforcement in one component of a multiple schedule results in an increase in responding in an unchanged component of the schedule. Here we discuss a possible fourth kind of contrast that we call within-trial contrast because within a discrete trial, the relative value of an event has an inverse effect on the relative value of the reinforcer that follows. We show that greater effort, longer delay to reinforcement, or the absence of food all result in an increase in the preference for positive discriminative stimuli that follow (relative to less effort, shorter delay, or the presence of food). We further distinguish this within-trial contrast effect from the effects of delay reduction. A general model of this form of contrast is proposed in which the value of a primary or conditioned reinforcer depends on the change in value from the value of the event that precedes it.