Observing responses maintained by conditional discriminative stimuli.

In a conditional discrimination procedure, pigeons' observing responses were analyzed to examine whether two color stimuli (blue or red), conditionally related to whether each of two line stimuli (vertical or horizontal) accompanied reinforcement or nonreinforcement, functioned as conditioned reinforcers. If a variable-interval (VI) 10-s requirement was fulfilled, an observing response produced onset of a color stimulus. A little later, a line stimulus was presented independently of responding, added to the color stimulus to form a compound stimulus. If 55 s elapsed with a response not having occurred either through 55 s or after the variable-interval 10-s had timed out, one of the color-line compound stimuli was presented independently of responding. To control for sensory reinforcement effects and for earlier entrance to the later link, a simple discrimination procedure also was conducted in which reinforcement was not correlated with the color stimuli but with the line stimuli only. As in the conditional discrimination, the observing response also could produce earlier presentation of blue or red. The observing response occurred more frequently during the conditional discrimination than during the simple discrimination. The results were related to different theoretical accounts of conditioned reinforcement, particularly the information hypothesis.     

Learned suppression of ingestion: role of discriminative stimuli, ingestive responses, and aversive tastes

Three experiments were designed to demonstrate that animals learn to suppress contact with aversive-tasting foods and fluids, and to investigate the behavioral mechanisms of this learning. In Experiment 1, domestic chicks (Gallus gallus) rapidly learned to suppress drinking during a visual stimulus (SQ) that signaled ingestion of a quinine solution but drank normally during a second visual stimulus (SW) that signaled water access. In Experiment 2, chicks in Group Con received oral infusions of quinine contingent upon drinking during SQ. Group Non received oral quinine infusions during SQ yoked to those of Group Con and noncontingent upon drinking. Only Group Con suppressed drinking during SQ. The third experiment investigated the contribution of the aversive taste and the postingestive effects into either the beak or the crop following drinking during SQ. Only the orally infused subjects suppressed drinking during SQ. These studies suggest that the relation between the drinking response and the aversive taste of quinine during SQ is crucial to the learned suppression of ingestion produced by the present procedures. The implications of these results for theories of food selection and Batesian mimicry are discussed.     

On the discriminative control of concurrent responses: the relations among response frequency, latency, and topography in auditory generalization

Human subjects were used in a study of auditory generalization following multiple-response discrimination training. The relations observed among stimulus intensity, response probability, and response latency were invariant with respect to whether the two vocal responses conditioned were topographically discrete, as in one experiment, or topographically continuous, as in another. The major findings were:

1. The probabilities associated with a specific response were maximal over several stimulus values at the extreme ends of the continuum, then dropped sharply at stimuli intermediate to the initial S^D's as the probability of the alternative response increased.

2. Overall response latency was inversely related to the relative frequency of the two responses at each stimulus value. When the two responses were most nearly equal in probability, latencies were maximal; when one response had close to unit or zero probability, latencies were minimal.

3. Analysis of the latencies of the two responses, taken separately, revealed: (a) an increase in latency as the difference between the test stimulus and the initial S^D increased; (b) a sharp discontinuity in the latency gradient and reversal in trend at intermediate stimulus intensities; and (c) at a given stimulus value, latencies associated with the stochastically dominant response were consistently shorter than those of the nondominant response.

4. No changes in response topography (fundamental frequency) were correlated with the characteristic changes in probability and latency during stimulus generalization.

     

Control of responding by the elements of a compound discriminative stimulus and by the elements as individual discriminative stimuli

In the first of two studies, the responding of four albino rats was differentially reinforced in the presence of noise and light together and then tested in the presence of the noise and the light separately during extinction. The light exercised substantially more control of responding than did the noise. In the second study the responding of a similar group of four rats was differentially reinforced in the presence of the noise and the light separately. Control of responding by the light developed more rapidly than control by the noise. Results suggest that levels of control by stimuli after differential reinforcement with respect to the stimuli together can be predicted by the rates of development of control during differential reinforcement with respect to the stimuli separately.     

Instructions as discriminative stimuli

Four undergraduates were exposed to a fixed-ratio schedule under an instruction to respond slowly and to a differential-reinforcement-of-low-rate 5-s schedule under an instruction to respond rapidly. Following this, a fixed-interval schedule was in effect under those same two sets of instructions. For 3 of 4 subjects, response rates were higher with the instruction to respond slowly than with the instruction to respond rapidly during the fixed-interval schedule. For the remaining subject, low-rate responding with the instruction to respond rapidly continued during the first 17 reinforcements of the fixed-interval schedule. Such control by instructions was not observed for other subjects exposed only to a fixed-interval schedule, with or without instructions. The results demonstrate that the effect of instructions can be altered by contingencies and suggest that instructions can function as discriminative stimuli.     

Punishment of observing by the negative discriminative stimulus

To determine the effect of a negative discriminative stimulus on the response producing it, two pigeons were each studied in a three-key conditioning chamber. During alternating periods of unpredictable duration, pecking the center (food) key either was reinforced with grain on a variable-interval schedule or was never reinforced. On equal but independent variable-interval schedules, pecking either of the side (observing) keys changed the color of all keys for 30 sec from yellow to either green or red. When the schedule on the center key was variable-interval reinforcement, the color was green (positive discriminative stimulus); when no reinforcements were scheduled, the color was red (negative discriminative stimulus). Since pecking the side keys did not affect grain deliveries, changes in the rate of pecking could not be ascribed to changes in the frequency of primary reinforcement. In subsequent sessions, red was withheld as one of the possible consequences of pecking a given side key. When red was omitted, the rate on that key increased, and when red was restored, the rate decreased. It was concluded that red illumination of the keys, the negative discriminative stimulus, had a suppressive effect on the response that produced it.     

On science and the discriminative law of effect

This article considers the process of the dissemination of scientific findings from the point of view of the discriminative law of effect. We assume that the purpose of science is to describe the state of the world in an unbiased and accurate manner. We then consider a number of challenges to the unbiased consensual development of science that arise from differences between science that is done, submitted for publication, and published. These challenges arise from the differential reinforcers for both research and publication delivered by journals and editors for novel results, the undervaluation of systematic replication and findings of invariance, and general lack of reinforcers for failed replications. All these challenges bias science toward searching for, reporting, and valuing novel results and consequently lead to a biased and erroneous view of the world. We suggest that science should be approached more conservatively, and that a reevaluation of the value of replication, and especially failed replication, is in order.     

On the emergence of the discriminative mode for transitive-inference

Transitive-inference tasks play increasing roles in many areas of cognitive science. However, discrepancies between the two competing paradigms (classical-Piagetian and IP-paradigm) imply that one paradigm fails to index its target (deductive) competence. Here, potential flaws of one were addressed using considerations from the other. Children of 5–7 years (N=216) solved 3-term transitive problems, some implying a single largest item, and some not. Findings indicate a discriminative competence (a Transitive-Switch) at least 2 years before competence in actually deducing correct solutions. Interestingly, although the transitive-switch was constant across age with both memory and inference increasing with age, it was nevertheless a much stronger predictor of transitive performance than either memory or age. A predictive relationship between memory and inference held for the 5- and 6-year-olds but not the 7-year-olds; suggesting as it approaches maturity, transitive-inference becomes independent of memory. Coincidental with this latter finding, only the 7-year-olds’ transitive performance approximated a deductive competence. As the initial validation of the IP-paradigm rested on acceptance of its age estimate of 4 years, its claim to index deduction must now be revisited.     

Maintenance of behavior controlling the duration of discriminative stimuli

The maintenance of a response controlling the duration of positive and negative discriminative stimuli in a multiple schedule was examined with respect to the possible consequences of the response: none, escape from the negative stimulus, production of the positive stimulus, and initiation of the reinforcement schedule associated with the latter. The last two seemed to be the major factors in producing and maintaining the response. Escape from the negative stimulus maintained it in most subjects, but only at a much lower level.     

Interactions between the discriminative and aversive properties of punishment

Punishment acquires a discriminative property when it is selectively paired with either reinforcement or extinction. At the milder punishment intensities, the discriminative control exerted by punishment is similar to the discriminative control exerted by a response-produced neutral (nonaversive) stimulus. However, the effect of the aversive property is apparent as the intensity of the punishment is increased. The aversive property of the punishment acts to enhance the discriminative control when the punishment is selectively applied during extinction periods, and to attenuate the discriminative control when the punishment is selectively applied during reinforcement periods. One major difference was found between the control exerted by the punishment and the response-produced neutral simulus: Responding greatly increased after the S^Δ punishment but not after the S^Δ neutral stimulus; this increase in responding was independent of the punishment intensities studied.