Nondifferential Reinforcement Research Articles

Divided stimulus control depends on differential and nondifferential reinforcement: Testing a quantitative model.

We investigated the effects of differential and nondifferential reinforcers on divided control by compound-stimulus dimensions. Six pigeons responded in a delayed matching-to-sample procedure in which a blue or yellow sample stimulus flashed on/off at a fast or slow rate, and subjects reported its color or alternation frequency. The dimension to report was unsignaled (Phase 1) or signaled (Phase 2). Correct responses were reinforced with a probability of .70, and the probability of reinforcers for errors varied across conditions. Comparison choice depended on reinforcer ratios for correct and incorrect responding; as the frequency of error reinforcers according to a dimension increased, control (measured by log d) by that dimension decreased and control by the other dimension increased. Davison and Nevin's (1999) model described data when the dimension to report was unsignaled, whereas model fits were poorer when it was signaled, perhaps due to carryover between conditions. We are the first to test this quantitative model of divided control with reinforcers for errors and when the dimension to report is signaled; hence, further research is needed to establish the model's generality. We question whether divided stimulus control is dimensional and suggest it may instead reflect joint control by compound stimuli and reinforcer ratios.

Floral guidance of learning a preference for symmetry by bumblebees.

This study examines the mechanism underlying one way in which bumblebees are known to develop a preference for symmetric patterns: through prior non-differential reinforcement on simple patterns (black discs and white discs). In three experiments, bees were given a choice among symmetric and asymmetric black-and-white non-rewarding patterns presented at the ends of corridors in a radial maze. Experimental groups had prior rewarded non-discrimination training on white patterns and black patterns, while control groups had no pre-test experience outside the colony. No preference for symmetry was obtained for any of the control groups. Prior training with circular patterns highlighting a horizontal axis of symmetry led to a specific subsequent preference for horizontal over vertical symmetry, while training with a vertical axis abolished this effect. Circles highlighting both axes created a general avoidance of asymmetry in favour of symmetric patterns with vertical, horizontal or both axes of symmetry. Training with plain circles, but not with deformed circles, led to a preference for symmetry: there was no evidence that the preference emerged just by virtue of having attention drawn away from irrelevant pattern differences. Our results point to a preference for symmetry developing gradually through first learning to extract an axis of symmetry from simple patterns and subsequently recognizing that axis in new patterns. They highlight the importance of continued learning through non-differential reinforcement by skilled foragers. Floral guides can function not only to guide pollinators to the source of reward but also to highlight an axis of symmetry for use in subsequent floral encounters.

Using rich-to-lean transitions following errors during discrete-trial instruction

ABSTRACTResearch on error correction procedures often includes the manipulation of prompting strategies or reinforcement schedules during discrete-trial instruction (DTI). We extended this research by incorporating rich-to-lean reinforcement transitions following incorrect responses with four boys diagnosed with autism spectrum disorder. With the rich-to-lean error correction procedure, less-preferred reinforcers were delivered for the next two to three correct responses following an error. This condition was compared to non-differential reinforcement, in which more-preferred items were delivered for both correct responses or attempts, and a traditional differential reinforcement procedure, in which more-preferred items were delivered for correct responding and no items were delivered following attempts. The rich-to-lean condition resulted in the acquisition of the targeted skills with two of the four participants. The traditional differential reinforcement procedure was effective with three participants (and most efficient for two of those), and the non-differential procedure was effective (and most efficient) for one participant. We suggest that rich-to-lean transitions might function to correct errors in the context of DTI.

An assessment of differential reinforcement procedures for learners with autism spectrum disorder.

Differential reinforcement procedures may promote unprompted correct responding, resulting in a quicker transfer of stimulus control than nondifferential reinforcement. Recent studies that have compared reinforcement arrangements have found that the most effective arrangement may differ across participants. The current study conducted an assessment of differential reinforcement arrangements (i.e., quality, schedule, and magnitude) and nondifferential reinforcement to identify the most effective arrangement for each participant. The assessment phase showed that the quality arrangement was the most efficient for all participants during auditory-visual matching. Next, a validation phase was conducted to evaluate whether the assessment would predict the most effective arrangement across multiple skills. The results from the assessment phase were validated for all participants for the same skill. However, the results were only validated for one participant during the other skills (i.e., tact and intraverbal). The results are discussed in light of previous research and future areas of research.

Concept learning without differential reinforcement in pigeons by means of contextual cueing.

How supervision is arranged can affect the way that humans learn concepts. Yet very little is known about the role that supervision plays in nonhuman concept learning. Prior research in pigeon concept learning has commonly used differential response-reinforcer procedures (involving high-level supervision) to support reliable discrimination and generalization involving from 4 to 16 concurrently presented photographic categories. In the present project, we used contextual cueing, a nondifferential reinforcement procedure (involving low-level supervision), to investigate concept learning in pigeons. We found that pigeons were faster to peck a target stimulus when 8 members from each of 4 categories of black-and-white photographs-dogs, trees, shoes, and keys-correctly cued its location than when they did not. This faster detection of the target also generalized to 4 untrained members from each of the 4 photographic categories. Our results thus pass the prime behavioral tests of conceptualization and suggest that high-level supervision is unnecessary to support concept learning in pigeons.

A comparison of differential reinforcement procedures with children with autism.

The current evaluation compared the effects of 2 differential reinforcement arrangements and a nondifferential reinforcement arrangement on the acquisition of tacts for 3 children with autism. Participants learned in all reinforcement-based conditions, and we discuss areas for future research in light of these findings and potential limitations.

Validating the virtual string task with the gap test.

Relational concepts-such as connectedness-may be easy for human adults to appreciate; but, obtaining evidence of other species' understanding of connectedness has been challenging. One key test of connectedness involves an organism's responding to variants of the string task. Using a virtual string task, we gave pigeons a pair of strings from which to choose: one connected to a full dish of food and a second disconnected from another full dish of food. Our pigeons did not at first choose the connected string under conditions of non-differential reinforcement; later, the birds rapidly learned to choose the connected string under conditions of differential reinforcement. Our results replicate prior findings with real strings and food dishes, thereby demonstrating that pigeons can appreciate the connectedness between a string tether and a dish of food, and attesting to the utility and fidelity of the virtual string task.

A Zoo-housed Chimpanzee’s (Pan troglodytes) Responses to Potentially Arousing Stimuli

In Experiment 1, we wished to determine whether a singly-housed adult male captive chimpanzee could discriminate the behavioral categories of sex and aggression. He was reinforced for selecting sexual rather than aggressive images on a touch-screen computer in a two-choice discrimination paradigm. He showed no discrimination after 24 sessions with non-human photos, but immediately selected human sexual images at above-chance levels. To explore whether this differential discrimination was due to a preference for human sexual images, he was presented with images of humans versus non-humans under non-differential reinforcement in Experiment 2. He preferred human photos if the images depicted sex, but not if the images depicted aggression. To further explore these preferences in Experiment 3 the chimpanzee was presented with images of genitalia of non-humans versus humans, genitalia versus eyes, and finally female versus male genitalia of both non-humans and humans, using non-differential reinforcement. The chimpanzee preferred human to non-human genitalia, and eyes to genitalia, but did not prefer female to male genitalia. This chimpanzee’s unusual social environment may have interfered with species-typical social preferences.

The effects of differential reinforcement of unprompted responding on the skill acquisition of children with autism.

The recommendation to reserve the most potent reinforcers for unprompted responses during acquisition programming has little published empirical support for its purported benefits (e.g., rapid acquisition, decreased errors, and decreased prompt dependence). The purpose of the current investigation was to compare the delivery of high-quality reinforcers exclusively following unprompted responses (differential reinforcement) with the delivery of high-quality reinforcers following both prompted and unprompted responses (nondifferential reinforcement) on the skill acquisition of 2 children with autism. Results indicated that both were effective teaching procedures, although the differential reinforcement procedure was more reliable in producing skill acquisition. These preliminary findings suggest that the differential reinforcement of unprompted responses may be the most appropriate default approach to teaching children with autism.

Spontaneous discrimination of natural stimuli by chimpanzees (Pan troglodytes).

Six chimpanzees (Pan troglodytes) were presented with pairs of color photographic images of 5 different categories of animals (cat, chimp, gorilla, tiger, fish). The subjects responded to each pair using symbols for "same" and "different." Both within- and between-category discriminations were tested, and all chimpanzees classified the image pairs in accordance with the 5 experimenter-defined categories under conditions of nondifferential reinforcement. Although previous studies have demonstrated identification or discrimination of natural categories by nonhuman animals, subjects were typically differentially reinforced for their responses. The present findings demonstrate that chimpanzees can classify natural objects spontaneously and that such classifications may be similar to those that would be observed in human subjects.

The effects of delay interval, intertriai interval, amnestic drugs, and differential outcomes on matching-to-position in rats

A matching-to-position task was used to investigate the effects of numerous variables on spatial working memory in the rat. The primary interest was whether implementing the differential outcomes procedure (DOP), which correlates specific reinforcers with specific discriminative stimuli, would enhance memory performance under a variety of conditions (long delay intervals, short intertrial-intervals [ITIs], amnestic drugs). When working memory was taxed, either by excessive delay intervals or very short ITIs, the DOP did enhance performance. Scopolamine disrupted performance in a delay-dependent manner, regardless of either reinforcement or ITI condition; however, performance was worse in the group that was trained with nondifferential reinforcement. MK-801 also impaired performance, but the effect was different from that obtained with scopolamine. First, the effect of MK-801 was delay independent; second, the greatest disruption of performance was in the group of rats trained with differential reinforcement. These data suggest that scopolamine and MK-801 impair memory performance in very different ways, depending on the nature of the task.

Language-naive chimpanzees (Pan troglodytes) judge relations between relations in a conceptual matching-to-sample task.

Three chimpanzees with a history of conditional and numeric token training spontaneously matched relations between relations under conditions of nondifferential reinforcement. Heretofore, this conceptual ability was demonstrated only in language-trained chimpanzees. The performance levels of the language-naive animals in this study, however, were equivalent to those of a 4th animal--Sarah--whose history included language training and analogical problem solving. There was no evidence that associative factors mediated successful performance in any of the animals. Prior claims of a profound disparity between language-trained and language-naive chimpanzees apparently can be attributed to prior experience with arbitrary tokens consistently associated with abstract relations and not language per se.

What Is the Role of Reinforcement in Early Language Acquisition?

Monolingual American and Mexican 2- and 3-year-old children were exposed to a foreign language in a naturalistic but controlled environment. Children were randomly assigned to 2 groups. 1 group was differentially reinforced throughout the study for the use of foreign vocabulary. The control group was first reinforced nondifferentially for use of the native language or the foreign language and later was switched to differential reinforcement for the foreign language. Frequencies of spontaneous foreign word production and other verbal responses were computed, and formal assessments of comprehension and production of the foreign words were conducted. Differential reinforcement resulted in accelerating frequencies of spontaneous foreign language use and better performance on both comprehension and production tests. Under nondifferential reinforcement, rates of spontaneous foreign language use were low and static. Results are interpreted as evidence that the acquisition of expressive vocabulary is a function of socially mediated reinforcement.

Stacking blocks by chimpanzees

Cognitive development of chimpanzees was directly compared to that of human children in the diagnostic test of “stacking blocks”. Four 4-year-old, one 10-year-old (Ai), and one 27-year-old (Sarah) chimpanzees were served as subjects. The ability of stacking blocks (1 inch cubes) was tested with non-differential reinforcement using social praise in two situations. In the “free stacking” situation, the subjects received a bunch of blocks at once and was asked to use them up to build as many towers as they like. After the subjects received a number of sessions for the “exercise”, they were tested in the “forced stacking” situation, in which the subjects received each block one at a time and was asked to make a high tower. All the chimpanzees constructed the tower of at least 9 blocks. The highest tower made by the chimpanzees had 12 stories. The older two chimpanzees were a little superior to the younger ones on the average. The level of performance matches that of 2-year-old human children. The chimpanzees adjusted the four corners of blocks to make a straight tower and rejected to put one more block “foreseeing” how the tower of blocks turns out. The cognitive aspects found in the stacking behavior were discussed in the framework of the protogrammar of action.

Hyperstriatal lesions and attention in the pigeon.

In two experiments, pigeons with bilateral lesions of the hyperstriatum were compared with unoperated control birds on tasks designed to test an attentional account of hyperstriatal function. In both experiments, hyperstriatal lesions disrupted reversal learning but did not influence the retardation of learning associated with either nonreinforced preexposure to the to-be-conditioned stimulus (Experiment 1) or prior nondifferential reinforcement to the to-be-discriminated stimuli (Experiment 2). There was, however, evidence of an impairment in both the acquisition and maintenance of autoshaped responding in lesioned birds, an impairment which may reflect a disruption of classical associations in hyperstriatal pigeons.

Contiguity and contingency in the acquisition and maintenance of an operant

Three experiments compared the effects of nondifferential and differential reinforcement of response location on a circular dimension. Rats were required to operate a vertical joystick to produce food. When food was delivered immediately after responses, but independent of response location, the spatial concentration of responding was low and no progressive changes were observed. Traditional and percentile schedules of differential reinforcement for response location produced highly reliable acquisition of spatially concentrated responding. Once concentrated responding had been established, nondifferential reinforcement was sufficient to maintain it in some subjects. Since only the differential reinforcement schedules established a contingency with respect to response location, it was concluded that this relationship was necessary for acquisition, but that response-reinforcer contiguity may be sufficient for maintenance. This conclusion is consistent with the view that operant conditioning is a contiguity-based process, but that contingencies are required to produce reliable contiguity between reinforcers and particular responses.

Effect of N-R transitions during partial reinforcement pretraining on subsequent resistance to discrimination

Three groups of 12 rats received 25 pretraining trials to each future discriminandum employed in a subsequent differential brightness conditioning problem. Groups NR and RN received partial reinforcement (PRF) pretraining either with or without, respectively, transitions from nonrewarded to rewarded trials (N-R transitions). Group CRF received consistent reinforcement during pretraining. A fourth group (n=12), Group NP, received no pretraining. During discrimination learning, one-half of the rats in each group received all their daily S+ trials preceding their daily S− trials (+− sequence); the remainder of the rats received an intermixed sequence of trials to S+ and S− (+−+ sequence). Discrimination learning was faster under the +− sequence than under the +−+ condition, and discrimination learning was retarded in Group NR relative to the other three groups, which did not differ from one another, under both the +− and +−+ discrimination sequence conditions. The results are discussed with Reference to previous experiments demonstrating N-R transition effects on discrimination learning, a theoretical extension of sequential theory to discrimination learning, and the effects of nondifferential reinforcement prior to discrimination learning on learned irrelevance.

Blocking in successive differential conditioning: Prior acquisition of control by internal cues blocks the acquisition of control by brightness

In each of four experiments the acquisition of discriminative stimulus control by brightness cues (black vs white runway) in a successive go/no-go instrumental discrimination was blocked in groups given prior discrimination training with internal (reward-produced and intertrial interval-related) cues as relevant discriminanda and brightness cues irrelevant. The blocking effects obtained here in instrumental conditioning were substantial and in most cases complete. Blocking occurred whether brightness in Phase I varied across trials but was uncorrelated with reinforcement (varied-irrelevant, V-I, condition) or whether all Phase 1 trials occurred to a single value on the brightness dimension (constant-irrelevant, C-I, condition) which then served as a redundant S+ cue in Phase 2 while the previously unexperienced brightness cue was added to the S- stimulus compound, or vice versa. Blocking in the V-I condition was shown not to be due simply to nondifferential reinforcement of brightness in Phase 1, but to depend on the prior acquisition of discriminative stimulus control by internal cues. As in Pavlovian conditioning, blocking here was an increasing function of amount of prior conditioning to the blocking stimulus. The results encourage the prospect that the procedures used here can be developed into a viable instrumental conditioning companion to the Pavlovian procedures now used almost exclusively to study blocking.

DIFFERENTIAL RESPONDING WITHOUT DIFFERENTIAL REINFORCEMENT: INTENSITY DIFFERENCE, CONTINUUM POSITION, AND REINFORCEMENT DENSITY EFFECTS

The response rates of five groups of rats were observed during exposure to different intensities of a four kilohertz tone within a two-component multiple schedule of nondifferential reinforcement. Response rates were found to be higher during the multiple schedule component which contained the higher intensity tone. Larger differences in response rates between the two multiple schedule components occurred with greater intensity separations (30 versus 20 decibels). At the 30 decibel separation a low absolute magnitude produced larger response rate differences than a high absolute magnitude, while at the 20 decibel separation a high absolute magnitude produced larger response rate differences. Increases in reinforcement density were accompanied by decreases in response rate differences between high and low intensity components only when over-all response rates also increased.

A search for perceptual differentiation produced by nondifferential reinforcement.

In each of four experiments (three using pigeons as the subjects and one using rats) animals in an experimental condition were given exposure to a pair of stimuli that subsequently they were required to discriminate between. During the exposure phase response to either stimulus was consistently followed by reward. These subjects were uniformly found to be retarded in learning the discrimination when compared with control subjects that received equivalent pre-training in the absence of the critical stimuli. These results provide no support for the suggestion that stimuli may become “perceptually differentiated” during the pre-training phase but are consistent with the proposal that novel stimuli possess a high level of associability that declines as a result of experience.