Discrimination learning with and without “errors”

Responses to S− (“errors”) are not a necessary condition for the formation of an operant discrimination of color. Errors do not occur if discrimination training begins early in conditioning and if S+ and S− initially differ with respect to brightness, duration and wavelength. After training starts, S−'s duration and brightness is progressively increased until S+ and S− differ only with respect to wavelength. Errors do occur if training starts after much conditioning in the presence of S+ has occurred or if S+ and S− differ only with respect to wavelength throughout training. Performance following discrimination learning without errors lacks three characteristics that are found following learning with errors. Only those birds that learned the discrimination with errors showed (1) “emotional” responses in the presence of S−, (2) an increase in the rate (or a decrease in the latency) of its response to S+, and (3) occasional bursts of responses to S−.     

Early stimulation and patterned responding in rats

This experiment was designed to determine the extent to which performance differences on learning tasks arising from infantile handling reflect learning or emotionality differences. Handled and nonhandled rats were trained and tested in a controlled operant situation where a response on every other trial yielded reinforcement. A key light was turned on for 10 sec during each trial and was off during the 10-sec intertrial interval. The reinforced (S+) trials alternated in a regular sequence with nonreinforced (S–) trials. The pattern of S+ and S– trials recycled continuously throughout the session of 160 trials. The handled rats emitted more responses during both S+ and S– trials than did the nonhandled rats. However, when they were compared on the percentage of emitted responses that were reinforced, there was no significant differences between the two groups. These results were interpreted to suggest that infantile handling does not directly facilitate associative learning in rats.This research was aided by a grant from the National Research Council of Canada, 67-0247. I thank Linda Easton and Beverly Clark for their help in collecting and analyzing the data.     

The effect of negative stimulus presentations on observing-response rates

Theories of observing differ in predicting whether or not a signal for absence of reinforcement (S−) is capable of reinforcing observing responses. Experiments in which S− was first removed from and then restored to the procedure have yielded mixed results. The present experiments suggest that failure to control for the direct effect of presenting S− may have been responsible. Pigeons and operant procedures were used. Experiment 1 showed that presentations of S−, even when not contingent on observing, can raise the rate of an observing response that was reinforced only by presentations of a signal (S+) that accompanied a schedule of food delivery. Experiment 2 showed that this effect resulted from bursts of responding that followed offsets of S−. Experiment 3 showed that, when the presence of S− was held constant, lower rates occurred when S− was dependent on, rather than independent of, observing. These results support theories that characterize S− as incapable of reinforcing observing responses.     

On conditioned reinforcing effects of negative discriminative stimuli

Observing responses by pigeons were studied during sessions in which a food key and an observing key were available continuously. A variable-interval schedule and extinction alternated randomly on the food key. In one condition, food-key pecking during extinction decreased reinforcement frequency during the next variable-interval component, and in the other condition such pecking did not affect reinforcement frequency. Observing responses either changed both keylight colors from white to green (S+) or to red (S−) depending on the condition on the food key, or the observing responses never produced the S+ but produced the S− when extinction was in effect on the food key. Observing responses that produced only S− were maintained only when food-key pecking during extinction decreased reinforcement frequency in the subsequent variable-interval component. The red light conformed to conventional definitions of a negative discriminative stimulus, rendering results counter to previous findings that production of S− alone does not maintain observing. Rather than offering support for an informational account of conditioned reinforcement, the results are discussed in terms of a molar analysis to account for how stimuli acquire response-maintaining properties.     

A further study of stimulus generalization following three-stimulus discrimination training

A group of pigeons was trained in a Skinner box to peck for VI reinforcement when the key was illuminated by a monochromatic light of 540 or 580 mμ but were non-reinforced for responding to 560 mμ. Two control groups, differing in amount of training, received only the two positive stimuli. At the completion of training all Ss received generalization tests under extinction. Both control groups produced bi-modal generalization gradients with the peaks of responding at the S+ values. The post-discrimination gradient revealed peaks displaced from the S+ values in the direction away from the S−, low responding and increased steepness in the region of S− and a general elevation of the gradient.     

Stimulus generalization along a light flicker rate continuum after discrimination training with several S−'s

Four pigeons were trained with VI reinforcement to peck a key which was briefly illuminated by a flickering light. Generalization gradients were then obtained with nine different rates of flicker, four faster than S+ and four slower. Two birds were then trained to discriminate between S+ and the fastest stimulus (S−). These birds were then trained to discriminate between S+ and the two fastest stimuli, alternated as S−'s. This procedure was continued, adding one new S− at a time, until all four stimuli faster than S+ were S−'s. The remaining two birds were trained on this latter discrimination without intervening training. In a final stage, using the first two birds, the slowest stimulus was added as a fifth S−. Generalization gradients in extinction were obtained from each bird after each stage of training. As more stimuli from one end of the continuum served as S−'s, responding increased in the presence of stimuli from the other end of the continuum, and the gradient tended to become flattened at this end.     

Chunking during serial learning by a pigeon: I. Basic evidence

Chunking by pigeons was demonstrated by comparing performance on different types of lists. Experiment 1 showed that Groups II and IV (who learned lists in which colors and achromatic geometric forms were segregated: A----B----C----D'----E' and A----B----C----D----E', respectively) executed lists more rapidly than did Group I (who learned a homogeneous list of colors: A----B----C----D----E) or Groups II and III (who learned lists consisting of unsegregated colors and forms: A----B'----C----D'----E and A----B----C'----D----E, respectively). Experiment 2 showed that Groups II and IV tolerated interruptions of the list better than did Groups I, III, and V. The accuracy of responding of Groups I, III, and V decreased as a function of the duration of the interruption and the point in the sequence at which it occurred. The performance of Group II was unaffected by interruptions; Group IV was minimally affected. These results indicate that Groups II and IV organized their lists as ordered chunks.     

TWO-TO-ONE versus ONE-TO-ONE STUDENT-TEACHER RATIOS IN THE OPERANT VERBAL TRAINING OF RETARDED CHILDREN1

The operant training of two retarded children simultaneously on a picture-naming task was investigated as an alternative to the more commonly reported one-to-one student-teacher ratio. In Experiment I, two conditions were compared in which the children received primary reinforcement on a fixed-ratio schedule for responding correctly on prompt and probe trials in a standardized picture-naming procedure. During the “Group Condition”, the experimenter alternated from one child to the other after each primary reinforcement, after each incorrect response, after each response omission, and after each 10-sec period in which a child did not “attend” (by making a trial-initiating response) when it was his or her turn to be worked with. During the “Individual Condition”, the experimenter worked with only one child, and presented trials whenever the child made attending responses. Experiment I demonstrated that the Group Condition was more efficient than the Individual Condition in terms of total correct responses and total pictures learned per unit of training time. Incidental learning was also found in that the children learned some of each others' pictures as well as their own, thus indicating a further advantage of the larger student-teacher ratio. In Experiment II, an attempt was made to equate the two conditions, except for the presence of two children in the Group Condition, by ignoring the child in the Individual Condition for brief periods equal to those that occurred in the Group Condition when the experimenter presented training trials to the other child. The results demonstrated that the greater efficiency of the Group Condition was not due to the manner in which training time was allocated to the two members of a group. It also replicated the finding that the children learned some of each others' words in the Group Condition.     

Sequential effects of non-reward in a skinner box

The partial reinforcement extinction effect was examined within subjects in a simultaneous discrimination in a two bar Skinner box. Discrete trials were used, rats being required to press the bar under the illuminated cue light; one bar was correlated with 100% the other with 50% reinforcement. The three groups differed in the probability of a change in the cue light between trials during acquisition. When this probability was low, the 50% bar was preferred in extinction, while when it was higher (0.433 or 0.875) the 100% bar was preferred. These results confirm Capaldi's (1966) hypothesis of the partial reinforcement extinction effect, and support a suggested explanation of some conflicting results on partial reinforcement effects in a Skinner box.     

Discriminative effects of massed extincttion

Prior studies have reported that generalization gradients are not steepened if periods of non-reinforcement in S− follow and are not interspersed with periods of reinforcement in S+. Sharper gradients are produced by this massed-extinction procedure if it is preceded by prior discriminative training on a dimension orthogonal to the S+, S− dimension. The present study, using pigeons, found that generalization gradients along the wavelength dimension were steepened by massed-extinction sessions in 570 nm that had been preceded by: (1) discriminative training in which the S+ was a 550-nm light and the S− was a black vertical line superimposed on the 550-nm light; (2) non-differential reinforcement training with a 550-nm light and a black vertical line superimposed on the 550-nm light; (3) reinforcement training with only the 550-nm light. Massed-extinction sessions were administered until the response rate in the presence of the 570-nm stimulus was one-tenth of the mean response rate in the presence of the 550-nm stimulus during prior reinforcement training. Prior studies have used a time-dependent criterion, rather than a response-rate criterion of extinction, and this difference may be responsible for the differences in the effects of massed extinction on stimulus control.     

Stimulus control of schedule-induced activity in pigeons during multiple schedules

Stimulus control of schedule-induced general activity was demonstrated with pigeons using multiple schedules of response-independent food delivery. In Experiment 1, the introduction of food during a multiple variable-time 30-second variable-time 30-second schedule produced a tenfold increase in activity above the no-food baseline. Each pigeon developed stable differential activity rates during the components (correlated with red and green lights) of a multiple variable-time 30-second extinction schedule. Lengthening the extinction component from 1 to 7 minutes increased the rate differences and produced a reliable pattern of responding during S− (the stimulus correlated with extinction): Activity rate was high immediately following the change from S+ (the stimulus correlated with variable-time 30-second) to S−, then decreased abruptly and remained low throughout the middle of the interval, and subsequently showed a positively accelerated increase until the stimulus changed to S+. In Experiment 2, three pigeons were exposed to a mixed variable-time extinction schedule prior to a multiple variable-time extinction schedule. Auditory rather than visual stimuli were used to determine the generality of Experiment 1 results. The multiple- versus mixed-schedule results indicated that stimulus control of activity occurred for two of the birds, but rate differences between S+ and S− were much less than those demonstrated with visual stimuli. A direct comparison of visual and auditory stimulus control in Experiment 3 supported this conclusion. These parallels between the stimulus control of reinforced responding and that of schedule-induced activity suggest that the stimulus control of induced activity may be a factor in operant stimulus control.     

Differential autoshaping to common and distinctive elements of positive and negative discriminative stimuli

The learning by hungry pigeons of a discrimination between two successively presented compound visual stimuli was investigated using a two-key autoshaping procedure. Common and distinctive stimulus elements were simultaneously presented on separate keys and either followed by food delivery, S+, or not, S−. The subjects acquired both between-trial and within-trial discriminations. On S+ trials, pigeons pecked the distinctive stimulus more than the common stimulus; before responding ceased on S− trials, they pecked the common stimulus more than the distinctive one. Mastery of the within-display discrimination during S+ trials preceded mastery of the between-trials discrimination. These findings extend the Jenkins-Sainsbury analysis of discriminations based upon a single distinguishing feature to discriminations in which common and distinctive elements are associated with both the positive and negative discriminative stimuli. The similarity of these findings to other effects found in autoshaping—approach to signals that forecast reinforcement and withdrawal from signals that forecast nonreinforcement—is also discussed.     

Neuropsychological significance of variations in patterns of academic performance: Verbal and visual-spatial abilities

Forty-five 9- to 14-year-old children with learning disabilities whose WISC Full Scale IQs fell within the range of 86–114 were divided into three groups on the basis of their patterns of reading, spelling, and arithmetic achievement. Group 1 was composed of children who were uniformly deficient in reading, spelling, and arithmetic; children in Group 2 were relatively adept at arithmetic as compared to their performance in reading and spelling; Group 3 was composed of children whose reading and spelling performances were average or above, but whose arithmetic performance was relatively deficient. The performances of these children on 16 dependent measures were compared. The performances of Groups 1 and 2 were superior to that of Group 3 on measures of visual-perceptual and visual-spatial abilities; Group 3 performed at a superior level to that of Groups 1 and 2 on measures of verbal and auditory-perceptual abilities. The results are discussed in terms of the relationships between varying patterns of academic abilities and patterns of brain-related behaviors, and the nature of the neuropsychological abilities that may limit performance on arithmetic calculation tasks.The research reported herein was supported, in part, under Grant #195 of the Ontario Mental Health Foundation. Funds were also supplied by Windsor Western Hospital Centre.     

Stimulus generalization as a function of the delay between training and testing procedures: a reevaluation

Three groups of 12 pigeons each were trained to discriminate between lights of 550 mμ (S^D), correlated with 1-min variable-interval reinforcement and 570 mμ (S^Δ), correlated with extinction. Group A was tested for wavelength generalization in extinction 1 min after meeting the discrimination criterion; Group B was tested 24 hr later; Group C was tested 24 hr later after a 3-min (reinforced) warm-up with the S^D. The post-discrimination gradient of Group B was significantly flatter and showed significantly greater area shift than that of Groups A and C. The gradient of Group C was similar to that of Group A, indicating that the warm-up eliminated the effect of the delay period.     

The effects of a signal for free or for earned reward: Implications for the role of response-reinforcer associations in instrumental performance

Pearce and Hall (1978) investigated the effects of making a brief flash of light contingent upon response in rats lever-pressing for food on a variable-interval (VI) schedule. When this signal occurred in conjunction only with reinforced responses the response rate was lowered with respect to a condition in which an equal number of light flashes occurred uncorrelated with reinforcement. The experiments reported here compared these effects with those produced by signalling “free” food deliveries in a similar way. Experiments I and II compared the effects of presenting correlated and uncorrelated schedules of light and food to rats given no opportunity to lever-press. The different schedules did not produce differences in response rate when the levers were made available. In Experiment III, free food was delivered to rats responding on a VI schedule. Signalling the delivery of earned food pellets produced a low response rate in comparison with a condition in which the free pellets were signalled. It is concluded that signalling food delivery is effective only when the rat must respond to earn the food and it is argued that the signal has its effect by overshadowing a response-reinforcer association.     

On knowing how well one is remembering: The persistence of strategy use during transfer

A potential cause for children's failure to transfer learning strategies was explored in the present study. A self-monitoring process was suggested to be essential for evaluating one's own level of performance and the effectiveness of various mnemonic strategies. Matched on free recall scores in this study's first sort-and-recall phase, first, third, and fifth graders (ages 7, 9, and 11 years, respectively) were assigned to one of three treatment groups or a control group. During Phase II, the treatment groups received instruction in sorting pictures according to semantic similarities in preparation for future recall. In addition, Groups 3 and 4 later received feedback indicating their Phase II improvement in performance. A cause-and-effect relationship between strategy use and enhanced recall was further suggested to Group 4. Among third graders, only those provided with feedback and strategy instruction continued to rely upon the input organization strategy when faced with transfer tasks in Phase III. Both enhanced recall and improved sorting styles were observed for these subjects in Phase III. Some first graders also showed improved sorting styles and improved recall following feedback, while fifth graders showed enhanced recall even without experimenter-provided feedback. Subject's responses to a metamemory interview provided additional support for the hypothesis that the self-monitoring of memory performance is more likely to be part of fifth graders' (than first graders') memory abilities.     

Conditioned leg movement in the cat with massed trials,trace conditioning,and weak US intensity

Six male cats served as subjects in a classical conditioning experiment designed to assess the development of an overt conditioned response with experimental parameters that had been demonstrated to produce conditioning of neuro-electrical activity in immobilized cats. The subjects were physically restrained by means of an adjustable full-body cast during the experimental sessions which consisted of 75 habituation trials (light flash alone) followed by 225 trials with light and shock paired in a trace conditioning manner, and 75 additional extinction trials (light alone). The subjects were divided into two groups, and three different experimental sessions were given to each on three consecutive days. Group I received low US intensity (18 v) conditioning on the first day, high US (45–85 v) conditioning on Day 2 and pseudoconditioning on Day 3. Group II received the same sessions, but in a pseudoconditioning —high US—low US order. The results indicated that a conditioned leg movement was produced when the CS was paired in a trace conditioning fashion with either the high or low intensity shock US. The development of the conditioned leg movement across trials was found to be very similar to that of the conditioned neural activity in a previous study using comparable stimuli and procedures.     

Reaction time task as unconditional stimulus

The present study was conducted to demonstrate classic conditioning in electrodermal (ED) and heart rate (HR) responses by using a nonaversive reaction time (RT) task as unconditional stimulus (US). Three groups of 12 subjects each were studied to test the efficacy of this US procedure by varying the essential components of the RT task-US between groups. Eight seconds differential delay conditioning was applied in each group. Simple geometric features (square, cross) displayed on a TV screen were used as CS+ and CS−. RT task consisted of a nonaversive tone (72 dBA, 1000 or 1200 Hz) and a motor response (pressing a button with the left index finger). Subjects were asked to respond as soon as the tone stimulus was presented. The three groups received different stimulus sequences during the 16-trial acquisition phase only. In one group (Group C1), CS+ was followed by a tone to which subjects were to respond, whereas CS− was not followed by a tone. Similarly, in a second group (Group H), CS+ was followed by a tone, whereas CS− was not; however, subjects of Group H (habituation group) were not required to respond to the tone. In a third group, (Group C2) CS+ was followed by a tone to which subjects were to respond, while CS− was followed by a different tone requiring no response. According to analysis of Group C1 data, differential conditioning was obtained in each response measure. Group H displayed habituation in each response measure obtained. In Group C2, differential conditioning was obtained in the second latency window of ED responses only. In all trials, first-interval anticipatory ED responses and HR responses did occur during acquisition, but were not differentiated with respect to the CS conditions. Although the results of Group C2 need further exploration, differential conditioning of HR and in all latency windows of ED responses was demonstrated by the use of a nonaversive RT task as US.     

The development of communication: Attribute variation leads to contrast failure

Groups of 5-year-olds in two experiments described multidimensional triangles for a listener. The attribute differentiating referent triangles from nonreferent triangles in Experiment I was constant across trials for the simple condition group, while any one of three attributes was distinctive on a given trial for the complex condition group. One-adjective messages by subjects in the simple condition were virtually always informative; in the complex group, such messages were predominantly ambiguous. The boundaries of the variation effect were assessed in Experiment II. In addition to the simple-complex variation of the relevant attributes, the values of the irrelevant attributes either varied across trials in the diverse groups or remained constant in the constant groups. One-adjective messages were informative only in the simple-constant group; in the other groups, such messages were predominantly ambiguous. Thus, young children can base their communications on a comparative analysis of stimulus arrays, but performance deteriorates when there is any variation in relevant or irrelevant attributes. These results were discussed in relation to various theories of the development of meaning and communication: the cognitive overload theory, the broad context theory, and the perceptual saliency theory.