The effects of delayed reinforcement on variability and repetition of response sequences

Four experiments examined the effects of delays to reinforcement on key peck sequences of pigeons maintained under multiple schedules of contingencies that produced variable or repetitive behavior. In Experiments 1, 2, and 4, in the repeat component only the sequence right-right-left-left earned food, and in the vary component four-response sequences different from the previous 10 earned food. Experiments 1 and 2 examined the effects of nonresetting and resetting delays to reinforcement, respectively. In Experiment 3, in the repeat component sequences had to be the same as one of the previous three, whereas in the vary component sequences had to be different from each of the previous three for food. Experiment 4 compared postreinforcer delays to prereinforcement delays. With immediate reinforcement sequences occurred at a similar rate in the two components, but were less variable in the repeat component. Delays to reinforcement decreased the rate of sequences similarly in both components, but affected variability differently. Variability increased in the repeat component, but was unaffected in the vary component. These effects occurred regardless of the manner in which the delay to reinforcement was programmed or the contingency used to generate repetitive behavior. Furthermore, the effects were unique to prereinforcement delays.     

Disruption of responding maintained by conditioned reinforcement: alterations in response-conditioned-reinforcer relations

An observing procedure was used to investigate the effects of alterations in response-conditioned-reinforcer relations on observing. Pigeons responded to produce schedule-correlated stimuli paired with the availability of food or extinction. The contingency between observing responses and conditioned reinforcement was altered in three experiments. In Experiment 1, after a contingency was established in baseline between the observing response and conditioned reinforcement, it was removed and the schedule-correlated stimuli were presented independently of responding according to a variable-time schedule. The variable-time schedule was constructed such that the rate of stimulus presentations was yoked from baseline. The removal of the observing contingency reliably reduced rates of observing. In Experiment 2, resetting delays to conditioned reinforcement were imposed between observing responses and the schedule-correlated stimuli they produced. Delay values of 0, 0.5, 1, 5, and 10 s were examined. Rates of observing varied inversely as a function of delay value. In Experiment 3, signaled and unsignaled resetting delays between observing responses and schedule-correlated stimuli were compared. Baseline rates of observing were decreased less by signaled delays than by unsignaled delays. Disruptions in response-conditioned-reinforcer relations produce similar behavioral effects to those found with primary reinforcement.     

The emergence of symmetry in a conditional discrimination task using different responses as propioceptive samples in pigeons

In Experiment 1, 10 pigeons were exposed to a successive symbolic matching-to-sample procedure in which the sample was generated by the pigeons' own behavior. Each trial began with both response keys illuminated white, one being the "correct" key and the other the "incorrect" key. The pigeons had no way of discriminating which key was correct and which incorrect, since these roles were assigned on a random basis with the same probability of 0.5 for each key. A fixed ratio of five responses was required on the correct key. However, each time the pigeon pecked the incorrect key, the correct key response counter reset. Five consecutive pecks on the correct key was the only way to end this component, and switch off both key lights. Two seconds later, these same keys were illuminated again, one green and the other red (comparison stimuli). Now, if the correct white key had been on the left, a peck at one color produced food, and if the correct white key had been on the right, a peck at the other color produced food. When the pigeons had learned this discrimination, they were exposed to several symmetry tests (simultaneous presentations of both keys illuminated the same color-i.e., both red or both green), in order to interchange the sample with the comparison stimuli. In Experiment 2, the importance of requiring discrimination between the samples and between the comparisons was analyzed. In Experiment 3, we compared the results of Experiment 1 with a slightly different experiment, which resulted in discrimination of key position, an exteroceptive stimulus. The results showed that symmetry emerged only when different responses were used as samples.     

Resistance to change of responding maintained by unsignaled delays to reinforcement: a response-bout analysis

Previous experiments have shown that unsignaled delayed reinforcement decreases response rates and resistance to change. However, the effects of different delays to reinforcement on underlying response structure have not been investigated in conjunction with tests of resistance to change. In the present experiment, pigeons responded on a three-component multiple variable-interval schedule for food presented immediately, following brief (0.5 s), or following long (3 s) unsignaled delays of reinforcement. Baseline response rates were lowest in the component with the longest delay; they were about equal with immediate and briefly delayed reinforcers. Resistance to disruption by presession feeding, response-independent food during the intercomponent interval, and extinction was slightly but consistently lower as delays increased. Because log survivor functions of interresponse times (IRTs) deviated from simple modes of bout initiations and within-bout responding, an IRT-cutoff method was used to examine underlying response structure. These analyses suggested that baseline rates of initiating bouts of responding decreased as scheduled delays increased, and within-bout response rates tended to be lower in the component with immediate reinforcers. The number of responses per bout was not reliably affected by reinforcer delay, but tended to be highest with brief delays when total response rates were higher in that component. Consistent with previous findings, resistance to change of overall response rate was highly correlated with resistance to change of bout-initiation rates but not with within-bout responding. These results suggest that unsignaled delays to reinforcement affect resistance to change through changes in the probability of initiating a response bout rather than through changes in the underlying response structure.     

A procedure for generating differential "sample" responding without different exteroceptive stimuli

Sidman (1994, 2000) suggested that responses as well as stimuli can join equivalence classes, a hypothesis difficult to test because differential responding typically requires different stimuli. The present experiments describe a procedure with pigeons that avoids this potential confounding effect. In Experiment 1, spacing two responses 3 s apart (a differential-reinforcement-of-low-rate [DRL] schedule) to a white stimulus on some trials produced food or the comparison stimuli in a matching task, whereas pecking 10 or more times with no temporal restrictions (a fixed-ratio [FR] schedule) produced the same effect on other trials. Completing the alternative (unscheduled) requirement terminated the white stimulus and repeated the trial. Following such errors, pigeons learned to switch to the alternative response pattern on the repeat trials. In addition, the correct response pattern functioned as a conditional cue for comparison choice. In Experiment 2, mixed DRL-FR training was preceded by two-sample/two-alternative matching-to-sample with DRL and FR sample-response requirements. In a subsequent transfer test in which the correct response pattern to white served as the sample, pigeons preferentially chose the comparison previously reinforced following that pattern in the baseline task. This "unsignaled response" procedure may be useful for assessing whether differential responses can be members of acquired equivalence classes.     

Do I get what you get? Learning about the effects of self-performed and observed actions in infancy

The present study investigated whether infants learn the effects of other persons' actions like they do for their own actions, and whether infants transfer observed action-effect relations to their own actions. Nine-, 12-, 15- and 18-month-olds explored an object that allowed two actions, and that produced a certain salient effect after each action. In a self-exploration group, infants explored the object directly, whereas in two observation groups, infants first watched an adult model acting on the object and obtaining a certain effect with each action before exploring the objects by themselves. In one observation group, the infants' actions were followed by the same effects as the model's actions, but in the other group, the action-effect mapping for the infant was reversed to that of the model. The results showed that the observation of the model had an impact on the infants' exploration behavior from 12 months, but not earlier, and that the specific relations between observed actions and effects were acquired by 15 months. Thus, around their first birthday infants learn the effects of other persons' actions by observation, and they transfer the observed action-effect relations to their own actions in the second year of life.     

Mister Bixby,Monsieur Bernard,and Some Other 19th Century Scientist–Philosophers on Knowledge-Based Actions

Summary  Following Mr. Bixby and some other 19th century scientist– philosophers such as Claude Bernard, relevant scientific actions should, as a matter of primary importance, be explained with reference to the competence and not to the intentions of those involved. The background is a reliabilist virtue approach – a widespread tendency in 19th century epistemology and philosophy of science. Bixby’s approach includes a critique of some constructivist arguments and establishes a mutually supportive connection to conceptions of scientific progress.     

Resistance to change of forgetting functions and response rates

This experiment examined the effects of reinforcement probability on resistance to change of remembering and response rate. Pigeons responded on a two-component multiple schedule in which completion of a variable-interval 20-s schedule produced delayed matching-to-sample trials in both components. Each session included four delays (0.1 s, 2 s, 4 s, and 8 s) between sample termination and presentation of comparison stimuli in both components. The two components differed in the probability of reinforcement arranged for correct matches (i.e., rich, p = .9; lean, p = .1). Response rates during the variable-interval portion of the procedure were higher in the rich component during baseline and more resistant to the disruptive effects of intercomponent food and extinction. Forgetting functions were constructed by examining matching accuracy as a function of delay duration. Baseline accuracy was higher in the rich component than in the lean component as measured by differences in the gamma-intercept of the forgetting functions (i.e., initial discrimination), rather than from differences in the slope of the forgetting function (i.e., rate of forgetting). Intercomponent food increased the rate of forgetting relatively more in the lean component than in the rich component, but initial discrimination was not systematically affected. Extinction reduced initial discrimination relatively more in the lean component than in the rich component, but did not systematically affect rate of forgetting. These results are consistent with our previous data suggesting that, as for response rate, accuracy and resistance to change of discriminating are positively related to rate of reinforcement. These data also suggest that the disruptability of remembering depends on the conditions of reinforcement, but the way in which remembering is disrupted depends on the nature of the disruptor.     

Associative symmetry in the pigeon after successive matching-to-sample training

If an organism is explicitly taught an A→B association, then might it also spontaneously learn the symmetrical B→A association? Little evidence attests to such “associative symmetry” in nonhuman animals. We report for the first time a clear case of associative symmetry in the pigeon. Experiment 1 used a successive go/no go matching‐to‐sample procedure, which showed all of the training and testing stimuli in one location and intermixed arbitrary and identity matching trials. We found symmetrical responding that was as robust during testing (B→A) as during training (A→B). In Experiment 2, we trained different pigeons using only arbitrary matching trials before symmetry testing. No symmetrical responding was found. In Experiment 3, we trained other pigeons with only arbitrary matching trials and then tested for symmetry. When these pigeons, too, did not exhibit symmetrical responding, we retrained them with intermixed identity and arbitrary matching trials. Less robust symmetrical responding was obtained here than in Experiment 1. Collectively, these results suggest that identity matching may have to be learned concurrently with arbitrary matching from the outset of training for symmetry to emerge.