Repeated acquisitions and extinctions in classical conditioning of the rabbit nictitating membrane response

The rabbit nictitating membrane (NM) response underwent successive stages of acquisition and extinction training in both delay (Experiment 1) and trace (Experiment 2) classical conditioning. In both cases, successive acquisitions became progressively faster, although the largest, most reliable acceleration occurred between the first and second acquisition. Successive extinctions were similar in rate. The results challenge contextual control theories of extinction but are consistent with attentional and layered-network models. The results are discussed with respect to their implications for the interaction between cerebellar and forebrain pathways for eyeblink conditioning.     

Effects of reinforcement history on response rate and response pattern in periodic reinforcement

Several researchers have suggested that conditioning history may have long-term effects on fixed-interval performances of rats. To test this idea and to identify possible factors involved in temporal control development, groups of rats initially were exposed to different reinforcement schedules: continuous, fixed-time, and random-interval. Afterwards, half of the rats in each group were studied on a fixed-interval 30-s schedule of reinforcement and the other half on a fixed-interval 90-s schedule of reinforcement. No evidence of long-term effects attributable to conditioning history on either response output or response patterning was found; history effects were transitory. Different tendencies in trajectory across sessions were observed for measures of early and late responding within the interreinforcer interval, suggesting that temporal control is the result of two separate processes: one involved in response output and the other in time allocation of responding and not responding.     

Effects of effort on response rate

Pigeons were trained to peck for food reinforcement, and the minimum effective force for a peck was varied. In a single-key situation, the response rate was unaffected up to a certain force value, beyond which increments caused a proportional decrement in response rate. Transient enhancement and suppression effects were observed following a change in the force requirement. A change from a high force requirement to a low force requirement resulted in a temporary enhancement of response rate above the stable performance level, whereas a change from a low to a high requirement produced a temporary suppression of the rate below the stable rate. In a two-key situation, the response rate on a key with a given force remained unaffected by the force requirement on the other key. When the rate of response was plotted against the required force, the resultant function was remarkably similar to that obtained from the single-key experiment. When the rates of reinforcement on the two keys differed, the decrement in response rate produced by an increase in the force requirement was proportionally greater on the key with the lower rate of reinforcement.     

The effect of overtraining and repeated extinctions on speed of extinction in electrical self-stimulation

Fourteen rats with hypothalamic electrodes needed at least 3,000 reinforcements in self-stimulation before extinction scores reached their peak. In a series of up to 36 further extinctions and reconditionings, involving a total of 10,500 reinforcements, extinction scores fell to the extreme low values typical of self-stimulation. The extent of this fall was shown to depend on the number of extinctions administered, but not on the number of reinforcements, indicating that a process of conditioned inhibition may be partially responsible for rapid extinction after self-stimulation.     

Effects of voluntary wheel running on heart rate, body temperature, and locomotor activity in response to acute and repeated stressor exposures in rats

Stress often negatively impacts physical and mental health but it has been suggested that voluntary physical activity may benefit health by reducing some of the effects of stress. The present experiments tested whether voluntary exercise can reduce heart rate, core body temperature and locomotor activity responses to acute (novelty or loud noise) or repeated stress (loud noise). After 6 weeks of running-wheel access, rats exposed to a novel environment had reduced heart rate, core body temperature, and locomotor activity responses compared to rats housed under sedentary conditions. In contrast, none of these measures were different between exercised and sedentary rats following acute 30-min noise exposures, at either 85 or 98 dB. Following 10 weeks of running-wheel access, both groups displayed significant habituation of all these responses to 10 consecutive daily 30-min presentations of 98 dB noise stress. However, the extent of habituation of all three responses was significantly enhanced in exercised compared to sedentary animals on the last exposure to noise. These results suggest that in physically active animals, under some conditions, acute responses to stress exposure may be reduced, and response habituation to repeated stress may be enhanced, which ultimately may reduce the negative and cumulative impact of stress.     

Effects of atropine on the repeated acquisition and performance of response sequences in humans.

The present study assessed a 24-hr time course for the acute effects of intramuscular injections of atropine sulfate (0, 1.5, 3.0, and 6.0 mg/70 kg) in healthy adult humans responding under a two-component multiple schedule of repeated acquisition and performance of response sequences. Subjects resided in an inpatient research ward for the duration of the study. In each component of the multiple schedule, subjects completed a different sequence of 10 responses in a predetermined order using three keys of a numeric keypad. In the acquisition component, the subjects' task was to acquire a new sequence each session. Eight sessions were conducted daily: one immediately before administration of the drug and then 0.5, 1.5, 3.0, 5.0, 7.0, 9.0, and 24.0 hr after administration. In the performance component, the response sequence always remained the same. Overall percentage of errors increased and overall response rates decreased in the acquisition and performance components as an orderly function of drug dose. However, these effects were selective in that behavior in the acquisition component generally was affected at lower doses than in the performance component. When behavior was affected in both the acquisition and performance components, the time courses of effects were similar. Drug effects began at 0.5 or 1.5 hr, reached peak effects between 3.0 and 5.0 hr, and returned to placebo levels between 7.0 and 9.0 hr postdrug in both schedule components. None of the drug doses produced reliable effects the day after drug administration (24-hr postdrug) in either schedule component. The present study provides the first within-subject assessment of the magnitude and duration of the effects of an anticholinergic on repeated acquisition and performance baselines and extends to atropine the selective effects on these two baselines demonstrated previously with other compounds in humans and nonhumans.     

Effects of manipulating an antecedent event on mathematics response rate

The purpose of this investigation was to assess the effects on performance rate of simply writing the answers to mathematics problems versus verbalizing the problems before making a written response. The subject was an 11-yr-old boy whose response accuracy on mathematics problems was very erratic. Three experiments were conducted, each consisting of three phases. In each first phase, the subject was requested to write the answers to sets of mathematics problems. In the second, he was required to verbalize the problem before writing the answer. In the third phase, the subject was told to write the answer again without prior verbalization. The results indicated that the subject's correct answer rate increased and his error rate decreased as a result of his verbalizing the problems before making a written response. Results further revealed that in the final phase of each experiment, the return to the original conditions, his correct answer rate continued to increase.     

Effects of GABA modulators on the repeated acquisition of response sequences in squirrel monkeys

The present study investigated the effects of positive and negative GABA(A) modulators under three different baselines of repeated acquisition in squirrel monkeys in which the monkeys acquired a three-response sequence on three keys under a second-order fixed-ratio (FR) schedule of food reinforcement. In two of these baselines, the second-order FR schedule and the discriminative stimuli for the response sequence were manipulated ("chain-strained" and "tandem-strained"). In the third baseline condition, response-independent tail shock was presented during acquisition of the response sequence. All of these baselines maintained high error levels and produced slow rates of acquisition. Under both the chain-strained and tandem-strained conditions, the positive GABA(A) modulator triazolam (0.0032-0.1 mg/kg) and the negative GABA(A) modulators beta-CCE (ethyl-beta-carboline-3-carboxylate; 0.01-1 mg/kg), beta-CCM (methyl-beta-carboline-3-carboxylate; 0.0032-0.1 mg/kg), and FG-7142 (methyl-beta-carboline-3-carboxamide; 0.18-10 mg/kg) dose-dependently decreased overall response rate compared to administration of saline (control). Under the same two conditions, triazolam and the negative GABA(A) modulators also increased the percentage of errors; however, the effects on accuracy frequently depended on the baseline condition and the particular modulator. In contrast, triazolam only decreased errors and enhanced acquisition in the presence of concurrent response-independent tail shock when compared to saline administration under this condition. The neutral GABA(A) modulator, flumazenil (1 mg/kg), had no effect on rate or accuracy of responding when administered alone, but antagonized the rate-decreasing and error-increasing effects produced by the negative GABA(A) modulators. Together, these data suggest that the effects of both the positive and negative GABAA modulators on acquisition can be similar in squirrel monkeys (i.e., both types of modulator may produce rate-decreasing and error-increasing effects) and that their effects on acquisition depend, in part, on the environmental conditions maintaining acquisition.     

Effects of prompting and reinforcement of one response pattern upon imitation of a different modeled pattern

Twelve preschool children participated in a study of the effects of explicit training on the imitation of modeled behavior. The responses trained involved a marble-dropping pattern that differed from the modeled pattern. Training consisted of physical prompts and verbal praise during a single session. No prompts or praise were used during test periods. After operant levels of the experimental responses were measured, training either preceded or was interposed within a series of exposures to modeled behavior that differed from the trained behavior. Children who were initially exposed to a modeling session immediately imitated, whereas those children who were initially trained immediately performed the appropriate response. Children initially trained on one pattern generally continued to exhibit that pattern even after many modeling sessions. Children who first viewed the modeled response and then were exposed to explicit training of a different response reversed their response pattern from the trained response to the modeled response within a few sessions. The results suggest that under certain conditions explicit training will exert greater control over responding than immediate modeling stimuli.     

Effects of variations in local reinforcement rate on local response rate in variable interval schedules

Rats trained to lever press for sucrose were exposed to variable-interval schedules in which (i) the probability of reinforcement in each unit of time was a constant, (ii) the probability was high in the first ten seconds after reinforcement and low thereafter, (iii) the probability was low for ten seconds and high thereafter, (iv) the probability increased with time since reinforcement, or (v) the probability was initially zero and then increased with time since reinforcement. All schedules generated similar overall reinforcement rates. A peak in local response rate occurred several seconds after reinforcement under those schedules where reinforcement rate at this time was moderate or high ([i], [ii], and [iv]). Later in the inter-reinforcement interval, local response rate was roughly constant under those schedules with a constant local reinforcement rate ([i], [ii], and [iii]), but increased steadily when local reinforcement rate increased with time since reinforcement ([iv] and [v]). Postreinforcement pauses occurred on all schedules, but were much longer when local reinforcement rate was very low in the ten seconds after reinforcement ([iii]). The interresponse time distribution was highly correlated with the distribution of reinforced interresponse times, and the distribution of postreinforcement pauses was highly correlated with the distribution of reinforced postreinforcement pauses on some schedules. However, there was no direct evidence that these correlations resulted from selective reinforcement of classes of interresponse times and pauses.     

Timing of movement phases of a repeated response

How can one determine the nature of timing control that exists among various distinct phases of movement in a repetitive activity? A statistical approach is suggested and is exemplified by reference to data on the timing of two phases of movement, arrival at and departure from the response plate, in repetitive finger tapping. Two contrasting models are presented, and the predictions for the covariation of the various intervals between the two movement phases are compared. Data on finger tapping support the model that assumes the initiation of each phase is centrally determined without reference to the time of occurrence of the immediately preceding phase.     

Time allocation and response rate

Food reinforcement for key pecking by three pigeons was arranged by a variable-interval schedule and a device that assigned each reinforcement to one of 10 component response rates corresponding to 10 classes of equally reinforced interresponse times ranging from 1.0 to 6.0 sec in 0.5-sec classes. The overall number of reinforcements per hour was varied from one to more than 60. Overall response rate was a monotonically increasing, negatively accelerated function of the overall number of reinforcements per hour. This function was decomposed into two time-allocation functions: (1) the time allocated to all of the reinforced component response rates as a function of the total reinforcement rate, and, (2) the time allocated to a particular reinforced component response rate as a function of the reinforcement rate for that component. Asymptotic response rate was predicted by combining the asymptotes of the two separate time-allocation functions: virtually all of the time was spent responding, and the percentage of the time spent responding that was allocated to a particular reinforced component response rate roughly equalled the relative reinforcements per hour for that component.     

Effects of pattern, spatial frequency, number, and rate of stimulus presentation on the accuracy of detection.

Brief trains of pulsed stimuli were used to assess whether magnocellular or parvocellular visual pathways could be differentiated perceptually. Trains of either one to four sine-wave, square-wave, or checkerboard gratings were presented at three temporal and two spatial frequencies to six observers. The task of the observer was to report the perceived number of stimuli (gratings) in a train. The difference between actual number and perceived number of gratings was recorded as an error score. It was found that neither the pattern nor the spatial frequency of the gratings significantly affected perceptual accuracy. On the other hand, the number of gratings in a train and the interstimulus interval between gratings produced significant differences. Perceptual accuracy was greater when lower numbers of gratings in a train were presented with longer interstimulus intervals. The observers typically reported fewer stimuli than were presented. The source of the discrepancy is discussed in terms of a light adaptive process initiated in the retina.