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1.
Pigeons could choose between five concurrently available response keys, each associated with a different variable-interval schedule of reinforcement. A 2-sec changeover delay was also in effect on each key. In almost all cases, the relative number of responses to a key and the relative time spent at it were nearly equivalent to the relative number of reinforcements it produced. In addition, matching was observed between the relative number of reinforcements at a key and the relative number of changeovers to it. 相似文献
2.
James E. Mazur 《Learning & behavior》1995,23(1):93-103
Pigeons pecked on two response keys that delivered reinforcers on a variable-interval schedule. The proportion of reinforcers delivered by one key was constant for a few sessions and then changed, and subjects’ choice responses were recorded during these periods of transition. In Experiment 1, response proportions approached a new asymptote slightly more slowly when the switch in reinforcement proportions was more extreme. In Experiment 2, slightly faster transitions were found with higher overall rates of reinforcement. The results from the first session, after a switch in the reinforcement proportions, were generally consistent with a mathematical model that assumes that the strength of each response is increased by reinforcement and decreased by nonreinforcement. However, neither this model nor other similar models predicted the “spontaneous recovery” observed in later sessions: At the start of these sessions, response proportions reverted toward their preswitch levels. Computer simulations could mimic the spontaneous recovery by assuming that subjects store separate representations of response strength for each session, which are averaged at the start of each new session. 相似文献
3.
Twenty acquisition curves were obtained from each of 8 pigeons in a free-operant choice procedure. Every condition began with a phase in which two response keys had equal probabilities of reinforcement, and, as a result, subjects’ responses were divided fairly evenly between the two keys. This was followed by a phase in which one key had a higher probability of reinforcement than the other, and the development of preference was observed. In all but a few cases, response proportions increased for the key with the higher probability of reinforcement. In most conditions, the two probabilities differed by .06, but the actual probabilities varied (from .16 and .10 in one condition to .07 and .01 in another). Development of preference for the key with the higher probability of reinforcement was slower when the ratio of the two reinforcement probabilities was small (.16/.10) than when it was large (.07/.01). This finding is inconsistent with the predictions of several different quantitative models of acquisition, including the kinetic model (Myerson & Miezin, 1980) and the ratio-invariance model (Horner & Staddon, 1987). However, the finding is consistent with a hypothesis based on Weber’s law, which states that the two alternatives are more discriminable when the ratio of their reinforcement probabilities is larger, and, as a result, the acquisition of preference is faster. 相似文献
4.
We trained 4 pigeons in a numerical bisection task to discriminate between pairs of keylight flashes with a ratio of 1∶3 (2
vs. 6, 4 vs. 12, and 8 vs. 24) that were presented in a sample phase. Responses to the blue key were reinforced after a sequence
of a larger number of flashes, and responses to the white key were reinforced after a sequence of a smaller number of flashes.
The intervals between flashes in the sample phase were randomized to attenuate the covariation of temporal cues with flash
number. Pigeons responded accurately in each of the discriminations, with typically 85%–90% correct responses. Transfer tests
showed that the proportion of large responses increased with number and performance generalized to larger values outside the training ranges. Psychometric functions
superposed when plotted on a relative scale, and estimates of Weber fractions were approximately constant, suggesting that
variability was scalar. However, contrary to previous research in nonhumans, bisection points were located at the arithmetic,
not geometric, mean. Hierarchical logistic regressions confirmed significant control over responding by number beyond that
attributable to temporal cues. These results show that pigeons are able to respond accurately in a relative numerosity discrimination
with successively presented visual stimuli, although the nature of the numerical representation and response rule remains
unclear. 相似文献
5.
Pigeons searched for two targets that varied in similarity to items in the background. The targets, simulating “prey,” were small alphabetic characters presented on computer monitors among distractor characters. In the first experiment, the probability of reinforcement for pecking at the targets was manipulated. In the second experiment, the response requirement for one of the targets was varied. Changing the probability of reinforcement led to more efficient search and increased choice for the more reinforced item. This effect carried over to subsequent equal reinforcement baseline conditions. Increasing the response requirement for one item increased response time for that item and reduced choice of the item. This effect did not carry over to a subsequent baseline condition. The results suggested that a high probability of reinforcement resulted in improved detection of the item, perhaps through perceptual learning, and increased the incentive that motivated response to the item, but that high response requirement resulted only in an incentive shift. 相似文献
6.
James E. Mazur 《Learning & behavior》1996,24(1):1-10
Pigeons’ responses on two keys were recorded before and after the percentage of reinforcers delivered by each key was changed. In each condition of Experiment 1, the reinforcement percentage for one key was 50% for several sessions, then either 70% or 90% for one, two, or three sessions, and then 50% for another few sessions. At the start of the second and third sessions after a change in reinforcement percentages, choice percentages often exhibited spontaneous recovery—a reversion to the response percentages of earlier sessions. The spontaneous recovery consisted of a shift toward a more extreme response percentage in some cases and toward a less extreme response percentage in other cases, depending on what reinforcement percentages were previously in effect. In Experiment 2, some conditions included a 3-day rest period before a change in reinforcement percentages, and other conditions included no such rest days. Slightly less spontaneous recovery was observed in conditions with the rest periods, suggesting that the influence of prior sessions diminished with the passage of time. The results are consistent with the view that choice behavior at the start of a new session is based on a weighted average of the events of the past several sessions. 相似文献
7.
Frances K. McSweeney 《Learning & behavior》1978,6(4):444-450
Four pigeons pecked keys and pressed treadles for food reinforcers delivered by several variable-interval schedules of reinforcement. Then the subjects responded on several concurrent schedules. Keypecking produced reinforcers in one component, and treadle-pressing produced reinforcers in the other. The changeover delay, which prevented reinforcement after all switches from one response to the other, was 0, 5, or 20 sec long. An equation proposed by Kerrnstein (1970) described the rates of treadle-pressing and keypecking emitted during the variable-interval schedules. The k parameter of this equation was larger for keypecking than for treadle-pressing. The R0 parameters were not systematically different for the two responses. The rates of keypecking and treadle-pressing emitted during the components of the concurrent schedules correlated with, but were not equal to, the rates of responding predicted by Herrnstein’s equation and the subject’s simple schedule responding. The ratios of the rates of responding emitted during, and the ratios of the time spent responding on, the components of the concurrent schedules conformed to an equation proposed by Baum (1974), but not to Herrnstein’s equation. 相似文献
8.
In Experiment 1, three food-deprived pigeons received trials that began with red or green illumination of the center pecking key. Two or four pecks on this sample key turned it off and initiated a 0- to 10-sec delay. Following the delay, the two outer comparison keys were illuminated, one with red and one with green light. In one condition, a single peck on either of these keys turned the other key off and produced either grain reinforcement (if the comparison that was pecked matched the preceding sample) or the intertrial interval (if it did not match). In other conditions, 3 or 15 additional pecks were required to produce reinforcement or the intertrial interval. The frequency of pecking the matching comparison stimulus (matching accuracy) decreased as the delay increased, increased as the sample ratio was increased, and decreased as the comparison ratio was increased. The results of Experiment 2 suggested that higher comparison ratios adversely affect matching accuracy primarily by delaying reinforcement for choosing the correct comparison. The results of Experiment 3, in which delay of reinforcement for choosing the matching comparison was manipulated, confirmed that delayed reinforcement decreases matching accuracy. 相似文献
9.
Pigeons pecked keys on concurrent-chains schedules that provided a variable interval 30-sec schedule in the initial link.
One terminal link provided reinforcers in a fixed manner; the other provided reinforcers in a variable manner with the same
arithmetic mean as the fixed alternative. In Experiment 1, the terminal links provided fixed and variable interval schedules.
In Experiment 2, the terminal links provided reinforcers after a fixed or a variable delay following the response that produced
them. In Experiment 3, the terminal links provided reinforcers that were fixed or variable in size. Rate of reinforcement
was varied by changing the scheduled interreinforcer interval in the terminal link from 5 to 225 sec. The subjects usually
preferred the variable option in Experiments 1 and 2 but differed in preference in Experiment 3. The preference for variability
was usually stronger for lower (longer terminal links) than for higher (shorter terminal links) rates of reinforcement. Preference
did not change systematically with time in the session. Some aspects of these results are inconsistent with explanations for
the preference for variability in terms of scaling factors, scalar expectancy theory, risk-sensitive models of optimal foraging
theory, and habituation to the reinforcer. Initial-link response rates also changed within sessions when the schedules provided
high, but not low, rates of reinforcement. Within-session changes in responding were similar for the two initial links. These
similarities imply that habituation to the reinforcer is represented differently in theories of choice than are other variables
related to reinforcement. 相似文献
10.
Pigeons were studied on multiple variable-ratio yoked-variable-interval schedules in which components had equal rates of food reinforcement and appeared equally often on each of two keys. Interpolated between component changes on the final multiple schedule were 10-sec probes in which both schedule stimuli were present, one on each key. During multiple schedule training, variable-ratio response rates were greater than yoked-variable-interval rates; however, response rate differences in the components were not a function of the mean ratio value for the 40-to-320-ratio range studied. During the choice probes, subjects responded more to the stimulus associated with the interval schedule than to the one associated with the ratio schedule. It was concluded that pigeons prefer interval schedules over equal reinforcement rate ratio schedules, because the former generate fewer responses per reinforcement. 相似文献
11.
Pigeons’ memory for sequences of light flashes when gap duration is an unreliable discriminative cue
In Experiment 1, pigeons were trained with a 1-sec dark and a 1-sec houselight-illuminated delay interval to discriminate
between sequences of two and four flashes of light (feeder illumination). The sequences could be discriminated on the basis
of the number of flashes, the number of gaps, or the duration of the gap between flashes. A choose-few bias was obtained at
extended dark delays, but not at extended illuminated delays. Pigeons appeared to confuse long dark delays with the longer
gap between flashes on few-sample trials. In Experiment 2, additional sample sequences were included that made gap duration
an unreliable cue for discriminating between the few and many samples. A significant choose-many bias was obtained at extended
dark delay intervals, but no biased forgetting was found at extended illuminated delays. The pigeons appeared to discriminate
light flash sequences by relying on multiple temporal features of a sequence rather than using an event switch to count flashes.
The biased-forgetting effects observed appear to be due to instructional ambiguity that results from the similarity of the
delay interval to features of the flash sequences. nt]mis|This research was supported by Grant OGPOOD6378 from the Natural
Sciences and Engineering Research Council of Canada to A.S. 相似文献
12.
Pigeons categorized binomial samples. One of two “coins” was tossed on each trial, and birds learned to infer from observing the outcomes which of the two equally likely coins had been tossed. Outcomes (“heads” or “tails”) appeared as successively presented red or green center keys. Coin R was biased in favor of red, and coin G was similarly biased in favor of green. A categorization consisted of a choice of a left or right side key and was reinforced with food if it was to the key (left for coin R and right for coin G) corresponding to the coin that produced that trial’s sample. Coin bias and minimum sample size required for reinforcement were experimentally manipulated. When sample size was greatest (n=8), categorizing a sample as having been produced by coin R tended to undermatch the probability that the sample was produced by coin R. When sample size was smallest (n=1), categorizing a sample overmatched, provided that the context did not include other trials with large samples. This context effect reconciles an otherwise inconsistent literature on intuitive statistical inference in pigeons but suggests a new and difficult goal for research-the general clarification of the effects of sampling context on inference. 相似文献
13.
Each of four pigeons was exposed to a single random-ratio schedule of reinforcement in which the probability of reinforcement
for a peck on either of two keys was 1/25. Reinforcer amounts were determined by an iterated prisoner’s dilemma (IPD) matrix
in which the “other player” (a computer) playedtit-for-tat. One key served as thecooperation(C) key; the other served as thedefection(D) key. If a peck was scheduled to be reinforced and the D-key was pecked, the immediate reinforcer of that peck was always
higher than it would have been had the C-key been pecked. However, if the C-key was pecked and thefollowing peck was scheduled to be reinforced, reinforcement amount for pecks on either key were higher than they would have been if
the previous peck had been on the D-key. Although immediate reinforcement was always higher for D-pecks, the overall reinforcement
rate increased linearly with the proportion of C-pecks. C-pecks thus constituted a form of self-control. All the pigeons initially
defected with this procedure. However, when feedback signals were introduced that indicated which key had last been pecked,cooperation (relative rate of C-pecks)—hence, self-control—increased for all the pigeons. 相似文献
14.
In Experiment 1, pigeons were trained in a within-subjects design to discriminate sequences of light flashes (illumination of the feeder) that varied in number, but not in time (2f/4sec and 8f/4sec), and in time, but not in number (4f/2sec and 4f/8sec). Number samples required a response to one of two comparison dimensions (either color or line), whereas time samples required a response to the remaining comparison dimension. Delay testing revealed a significant choose-small bias following number samples and a significant choose-long bias following time samples. In Experiment 2, testing confirmed that in the absence of a sample, there was a bias to respond small to the number comparisons and long to the time comparisons. Additional tests indicated that the birds were discriminating time samples on the basis of the number of light flashes occurring during the last few seconds of the time samples, rather than on the basis of the total duration of the flash sequence. Consequently, the choose-long bias observed for time samples during delay testing was really a choose-small bias. In Experiment 3, the birds received baseline training with a 5-sec delay and were subsequently tested at shorter and longer delays. A choose-large bias occurred at delays shorter than the baseline training delay, whereas a choose-small bias was again observed at delays longer than the baseline delay. These findings provide additional empirical support for the conceptualizing of memory for number and time in terms of a common mechanism. 相似文献
15.
Frans van Haaren 《Learning & behavior》1981,9(3):425-431
The effects of changeover delays of fixed or variable duration on concurrent variable-interval performance in pigeons were investigated in a series of three experiments. Experiment 1 compared the effects of a fixed, variable, or variable signaled changeover delay on interchangeover times and responding during and after the changeover delay. The duration of the changeover delays was systematically varied in Experiment 2, and the relative reinforcement frequencies were manipulated in Experiment 3. Interchangeover times were found to be shorter when changeover delays of variable duration were compared with those of fixed duration. Changeover delays of fixed duration produced higher response rates during the changeover delay than after the changeover delay had elapsed; changeover delays of variable duration produced such differences to a lesser extent. It was concluded that the changeover delay in concurrent variable-interval schedules of reinforcement functionally acts as a delay period to the next opportunity for reinforcement, possibly serving as a conditioned reinforcer for the behavior preceding it (the interchangeover time) and as a discriminative stimulus for the behavior in its presence (response rates during the delay). 相似文献
16.
Rats increased eating that produced access to a running-wheel or increased running that produced access to food, depending on which response was potentially deprived, relative to baseline, by the scheduled ratio of responding. Under both schedules, instrumental responding significantly exceeded appropriate baselines of the noncontingent effects of the schedule. The results contradicted the hypothesis that reinforcement is produced by an overall or momentary probability differential between two responses; instead, they supported the condition of response deprivation as a key determinant of reinforcement. Of several recent quantitative models that predict reversibility of reinforcement by schedule changes, only the predictions of the relative response-deprivation model did not differ significantly from the data of either schedule. 相似文献
17.
Two groups of pigeons were trained to perform symbolic delayed matching-to-sample at a 0-sec delay with sample stimuli that consisted of sequences of light flashes. The sequences varied in number but not time for one group (number group) and in time but not number for the other group (time group). When retention was tested at delays up to 10 sec in Experiment 1, a choose-small effect was found in the number group, and a choose-long effect was found in the time group. Transfer tests between number and time samples in Experiment 2 supported the hypothesis that pigeons were discriminating between the number of light flashes at the end of sample sequences in Experiment 1. It was concluded that pigeons in both the number and the time groups were discriminating between number of flashes and that the apparent choose-long effect was actually a choose-small effect. The implications of these findings for the mode-control model of counting and timing (Meck & Church, 1983) were discussed. 相似文献
18.
Frances K. McSweeney 《Learning & behavior》1992,20(2):160-169
Rats pressed levers for Noyes pellets or keys for sweetened condensed milk reinforcers delivered by multiple schedules. Session length and baseline rates of reinforcement were varied in two experiments. Rates of responding increased during the early part of the session and then decreased for both responses and reinforcers, as well as for all subjects and values of the independent variables. Changes in response rates across the session sometimes exceeded 500%. Respoiise rates peaked approximately 20 min after the beginning of the session, regardless of session duration, when subjects responded on a multiple variable interval 1-min variable interval 1-min schedule. The function was flatter for longer sessions than it was for shorter sessions. The function was flatter, more symmetrical, and peaked later for lower rates of reinforcement than for higher rates of reinforcement. The function appeared early in training, and further experience moved and reduced its peak. Variables related to reinforcement exerted more control over some aspects of this function than did variables related to responding. These within-session patterns of responding may have fundamental implications for experimental design and theorizing. 相似文献
19.
Pigeons’ preference between fixed-interval and variable-interval schedules was examined using a concurrent-chains procedure. Responses to two concurrently available keys in the initial links of the concurrent chains occasionally produced terminal links where further responses were reinforced under either a fixed- or variable-interval schedule. In previous studies, preferences for the variable schedule with such a procedure have been interpreted as reflecting atemporal scaling process that heavily weights the shorter intervals in the variable schedule. The present experiment examined whetherpredictability, i.e., the presence of external stimuli correlated with the reinforcement interval, might also influence preference in such situations. When the two intervals in a variable schedule were made predictable by being associated with different key colors, preference for that schedule increased. This increase was reliable but small in magnitude and transient when initial-link responses only occasionally produced terminal links; it was large in magnitude when only one response in the initial link was required to produce the appropriate terminal-link schedule. The results suggest that preference between fixed and variable schedules may be influenced both by temporal scaling and to a lesser extent by predictability of the reinforcement intervals. 相似文献
20.
Charles P. Shimp 《Learning & behavior》1982,10(3):358-364
In two experiments, pigeons pecked side keys in a discrete-trials setting in which shorter and longer runs of successive pecks on the left key before a switch to the right key occasionally produced, after a brief retention interval, a short-term memory probe for the most recent run length. In Experiment 1, a probe involved red and green side keys. A peck to a green (red) key was reinforced if the previous run length was shorter (longer). The dependent variable was the probability of a peck to the correct color. In Experiment 2, a probe involved an autoshaping procedure in which a response-noncontingent reinforcer was delivered after a 5-sec presentation of a green (red) center key if the previous run had been a shorter (longer) one. A reinforcer was not delivered when a red key followed a shorter pattern or a green key followed a longer pattern. The production of runs conformed to many previous molecular data on the way the local temporal patterning of behavior adapts to, that is, displays knowledge of, a reinforcement contingency. The probe results showed that a pigeon can report which of two run lengths it recently has emitted. Thus, a pigeon can, in a sense, describe its own adaptive behavior. Since the adaptive behavioral patterning on the center key may be said to represent knowledge, and since the probe behavior is a self-characterization or self-report by the organism about this knowledge, the probe behavior may be said to represent knowledge about knowledge, or metaknowledge. The data extend previous work on metaknowledge in the pigeon to a third type of adaptive temporal pattern of behavior, that is, run length (instead of response duration and interresponse time), and provide a second type of probe procedure, that is, autoshaping, by means of which a nonverbal organism can be asked what it knows about what it is doing to adapt to an environmental contingency. 相似文献