An analysis of serial pattern learning by rats

When rats receive a sequence of rewards of different magnitudes for traversing a runway, they learn to “track” the sequence, showing anticipation of the forthcoming reward by appropriate running speed. There is disagreement as to whether this behavior depends on rats’ encoding and recalling a complete sequence of foregoing hedonic events or just the immediately preceding one. The present experiments showed that rats can remember more hedonic events than the most recent one. In Experiment 1, when exposed concurrently to the sequences 10-1-0 (pellets) and 0-1-10, they were faster on Run 3 of the increasing than of the decreasing sequence, a discrimination which cannot be made on the basis of the preceding (1-pellet) reward alone. Experiment 2 showed that this behavior reflects genuine anticipation of the Run 3 reward, not simultaneous contrast or other simple aftereffects of Runs 1 and 2. It is argued, however, that these results, together with related findings by Capaldi and Verry (1981), show merely that rats can recall a hedonic event other than the most recent one, not that a sequence of such events is fully recalled in order.     

Integration and representation in rats’ serial pattern learning in the T-maze

Rats were exposed to three-trial series consisting of reinforced (R) trials and one nonreinforced (N) trial in a fixed order, RRN and RNR (Experiments 1 and 2) or NRR and RRN (Experiment 3), on extended visually distinct runways in a T-maze. When initially presented with the same sequence on each series in a session (separate presentations) with the same runway on all trials within a series (Experiments 1 and 3), all the rats developed slower running speeds on N than on R trials. When a runway was sometimes changed between the first and next two trials during separate presentations training (Experiment 2) or both sequences were later intermixed within each session in each experiment, only rats exposed to each sequence on a specific runway maintained these serial running patterns. Rats displayed serial running patterns on a test RNN sequence similar to that on the RNR sequence (Experiment 2), as would be predicted by an intertrial association model of serial pattern learning (Capaldi & Molina, 1979), but responded on test RRR and NRN sequences (Experiment 3) as would be predicted by an ordinal-trialtag/intratrial association model (Burns, Wiley, & Payne, 1986). Results from test series of free-choice trials in Experiments 1 and 2 failed to support a prediction of the intratrial association model that these rats would integrate RRN and RNR sequences. Rather than always selecting a baited runway on both the second and the third free-choice trials, the rats only selected a baited runway on the third trial on the basis of their choice on the second trial, as would be predicted by the intertrial association model. Only after experiencing all possible outcome sequences during forced-choice training in Experiment 3 did these rats predominantly select a baited runway on every free-choice trial.     

Serial learning and transfer in rats: Effects of changes in stimulus-stimulus associations,pattern structure,and serial position information

Four groups of rats (n=6 per group) were trained in a runway on a serial learning task. Groups were treated identically in Phase 1, receiving two daily presentations of a five-element series consisting of decreasing numbers of .045-g food pellets over successive runs, for example, 14-7-3-1-0. All groups learned to anticipate, and run slowly to, the terminal 0-pellet element, behavior that has been attributed to learning of a less-than rule, stimulus-stimulus (S-S) associations, and knowledge of the serial position of items. In Phase 2, subjects were transferred to one of four test series: 20-14-7-3-0,20-7-3-14-0, 20-14-7-3-1-0, or 20-7-14-3-1-0. Anticipation was disrupted on the first two series, which maintained the integrity of serial position information and in the first case the less-than rule, but eliminated the terminal portion of the associative chain. Anticipation was unimpaired by transfer to either of the last two series. These series maintained the integrity of the terminal 3-1-0 portion of the associative chain but presented altered information about serial position, and in the last case also altered the less-than rule. The results, which supported the memory-discrimination model of rat serial learning, are discussed with reference to related transfer experiments in human serial learning.     

Memory,serial anticipation pattern learning,and transfer in rats

Learning & Behavior - Three experiments tested hypotheses about whether rats respond appropriately to, or track, an orderly series of reward magnitudes terminating in nonreward by encoding the...     

Difficult serial anticipation learning in rats: Rule-encoding vs. memory

Rats, trained in a runway, were asked to anticipate, while running slowly, the last two events in repeating series of .045-g food pellets. The series were either weakly monotonic (14, 5, 5, 1, and then 0 pellets/run) or nonmonotonic (5-5-14-1-0). While the terminal 0-pellet event was better anticipated in the weakly monotonic series, the reverse was the case for the next-to-last 1-pellet event. These findings were expected from a memory-discrimination learning hypothesis of serial learning, which suggests that the memory of one event in a series can be used to signal the next event. However, the better anticipation of the 1-pellet event by the nonmonotonic group was inconsistent with the recently stated rule-encoding position of Hulse (1980). According to that view, difficult series of the sort employed in the present investigation are learned by encoding the rule structure of the series, with events in the series with the simple rule structure (the weakly monotonic series in this investigation) being better anticipated than events in the series with the complex rule structure.     

Formal structure and pattern length in serial pattern learning by rats

When rats learn to anticipate a sequence of stimulus events, such as a serial pattern of different food quantities, they are sensitive to the rule-based formal structure relating the magnitude of successive stimuli. Earlier research has shown that if formal structure is simple (e.g., if a single “less than” rule relates the size of each successive quantity), patterns are learned faster than if formal structure is complex (e.g., if two or more rules such as “less than” and “greater than” relate successive pattern quantities). Two experiments tested the hypothesis that pattern length modulates the role of pattern complexity. We predicted that pattern length and pattern complexity interact in determining pattern difficulty. That is to say, long complex patterns should be learned more slowly than short complex patterns. However, long simple patterns should be learned faster than short simple patterns. In Experiment 1, rats ran a straight runway to receive repeated sequences of food quantities. The long-monotonic group received a formally simple 18-10-6-3-1-0 pattern, in which each number represents a quantity of food pellets. The long-nonmonotonic group received a formally complex 10-1-3-6-18-0 pattern. Similarly, the short-monotonic and short-nonmonotonic groups received 18-1-0 and 1-18-0 patterns. Pattern tracking—fast and slow running in anticipation of large and small quantities of food, respectively—was taken as an index of pattern learning. In Experiment 2, comparable patterns were used, but rats leverpressed in a discrete-trial procedure; response latencies measured pattern tracking. In both experiments, rats learned formally simple patterns faster than they did formally complex patterns. In Experiments 1 and 2, but less clearly in Experiment 2, the predicted interaction was obtained. The results support and generalize the idea that rats encode and use some representation of the formal rule structure of serial patterns as they learn them.     

Generalization of serial learning in the pigeon

Sequence learning in pigeons was studied in asimultaneous chaining paradigm: all stimuli and the opportunity to respond to each stimulus were available simultaneously. In contrast to the traditionalsuccessive chaining paradigm, a simultaneous chaining paradigm provides no differential feedback following each response (except the last). Subjects were first trained to perform on sequences of two (AB), then three (ABC), and then four colors (ABCD). Performance greatly exceeded that predicted by models of random choice. Generalization to novel arrays of three and four colors was complete. After training with a four-color sequence, the subjects were tested with subsequences consisting of all possible combinations of two and three of the four training colors (e.g., BD, AD, BC, ACD, BCD, etc.). The successful completion of these subsequences showed that the organization of the original sequence did not entail overt pecks to successive elements of that sequence. That subjects can respond accurately on nonadjacent subsets is not readily explained by a chaining theory, or by any theory that assumes that responding to element n provides a cue for responding to element n+1.     

The representation of items in serial position

Four experiments with rats tested their ability to anticipate serial patterns made from elements of reward magnitudes (14, 7, 3, 1, or 0 food pellets). Anticipation was measured by the running time in a straight alley. Elements arranged in a monotonically descending pattern were more easily anticipated than were the same elements arranged in a nonmonotonic pattern. Better anticipation was also observed when training utilized four trials per day with short interrun intervals (10–15 sec), spent in the startbox of the runway, than when training utilized one trial per day with long interrun intervals (4–5 min), spent in the rat’s home cage. Anticipation of the monotonie sequence was also superior when training consisted of one trial per day with a short interrun interval relative to that observed with four trials per day and a long interrun interval. Following acquisition of anticipation of the monotonie sequence with a short interrun interval, transfer to the same sequence with a long interrun interval resulted in disruption of anticipation. Finally, anticipation of a well-learned monotonie sequence was not disrupted by replacement of individual rewarded elements in the sequence with a 0-pellet element. These experiments indicate that the duration between runs of a trial, but not that between trials or the number of trials per day, is important in the formation of serial expectancies. They also suggest that the rats come to represent the sequence as items in serial position.     

Effects of interrun interval on serial learning

Two groups of five rats each received a decreasing quantity of food reward, 14-7-3-1-0 .045-g food pellets, over successive runs in a runway. The interrun interval (IRI) separating runs within each of two daily pattern repetitions (trials) was 10 sec (short, S) or 4–5 min (long, L) and varied over four successive phases of training in the order indicated by the group names, that is, Groups SLSS and LLLS. Anticipation of the 0-pellet element developed more rapidly in Group SLSS than in Group LLLS, but did eventually occur at the long IRI. Anticipation was eliminated by the increase in IRI experienced by Group SLSS in Phase 2 and by the decrease in IRI experienced by Group LLLS in Phase 4. The results are discussed with reference to the effects of changes in stimulus context accompanying IRI shifts on retrieval of task-specific knowledge and with reference to the possible signal value established to IRI-specific stimuli.     

Stimulus control of anticipatory responding in instrumental learning as revealed in serial learning tasks

Items in a fixed series A-B-C can be anticipated employing either item information (e.g., ItemA cues signal Item B) or position information (e.g., Position 2 cues signal Item B). Identical fixed series of rewarded and nonrewarded trials were employed in investigations reported by Capaldi and Miller (1988), Capaldi, Alptekin, Miller, and Birmingham (1997), and Burns, Dunkman, and Detloff (1999). These series were learned employing item cues according to Capaldi and colleagues and position cues according to Burns et al. (1999). Burns et al.’s (1999) conclusions were based on rats’ behavior when shifted to novel series, which could reveal position learning but not item learning. Employing the acquisition conditions of Burns and co-workers but shifts to series that could reveal item learning, evidence for item learning was obtained in two experiments. The most reasonable interpretation of the above set of findings is that rats employ a compound of both types of cues to signal items. To our knowledge, no set of prior findings so strongly suggests a similar conclusion.     

Extrapolation of serial stimulus patterns by rats

This experiment determined if rats could extrapolate a familiar serial sequence of diminishing food quantities by accurately anticipating a novel quantity added to the end of the sequence. In 13 days of training, rats ran in a straight runway to obtain quantities of food pellets presented in sequential order. A strongly monotonic group received repetitions of a formally simple pattern of 14-7-3-1 pellets of food, while weakly monotonic and nonmonotonic groups received formally more complex 14-5-5-1 and 14-3-7-1 patterns, respectively. In subsequent transfer, a 0-pellet quantity was added to each pattern, thus extending pattern length to five elements. Results of the very first pattern repetition containing the added 0-pellet element indicated that rats in the strongly monotonic condition, but not in the others, anticipated the reduced quantity before actually experiencing it. This result supports a cognitive, rule-learning hypothesis for serial learning by rats.     

Dissociations between serial position and number of letters effects in lateralised visual word recognition

Some previous studies of visual word recognition have reported an interaction between visual field and word length (measured by number of letters), such that recognition is affected more by word length for words presented in the left than for words presented in the right visual field. However, when manipulating serial position of letters in words to measure length effects, there are also reports of symmetrical word length effects in the two visual fields. Here we report two experiments, presenting four‐ and seven‐letter words, suggesting that the serial position and length effects in the hemispheres are separable and task dependent. For tasks that rely more heavily on letter‐level processing such as letter search (Experiment 1), performance in both hemifields showed similar effects of serial position; however, when comparing four‐ and seven‐letter words, an effect of word length was evident only in the left visual field, in line with the well‐established interaction between word length and hemifield. An interaction between word length and hemifield was confirmed for the same stimuli when they were employed in a lexical decision task, which forced whole‐word processing (Experiment 2). We conclude that the effects of serial position and number of letters in the two visual fields are separable, and are selectively affected by task type.     

Concurrent object-discrimination learning in rats

Investigations employing primates have sometimes used tests of concurrent object-discrimination as indexes of multiproblem memory in comparative studies of neuropathological impairment. The present investigation was an attempt to employ a comparable test procedure with rats. Data from two experiments indicated that rats could indeed be trained on a concurrent object-discrimination task. Furthermore, results from the second experiment indicated that these performances and brightness discriminations shared the property of disruption by posterior decortication. Implications for the neuropsychology of learning and memory are discussed.     

Intratrial proactive interference in rats’ serial alternation performance in the radial maze

Rats acquired a serial alternation task in an eight-arm radial maze that was partitioned into four pairs of arms. Each pair was associated with a different distal stimulus. Rats were initially forced to the left or right arm in each pair (the study segment) before being exposed to both arms in each pair (the free-choice or test segment). Only the previously blocked arm of each pair remained baited. Following initial training, proactive interference (PI) was induced by presenting rats with a forced-choice (prestudy) segment containing arm positions opposite those in the subsequent study segment. Such trials generated poorer free-choice accuracy than did trials without a prestudy segment. Forcing rats to both arms in the pair in a prestudy segment produced only transient PI. A slight improvement in rats’ free-choice performance was obtained by forcing them to the same arm position, but only when the test segment was delayed by 30 min. Increasing the interval between the prestudy and study segments from 2 to 30 min eliminated PI, but only when free-choice testing was delayed by 2 min rather than by 30 min. These results suggest that intratrial PI in this preparation was primarily due to confusion about which arm position in each pair had been visited during the last forced-choice segment.     

An examination into some variables said to affect serial learning

In each of three serial learning investigations, rats in a runway were given varying numbers of 0.045-g food pellets in a fixed order. Serial learning was indexed by faster running to larger than to smaller reward quantities. It has been suggested by Hulse (Animal Learning & Behavior, 1980,8, 689–690) and by Roitblat (Behavioral Brain Sciences, 1982,5, 353–371) that differences between two or more serial learning groups that have been obtained under one set of specified experimental conditions may be completely reversed or eliminated under another set of specified experimental conditions. In each of the three investigations reported here, we examined series that had been compared in previous investigations, employing, however, experimental conditions that, according to Hulse and to Roitblat, should produce results different from those obtained previously. In each of the three investigations reported here, the groups differed as they had previously. The findings obtained in this report suggest that none of the following variables is critical to the results obtained in serial learning investigation in the sense suggested by Hulse and Roitblat: the number of items contained in the series, the number of times the series is presented each day, the temporal interval elapsing between items, and the temporal interval elapsing between series presentations. The implications of the present findings for the rule-encoding view of Hulse and his coworkers and for the memory-discrimination learning view of Capaldi and his coworkers are examined.     

环序数和序数差对牛顿环测量透镜曲率半径的影响研究

针对学生在牛顿环实验中提出的问题,本文通过对实验数据处理进行分析,指出牛顿环实验数据采集和数据处理过程中选取环序数和序数差应注意事项,并指出在数据处理过程中使用绘图拟合软件Origin进行线性拟公得到曲率半径的方法是可行的.     

Place versus response learning in rats

In previous research designed to test whether place learning or response learning proceeds more quickly and better in rats,place has not been defined unambiguously when direction has been controlled by moving an apparatus around in the test room (Blodgett, McCutchan, & Mathews, 1949; Skinner et al., 2003). In Experiment 1, we compared place and response learning while controlling direction in a static apparatus, thus making the meaning of place unambiguous. The performance of rats that had to make different turns to find food in a particular place and rats that had to always make the same turn to find food in two different places did not differ. In Experiment 2, visual cues were made equally discriminable for place and response learners in a static apparatus. Place learners still failed to outperform response learners, but there was evidence that response biases interfered more with place than with response learning. The results are discussed with reference to the historical debate that generated the original research and also in terms of more contemporary spatial-learning issues in rats.     

Associative foundation of causal learning in rats

Are humans unique in their ability to interpret exogenous events as causes? We addressed this question by observing the behavior of rats for indications of causal learning. Within an operant motor–sensory preconditioning paradigm, associative surgical techniques revealed that rats attempted to control an outcome (i.e., a potential effect) by manipulating a potential exogenous cause (i.e., an intervention). Rats were able to generate an innocuous auditory stimulus. This stimulus was then paired with an aversive stimulus. The animals subsequently avoided potential generation of the predictive cue, but not if the aversive stimulus was subsequently devalued or the predictive cue was extinguished (Exp. 1). In Experiment 2, we demonstrated that the aversive stimulus we used was in fact aversive, that it was subject to devaluation, that the cue–aversive stimulus pairings did make the cue a conditioned stimulus, and that the cue was subject to extinction. In Experiments 3 and 4, we established that the decrease in leverpressing observed in Experiment 1 was goal-directed instrumental behavior rather than purely a product of Pavlovian conditioning. To the extent that interventions suggest causal reasoning, it appears that causal reasoning can be based on associations between contiguous exogenous events. Thus, contiguity appears capable of establishing causal relationships between exogenous events. Our results challenge the widely held view that causal learning is uniquely human, and suggest that causal learning is explicable in an associative framework.