Rule abstraction, item memory, and chunking in rat serial-pattern tracking

Two studies used a stimulus tracking paradigm to test whether rats are sensitive to the rule-based formal properties of structured serial patterns. Hooded rats tracked 16-element patterns of flashing lights by pressing levers under an array of 6 indicator lights. In Experiment 1, rats tracked a pattern similar to one previously used with human subjects and yielded remarkably similar results. More errors and response omissions occurred at boundaries of structural "chunks" than within chunks, and errors often reflected anticipation of the next chunk or extrapolation of the preceding chunk. In Experiment 2, temporal "phrasing" cues encouraged different groups to encode a pattern as a series of either "runs" or "trills." Differential placement of pauses induced rats to encode different rule-based representations of the pattern. Results indicate that under appropriate conditions rats may encode a representation of formal structure when they learn organized response patterns.     

Concurrent Cognitive Processes in Rat Serial Pattern Learning: Item Memory, Serial Position, and Pattern Structure

Three experiments examined the processes mediating rat serial pattern learning for rule-consistent versus rule-violating pattern elements (“violation elements”). In all three experiments, rats were trained to press retractable levers in a circular array in a specific sequence for brain-stimulation reward (BSR). Experiment 1 examined the role of lever location (L) and element serial position (SP) cues in rats’ ability to learn to anticipate a violation element positioned at the end of a 24-element serial pattern. Rats with L cues either alone or in combination with SP cues learned to anticipate the violation element, whereas those with SP cues alone did not. Rats in groups L and L + SP underwent a series of transfers designed to remove various cues that might have controlled their performance on the violation element. Results indicated that intra-chamber lever location cues mediated performance on the violation element whereas performance on rule-consistent elements within pattern chunks was mediated by an internal mnemonic representation that was insensitive to changes in lever location cues. Experiment 2 examined whether rats could learn to use SP cues alone to anticipate a violation element if it was positioned earlier in a serial pattern. Rats learned to anticipate the violation element based on SP cues alone when it was located in SP6 in a 24-element pattern, but not when it was in SP12. Experiment 3 examined whether or not rats spontaneously encode information about chunk length and the serial position of phrasing cues in serial patterns. Rats were trained to a high criterion on the serial pattern used in Experiment 1, then were challenged with three probe patterns that manipulated both chunk length and overall pattern length. Results indicated that rats spontaneously encoded information regarding the serial position of phrasing cues in relation to chunk length. Thus, rats appear to use at least three cognitive processes concurrently in serial pattern learning tasks, namely, item memory involving external discriminative cues, counting- or timing-like processes for encoding serial position, and rule abstraction for encoding an internal representation of pattern structure.     

Concurrent cognitive processes in rat serial pattern learning: II. Discrimination learning,rule learning,chunk length,and multiple‐item memories

The current experiment examined the factors that determine acquisition for elements of highly structured serial patterns. Three groups of rats were trained on three patterns with parallel rule‐based hierarchical structure, but with 3‐, 4‐, or 5‐element chunks, each with a final violation element. Once rats mastered their patterns, probe patterns were introduced to answer several questions. To assess the extent to which the learned response pattern depended on intrachamber location cues for anticipating different element types, Spatial Shift Probes shifted the starting lever of patterns to locations that positioned chunk boundaries where they had never been experienced during training. To assess the extent to which a phrasing cue is necessary for rats to perform a chunk‐boundary response, a Cue Removal Probe tested whether rats would produce a chunk‐boundary response in the correct serial position if the phrasing cue was omitted. To assess the extent to which cues from multiple trials leading up to the violation element are required to anticipate the violation element, Multiple‐Item Memory Probes required rats to make an unexpected response on one of the elements in the last two chunks of the pattern prior to the violation element. The results indicated that rats used multiple concurrent learning and memory processes to master serial patterns, including discrimination learning, rule learning, encoding of chunk length, and multiple‐item memories.     

Number, But Not Rhythmicity, of Temporal Cues Determines Phrasing Effects in Rat Serial-Pattern Learning

Recent work on experimental manipulations that affect chunking in sequential learning has shown that cues inserted into a sequence, termed “phrasing cues,” can facilitate learning by serving as discriminative cues that overshadow associations between sequence items (Stempowski, Carman, & Fountain, 1999). This experiment assessed whether rhythmicity is an important determinant of temporal phrasing effects or, instead, that a discrimination learning view can adequately account for the results of manipulating the number and sequential positioning of phrasing cues. Rats learned serial patterns in which the number and organization of phrasing cues were manipulated so that phrasing cues were positioned at the beginning of four or eight chunks in an eight-chunk serial pattern. Alternate Chunks phrasing, Aperiodic phrasing (four cues always positioned before the first, third, fourth, and seventh chunks), and Random phrasing (four cues positioned at four chunks chosen randomly for each new pattern presentation) produced equal facilitation of acquisition for cued chunks relative to a No Phrasing condition, but not as much facilitation as Every Chunk phrasing. Cue removal produced deficits, with greater impairment observed for the eight- versus four-cue conditions. Thus, the effects of temporal phrasing cues were predicted less by their rhythmicity than by the common discrimination learning notion that associative strength is a function of the number of stimulus–response pairings.     

The roles of outcome and position associations in animal serial learning

Evidence that outcome associations, position associations, and response patterns each contribute to performance in animal serial learning came from two experiments in which three-trial series of rewarded and not-rewarded trials were examined. Response patterns were disrupted in Experiment 1 by placing animals directly in the goal on selected trials, a procedure that reduced (favoring outcome associations) but did not eliminate (favoring position associations) serial behavior. Series constructed to make outcome associations impossible (Experiment 2) produced serial behavior that indicated salient position associations can serve as phrasing cues to chunk the position information contained in the series.     

The role of Gestalt grouping principles in visual statistical learning

A major issue in visual scene recognition involves the extraction of recurring chunks from a sequence of complex scenes. Previous studies have suggested that this kind of learning is accomplished according to Bayesian principles that constrain the types of extracted chunks. Here we show that perceptual grouping cues are also incorporated in this Bayesian model, providing additional evidence for the possible span of chunks. Experiment 1 replicates previous results showing that observers can learn three-element chunks without learning smaller, two-element chunks embedded within them. Experiment 2 shows that the very same embedded chunks are learned if they are grouped by perceptual cues, suggesting that perceptual grouping cues play an important role in chunk extraction from complex scenes.     

Behaviour of Rats During Selfinitiated Pauses in Feeding and Drinking, and During Periodic Response-Independent Delivery of Food and Water

In Experiment I rats deprived of either food or water were given free access to food or water respectively, and their behaviour was observed during self-imposed pauses in feeding or drinking. In Experiment II food or water were delivered according to fixed-time 30-s and fixed-time 60-s schedules, and the behaviour of the rats was observed during the interreinforcement intervals imposed by these schedules. In both experiments the temporal pattern of those activities that occurred during pauses in eating differed from the pattern of activities occurring during pauses in drinking; and with both food and water the temporal pattern of activities during self-imposed pauses in consummatory behaviour in Experiment I proved a good predictor of the pattern of activities during schedule-imposed interreinforcement intervals in Experiment II. This suggests that intermittent schedules permit the occurrence of those activities that are normally closely associated with the consummatory behaviour in question. In Experiment II certain activities that occurred towards the end of the interreinforcement interval were found to be enhanced relative to baseline level, but there was no enhancement of activities occurring near the beginning of the interval. This is contrary to Staddon's (1977) account of schedule-induced behaviour, and suggests that schedule-induction is not as common as has sometimes been supposed.     

Adult age differences in the rate of learning serial patterns: evidence from direct and indirect tests.

Subjects performed a serial reaction time task (adopted from Nissen & Bullemer, 1987) that contained a repeating pattern of spatial locations. In Experiment 1, following 20 repetitions of a 10- or 16-element pattern, reaction time was equally disrupted for both younger and older people when the sequence became random. In Experiment 2, the response times for subjects encountering the 10-element pattern were compared with those of subjects encountering a random sequence. These response time functions diverged at the same point in training for the 2 age groups. Thus, on this indirect measure of response time facilitation, both experiments revealed age similarity in the rate of pattern learning. In contrast, on a subsequent direct test of pattern learning that required prediction, the younger people earned a higher percentage correct score than the older in both experiments. Age-related dissociations between direct and indirect measures of learning and comparisons with memory-impaired populations are discussed.     

A multiple species approach to sequential learning: Are you a man or a mouse?

We have developed a method for studying list learning in animals and humans, and we use variants of the task to examine list learning in rats, mice, and humans. This method holds several advantages over other methods. It has been found to be easily learned without lengthy pretraining. The data gathered with this procedure provide a measure of correct response rates, of incorrect responses and the locations of these responses, and of response latency on a trial-by-trialbasis. We have examined mouse, rat, and human list acquisition of patterns ranging from 12 to 48 items in length. This procedure has also been used to examine many aspects of list learning, such as the effects of the placement of phrasing cues that are either consistent or inconsistent with the structure of the list in rats and mice, the effects of phrasing cues of differing modalities in mice, the sensitivity of subjects to violations of list structure in rats, subjects’ abilities to “chunk” from nonadjacent serial positions in structured lists in rats, and subjects’ sensitivity to serial patterns with multiple levels of hierarchical organization. The procedure has also been used to examine the effects of drugs on sequential learning.     

Chunking, rule learning, and multiple item memory in rat interleaved serial pattern learning

Nonhuman animals, like humans, appear sensitive to the structure of the elements of sequences, perhaps even when the structure relates nonadjacent elements. In the present study, we examined the contribution of chunking, rule learning, and item memory when rats learned serial patterns composed of two interleaved subpatterns. In one group, the first interleaved subpattern was a formally simple sequence, whereas in two other groups the first subpattern was formally more complex, containing 2 or 4 violation elements, respectively. In all groups, the second interleaved subpattern encountered was formally simple. Evidence from the study suggests that rats chunked their interleaved patterns into component subpatterns, that is, they cognitively sorted pattern elements to form chunks based on nonadjacent structural relationships that can be characterized as rules. They also learned interitem associations via traditional discrimination learning to use adjacent elements as compound or configural cues for later events in the sequence. Thus, the evidence suggests that rats used chunking, rule learning, and interitem association learning concurrently to master these complex patterns.     

Offline Improvement during Motor Sequence Learning Is Not Restricted to Developing Motor Chunks

Robust offline performance gains, beyond those that would be anticipated by being exposed to additional physical practice, have been reported during procedural learning and have been attributed to enhancement consolidation, a process by which memory is transformed in such a way that it is not only more resistant to forgetting but may also involve a reorganization of information that supports superior task execution. The authors assessed the impact of increasing within-session practice extent on the emergence of offline performance gains. Practice-dependent improvements occurred across 12 and 24 30-s practice trials of a 5-element motor sequencing task. Offline improvements were observed following both 12 and 24 trials. The improvement following 12 trials was associated with the formation of motor chunks important for establishing movement sequence structure. In contrast, the offline improvement after 24 trials was not related to further changes in movement structure beyond those that had emerged during practice. These data suggest that additional memory operations, beyond those needed to amalgamate subsequences of the SRT task, are susceptible to enhancement consolidation.     

Learning of syllable-object relations by preverbal infants: The role of temporal synchrony and syllable distinctiveness

The role of temporal synchrony and syllable distinctiveness in preverbal infants’ learning of word-object relations was investigated. In Experiment 1, 7- and 8-month-olds (N = 64) were habituated under conditions where two similar-sounding syllables, /tah/ and /gah/, were spoken simultaneously with the motions of one of two sets of objects (synchronous) or out of phase with the motions (asynchronous). On test trials, 8-month-olds, but not 7-month-olds, showed learning of the relations in the synchronous condition but not in the asynchronous condition. Furthermore, in Experiment 2, following habituation to one of the synchronous syllable-object pairs, 7-month-olds (n = 8) discriminated the syllables and the objects. In Experiment 3, following habituation to two distinct syllables, /tah/-/gih/ or /gah/-/tih/, paired with identical objects, 7-month-olds (n = 40) showed learning of the relations, again only in the synchronous condition. Thus, synchrony, which mothers naturally provide between words and object motions, facilitated the mapping onto objects of similar-sounding syllables at 8 months of age and distinct syllables at 7 months of age. These findings suggest an interaction between infants’ synchrony and syllable distinctiveness perception during early word mapping development.     

The Effects of Feature Identity in Operant Serial Feature-Negative Discriminations

The effects of feature identity in an operant serial feature-negative discrimination (F1 T1−, T1+) were examined in two experiments with rats. In Experiment 1, rats were trained with two operant serial feature-negative discriminations in which different operants were reinforced during two auditory target cues (T1 and T2). The features (F1 and F2) were two neutral cues (visual or auditory stimuli), two motivationally significant cues (flavored sucrose solutions, also used as the operant reinforcers), or one neutral and one motivationally significant cue. Experiment 1 showed that discrimination acquisition, transfer performance, and feature–target interval testing were facilitated with a flavored sucrose feature. Experiment 2 showed that flavored sucrose-alone presentations, more than flavored sucrose trained in a pseudodiscrimination (F1 T1+, T1+), shared several similarities with a standard flavored sucrose feature. The results suggest flavored sucrose rapidly acquires inhibitory properties, which facilitates operant serial feature-negative discrimination performance.     

Retrospective revaluation effects in the conditioned suppression procedure

In four experiments using the conditioned suppression procedure, rats received initial reinforced training with two compound stimuli, AX and BY, each compound consisting of one auditory and one visual element. After a second phase of training consisting of nonreinforced presentations of A, the suppression governed by X and Y was tested. In Experiment 1 X evoked slightly less suppression than Y (a mediated extinction effect). This outcome was obtained when the auditory cues served as Xand Y(Experiment 1a), when the visual cues served as Xand Y(Experiment 1b), and when the number of nonreinforced presentations of Awas increased (Experiment 1c) from 18 to 216. In Experiment 2, however, in which the initial training was given with serial compounds (i.e., A ⇒ X and B ⇒ Y) X evoked more suppression than Y (a recovery-from-overshadowing effect). It was argued that extinction of A engages two learning processes, one increasing the effective associative strength of its associate (X) and one reducing it, and that the balance between these two depends on the specific conditions of training.     

测验与反馈在分段视频学习中的作用

分段原则是多媒体和视频学习中通过分段促进学习的重要原则。本研究探讨了测验和反馈对分段的影响。实验1对比了观看分段视频和在分段中进行测验两种情境,结果表明分段中测验会提高学习表现。实验2对比了分段视频、分段中测验和分段中测验并提供反馈三种情境。结果发现分段组与分段测验组之间没有差异,接受反馈的学习者学习表现最好。结果表明在分段视频中测验和反馈具有积极效应,对多媒体和线上学习具有潜在的意义。     

Place learning in scopolamine-treated rats: the roles of distal cues and catecholaminergic mediation

Experiments 1 and 2 tested the hypothesis that cholinergic receptor antagonists impair place learning in a water maze by interfering with the processing of distal, visual cues. Extramaze cues were offered to rats in the form of geometrical patterns arranged on the inner circumference of a curtain surrounding the water maze. In Experiment 1 the animals were offered both the distal cues and proximal cues in the form of pingpong balls in fixed positions on the surface of the water while only distal cues were present in Experiment 2. Animals were injected with either scopolamine (0.5 mg/kg body wt) or saline 20 min prior to the daily place learning sessions. Upon reaching criterion level performance the animals were tested on "rotation" sessions on which the distal cues were displaced. The outcome of such "rotations" demonstrated that-regardless of the presence or absence of proximal cues-scopolamine-treated rats relied at least as much as normal animals on the distal cues. The acquisition phase of both Experiments 1 and 2 demonstrated an almost complete lack of scopolamine-associated impairment in acquisition and performance of the place learning task. In Experiment 3 (when scopolamine was no longer administered) the subjects of Experiment 2 were exposed to a series of pharmacological "challenges" of their place learning performance and eventually to surgical ablation of the anteromedial prefrontal cortex. The outcome of the pharmacological challenges and the postoperative test of task performance demonstrated that the place learning performance of animals which had acquired the task under scopolamine was mediated by a neural substrate dissimilar to the substrate of task performance in normal animals. Rats acquiring the task while deprived of the cholinergic system demonstrated above-normal contributions to task mediation from catecholaminergic-probably dopaminergic-mechanisms and tentative results pointed to a "shift" toward prefrontal task mediation.     

Pigeons may not remember the stimuli that reinforced their recent behavior

In two experiments the conditioned reinforcing and delayed discriminative stimulus functions of stimuli that signal delays to reinforcement were studied. Pigeons' pecks to a center key produced delayed-matching-to-sample trials according to a variable-interval 60-s (or 30-s in 1 pigeon) schedule (Experiment 1) or a multiple variable-interval 20-s variable-interval 120-s schedule (Experiment 2). The trials consisted of a 2-s illumination of one of two sample key colors followed by delays ranging across phases from 0.1 to 27.0 s followed in turn by the presentation of matching and nonmatching comparison stimuli on the side keys. Pecks to the key color that matched the sample were reinforced with 4-s access to grain. Under some conditions of Experiment 1, pecks to nonmatching comparison stimuli produced a 4-s blackout and the start of the next interval. Under other conditions of Experiment 1 and each condition of Experiment 2, pecks to nonmatching stimuli had no effect and trials ended only when pigeons pecked the other, matching stimulus and received food. The functions relating pretrial response rates to delays differed markedly from those relating matching-to-sample accuracy to delays. Specifically, response rates remained relatively high until the longest delays (15.0 to 27.0 s) were arranged, at which point they fell to low levels. Matching accuracy was high at short delays, but fell to chance at delays between 3.0 and 9.0 s. In Experiment 2, both matching accuracy and response rates remained high over a wider range of delays in the variable-interval 120-s component relative to the variable-interval 20-s component. The difference in matching accuracy between the components was not due to an increased tendency in the variable-interval 20-s component toward proactive interference following short intervals. Thus, under these experimental conditions the conditioned reinforcing and the delayed discriminative functions of the sample stimulus depended on the same variables (delay and variable-interval value), but were nevertheless dissociated.     

Perceptual and positional saliencies influence children’s sequence learning differently with age and instructions at test

There is growing evidence that, faced with a complex environment, participants subdivide the incoming information into small perceptual units, called chunks. Although statistical properties have been identified as playing a key role in chunking, we wanted to determine whether perceptual (repetitions) and positional (initial units) features might provide immediate guidance for the parsing of information into chunks. Children aged 5 and 8 years were exposed to sequences of 3, 4, or 5 colours. Sequence learning was assessed either through an explicit generation test (Experiment 1) or through a recognition test (Experiment 2). Experiment 1 showed that perceptual and positional saliencies benefited learning and that sensitivity to repetitions was age dependent and permitted the formation of longer chunks (trigrams) in the oldest children. Experiment 2 suggested that children became sensitive to perceptual and positional saliencies regardless of age and that the both types of saliencies supported the formation of longer chunks in the oldest children. The discussion focuses on the multiple factors intervening in sequence learning and their differential effects as a function of the instructions used at test to assess sequence learning.     

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-trial-tag/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.     

Patterns, chunks, and hierarchies in serial reaction-time tasks

The impact of relational structures (i.e., the systematicity of relations between successive items) on incidental sequence learning was investigated in a serial reaction-time (SRT) task while keeping constant the statistical structure. In order to assess the influence of relational structures in stimulus and response sequences separately, the strength of relational patterns in sequences of digits as stimuli and of keystrokes as responses was orthogonally varied. In Exps. 1 and 2, the variation of relational patterns was mainly effective in the keystroke sequence. In Exp. 2, in addition to the variation of relational patterns, the presentation of stimuli was delayed at serial positions that were incongruent with the relational structure. The results show that these incongruent pauses reduced the learning of strongly structured sequences of keystrokes but improved the learning of weakly structured sequences. Experiment 3 suggests that even higher-order relations between elementary patterns are utilized to accelerate responses. The data are interpreted as evidence for the impact of relational patterns, in addition to statistical redundancies, on the formation of chunks. Reasons are discussed for the finding that relational chunking was more pronounced in the keystroke than in the digit sequences. Received: 25 June 1998 / Accepted: 3 December 1998