Implicit motor sequence learning is not purely perceptual

Many reports have indicated that implicit learning of sequences in a choice response time task is primarily perceptual; subjects learn the sequence of stimuli rather than the sequence of motor responses. Three experiments tested whether implicit motor sequence learning could be purely perceptual: no support was found for that hypothesis. Subjects who merely watched stimuli did not learn the sequence implicitly (Experiment 1), and sequence learning transferred robustly to a different set of stimulus cues (Experiment 2). In the final experiment, the stimulus-response mapping was changed at transfer so that one group of subjects pushed the same sequence of keys but saw new stimuli, whereas another group pushed a different sequence of keys but saw the same stimuli. Transfer to the new mapping was shown only if the motor sequence was kept constant, not the perceptual sequence. It is proposed that subjects learn a sequence of response locations in this and similar tasks.     

Is implicit learning perceptually inflexible? New evidence using a simple cued reaction-time task

Considerable research has been devoted to investigating learning without awareness. Burke and Roodenrys [Burke, D., & Roodenrys, S. (2000). Implicit learning in a simple cued reaction-time task. Learning and Motivation 31, 364–380] developed a simple learning task in which a cue shape predicts the arrival of a target shape (to which subjects respond) in a sequence of rapidly presented shapes, and found that all subjects responded faster to cued targets than to uncued targets, even those classified as unaware of the cue–target relationship. Two experiments were conducted to examine the perceptual flexibility of implicit (and explicit) learning using the paradigm developed by Burke and Roodenrys (2000). Perceptual flexibility was examined by altering the perceptual features of the cue shape. The results of the first experiment indicated the implicit, but not explicit, learning that occurs in this paradigm is perceptually inflexible. However, the second experiment indicated that perceptually flexible implicit learning can be encouraged by varying the nature of the experimental stimuli. These experiments therefore provide support for processing accounts of transfer.     

Verbal recoding of visual stimuli impairs mentalimagetransformations

Two experiments were carried out to test the hypothesis that verbal recoding of visual stimuli in short-term memory influences long-term memory encoding and impairs subsequent mental image operations. Easy and difficult-to-name stimuli were used. When rotated 90 degrees counterclockwise, each stimulus revealed a new pattern consisting of two capital letters joined together. In both experiments, subjects first learned a short series of stimuli and were then asked to rotate mental images of the stimuli in order to detect the hidden letters. In Experiment 1, articulatory suppression was used to prevent subjects from subvocal rehearsal when learning the stimuli, whereas in Experiment 2, verbal labels were presented with each stimulus during learning to encourage a reliance on the verbal code. As predicted, performance in the imagery task was significantly improved by suppression when the stimuli were easy to name (Experiment 1) but was severely disrupted by labeling when the stimuli were difficult to name (Experiment 2). We concluded that verbal recoding of stimuli in short-term memory during learning disrupts the ability to generate veridical mental images from long-term memory.     

Characteristics of implicit chaining in cotton-top tamarins (Saguinus oedipus)

In human cognition there has been considerable interest in observing the conditions under which subjects learn material without explicit instructions to learn. In the present experiments, we adapted this issue to nonhumans by asking what subjects learn in the absence of explicit reinforcement for correct responses. Two experiments examined the acquisition of sequence information by cotton-top tamarins (Saguinus oedipus) when such learning was not demanded by the experimental contingencies. An implicit chaining procedure was used in which visual stimuli were presented serially on a touchscreen. Subjects were required to touch one stimulus to advance to the next stimulus. Stimulus presentations followed a pattern, but learning the pattern was not necessary for reinforcement. In Experiment 1 the chain consisted of five different visual stimuli that were presented in the same order on each trial. Each stimulus could occur at any one of six touchscreen positions. In Experiment 2 the same visual element was presented serially in the same five locations on each trial, thereby allowing a behavioral pattern to be correlated with the visual pattern. In this experiment two new tests, a Wild-Card test and a Running-Start test, were used to assess what was learned in this procedure. Results from both experiments indicated that tamarins acquired more information from an implicit chain than was required by the contingencies of reinforcement. These results contribute to the developing literature on nonhuman analogs of implicit learning.     

When obvious covariations are not even learned implicitly

The present experiments examine the impact of covariation type and attention on implicit covariation learning. Experiments 1 and 2 compare learning of stimulus–stimulus (s–s) and stimulus–response (s–r) covariations. Although stimuli and responses were predicted by a distinct feature of the display, implicit learning neither of s–s nor of s–r covariations was observed. Experiments 3–5 explore the impact of attention on implicit learning of an s–r covariation. Distinct features either of the targets or of an incidental but centrally presented object predicted the responses. Implicit covariation learning was restricted to predictors that were part of to-be-attended targets. Finally, Experiment 6 shows implicit learning of a partial s–r covariation in which only one of two responses is predicted by target features. It is argued that implicit learning is based on the formation of associations between simultaneously activated distinct representations. Because only attended stimuli seem to reach a sufficient level of mental distinctiveness, attending the predictive information most likely is an indispensable prerequisite for implicit covariation learning to occur.     

The subliminal mere exposure effect does not generalize to structurally related stimuli.

R.F. Bornstein (1994) questioned whether subliminal mere exposure effects might generalize to structurally related stimuli, thereby providing evidence for the existence of implicit learning. Two experiments examined this claim using letter string stimuli constructed according to the rules of an artificial grammar. Experiment 1 demonstrated that brief, masked exposure to grammatical strings impaired recognition but failed to produce a mere exposure effect on novel structurally related strings seen at test. Experiment 2 replicated this result but also demonstrated that a reliable mere exposure effect could be obtained, provided the same grammatical strings were presented at test. The results suggest that the structural relationship between training and test items prevents the mere exposure effect when participants are unaware of the exposure status of stimuli, and therefore provide no evidence for the existence of implicit learning.     

Implicit learning of semantic category sequences: response-independent acquisition of abstract sequential regularities

Through the use of a new serial naming task, the authors investigated implicit learning of repeating sequences of abstract semantic categories. Participants named objects (e.g., table, shirt) appearing in random order. Unbeknownst to them, the semantic categories of the objects (e.g., furniture, clothing) followed a repeating sequence. Irrespective of whether participants were instructed to attend to the categories (Experiment 1) or whether no mention was made of the categories (Experiments 2 and 3), naming latencies reliably increased when the repeating category sequence was switched to a random sequence. This was the case even for participants showing no explicit knowledge in reproduction and recognition tests. Results indicate that abstract sequential structures are learned implicitly, even if neither the surface stimuli nor the responses follow a sequence.     

序列位置内隐学习产生机制的实验研究

内隐学习是当今认知和学习领域继内隐记忆之后又一重要的研究课题。该研究利用序列反应时研究程式,通过两个实验,对序列位置内隐学习产生的机制进行了探讨。结果表明：（１）在序列反应时任务程式中,随着反应一刺激间隔的延长,序列位置内隐学习的学习量逐渐减少;（２）异形同模式迁移组和异形异模式迁移组被试间内隐学习量无显著差异,被试未能内隐地习得抽象的序列模式。说明序列位置内隐学习产生的基础是水平联结,在该实验条件下没有发现垂直联结存在的证据。     

Specific sequence effects in the serial reaction time task

The Serial Reaction Time (SRT) task was used in 2 experiments to determine if the specific sequence used by the task influences implicit learning. In Experiment 1, participants performed the SRT task with the locations of the stimuli determined by a commonly used fixed sequence (taken from P. J. Reber & L. R. Squire, 1998), by a fixed sequence that was uniquely generated for each participant, or at random. Experiment 2 used the same basic design, but the random condition was changed so that each possible transition between responses was seen the same number of times, making it more comparable to the fixed-sequence conditions. Results from both experiments indicate that the specific sequence used in the SRT task influences the strength of implicit learning effects. Follow-up analyses show that the strength of implicit learning can be linked to the presence of particular types of triads within the sequence. The authors suggest that future researchers should not use on a single fixed sequence across all participants when using the SRT task but should instead generate different fixed sequences for each participant to enhance the generalizability of their results.     

Striatal activity in concept learning

Striatal learning systems have been implicated in learning relationships between visual stimuli and outcomes. In the present study, the activity of the striatum during visual concept learning in humans was examined by using functional magnetic resonance imaging (fMRI). Participants performed three concept-learning tasks and a baseline task. The participants were trained to criterion before fMRI scanning on two tasks, verbal and implicit. In the verbal task, classification could be performed on the basis of a simple verbal rule, but in the implicit task, there was no simple verbal rule. The novel-implicit learning task, in which an implicit structure was used, was not encountered by the participants before scanning. Across all three concept-learning tasks, there was significant activation in the striatum, in comparison with the baseline task. The striatum was recruited similarly in classification when the participants had different levels of expertise (novel-implicit vs. verbal and implicit) and were able to verbalize their learning to different degrees (verbal vs. implicit and novel-implicit). There was left lateral occipital activation when learning was implicit (implicit and novel-implicit), but not when learning was easily verbalized (verbal).     

The differential role of premotor frontal cortex and basal ganglia in motor sequence learning: evidence from focal basal ganglia lesions

There has been a growing interest in the differential role of various neural structures in implicit learning processes. The goal of our study was to clarify how focal lesions restricted to the basal ganglia interfere with different aspects of implicit visuo-motor sequence learning. A version of the Serial Reaction Time Task (SRTT) of Nissen and Bullemer using a 12-trial sequence was administered. A total of 20 subjects with focal basal ganglia lesions caused by ischemic or hemorrhagic infarction and 20 matched control subjects participated in this study. The results indicate that subjects with focal basal ganglia lesions showed unimpaired implicit learning of a 12-item motor sequence. Subjects with basal ganglia lesions, however, had more difficulties improving their general proficiency with the reaction-time task independent of sequence-specific learning. We observed a tendency toward smaller regional volumes in the cerebellum and left pre-supplementary motor area (pre-SMA) of subjects with basal ganglia lesions. Smaller cerebellar and pre-SMA volumes were related to lower implicit learning performance in the lesion group. The size of lesions in the basal ganglia was not related to sequence-specific implicit learning but had a significant influence on subjects' general proficiency for execution of the reaction-time task. We propose that implicit learning is achieved by a distributed network of cortical and subcortical structures. The basal ganglia seem to be responsible for adjusting to the general requirements of a task rather than for learning specific associations between stimuli that might be accomplished by premotor frontal areas and the cerebellum instead.     

Unconscious symmetrical inferences: A role of consciousness in event integration

Explicit and implicit learning have been attributed to different learning processes that create different types of knowledge structures. Consistent with that claim, our study provides evidence that people integrate stimulus events differently when consciously aware versus unaware of the relationship between the events. In a first, acquisition phase participants sorted words into two categories (A and B), which were fully predicted by task-irrelevant primes-the labels of two other, semantically unrelated categories (C and D). In a second, test phase participants performed a lexical decision task, in which all word stimuli stemmed from the previous prime categories (C and D) and the (now nonpredictive) primes were the labels of the previous target categories (A and B). Reliable priming effects in the second phase demonstrated that bidirectional associations between the respective categories had been formed in the acquisition phase (A<-->C and B<-->D), but these effects were found only in participants that were unaware of the relationship between the categories! We suggest that unconscious, implicit learning of event relationships results in the rather unsophisticated integration (i.e., bidirectional association) of the underlying event representations, whereas explicit learning takes the meaning of the order of the events into account, and thus creates unidirectional associations.     

Social intuition as a form of implicit learning: Sequences of body movements are learned less explicitly than letter sequences

In the current paper, we first evaluate the suitability of traditional serial reaction time (SRT) and artificial grammar learning (AGL) experiments for measuring implicit learning of social signals. We then report the results of a novel sequence learning task which combines aspects of the SRT and AGL paradigms to meet our suggested criteria for how implicit learning experiments can be adapted to increase their relevance to situations of social intuition. The sequences followed standard finite-state grammars. Sequence learning and consciousness of acquired knowledge were compared between 2 groups of 24 participants viewing either sequences of individually presented letters or sequences of body-posture pictures, which were described as series of yoga movements. Participants in both conditions showed above-chance classification accuracy, indicating that sequence learning had occurred in both stimulus conditions. This shows that sequence learning can still be found when learning procedures reflect the characteristics of social intuition. Rule awareness was measured using trial-by-trial evaluation of decision strategy (Dienes & Scott, 2005; Scott & Dienes, 2008). For letters, sequence classification was best on trials where participants reported responding on the basis of explicit rules or memory, indicating some explicit learning in this condition. For body-posture, classification was not above chance on these types of trial, but instead showed a trend to be best on those trials where participants reported that their responses were based on intuition, familiarity, or random choice, suggesting that learning was more implicit. Results therefore indicate that the use of traditional stimuli in research on sequence learning might underestimate the extent to which learning is implicit in domains such as social learning, contributing to ongoing debate about levels of conscious awareness in implicit learning.     

Correlation and response relevance in sequence learning

We tested the effects of introducing a secondary sequence into the serial reaction time task. Specifically, we examined the role of correlated streams of information and response relevance. In the first experiment, the order of stimulus locations was correlated with the order of key press responses in the conventional way. A symbol-identity sequence, of a different length, was also present but no manual responses were made to it, and it was not correlated with any other stream of information. In the second experiment, two concurrent streams of location-based stimuli were presented. Both were sequenced but only one sequence required responses. Importantly, the sequences were either correlated with one another or not (same vs. different lengths). In the third experiment, the same design was used but with one sequence visual and the other auditory. In all three experiments, participants became sensitive to the sequence that required responses, and resultant knowledge was largely explicit. They were also sensitive to the sequence that did not require responses but only when it was correlated with the sequence that did, and here resultant knowledge was implicit. The findings suggest that the presence of a secondary sequence can affect learning, but only when stimuli in that sequence are integrated, through correlation, with responses made to the primary sequence.     

Task integration as a factor in secondary-task effects on sequence learning

In several studies it has been found that implicit sequence learning is impaired by the concurrent performance of a secondary task. In most studies the task was to count high-pitched tones when high-pitched and low-pitched tones were presented in a random sequence. In this paper the hypothesis is examined that dual-task interference in the particular combination of tasks results from task integration, in particular from the learning of an integrated visual-auditory sequence in which every second (auditory) element is random. Instead of the tone-counting task a similar go/no-go task was used in which foot responses to high-pitched tones were performed. In Exp. 1 the sequence of tones was random in one condition, but in two other conditions repeated tone sequences of 5 and 6 elements were combined with visual sequences of 6 elements. Under dual-task test conditions, implicit learning of the visual as well as the auditory sequences was better with the auditory sequence of 6 elements than of 5 elements, while under single-task test conditions the nature of the tone sequence had no effect. In Exp. 2 the superior implicit learning with the 6-element sequence was replicated with different test procedures in which either the visual or auditory sequence was changed to random or in which the two sequences remained intact but were shifted by one element relative to each other. Randomization of the visual or auditory sequences not only impaired visual or auditory RT, respectively, but also impaired RT to stimuli in the other modality, and this cross-modal effect was almost as strong as the intra-modal effect of randomization. Finally, in Exp. 3 it was shown that integrated visual-auditory sequences are learned only when responses to both of them are required, but not when the tones can be neglected. These results are consistent with a conception of implicit learning as (at least partly) a basic and nonselective type of learning of all potentially behaviorally relevant relations between stimuli in the environment and one's own actions.     

中小学生内隐序列学习的机制

内隐序列学习是内隐学习的一种重要形式。该文探讨了中小学生内隐序列学习的心理机制及次级任务影响内隐序列学习的实质。结果表明,中小学生对不同结构序列的内隐学习是由一个单一的学习机制完成的,学习的过程即是形成序列内相邻元素间联合的过程;另外,注意能量并不是内隐序列学习的重要影响因素,次级任务影响内隐序列学习并不是因为其分散了注意能量,而是破坏了对序列元素的组织。     

Are correlated streams of information necessary for implicit sequence learning?

We investigated whether the existence of correlated streams of information is necessary for incidental sequence learning to occur. We ran three separate experiments with a total of 201 undergraduate students. Each experiment had at least one condition with two streams of sequenced information that were correlated. The correlations differed in terms of the kind of responses that were required, the kind of tasks and stimuli, the on-screen locations at which they occurred and how they were combined. Only in conditions with correlated sequences was implicit sequence learning found. Our results suggest that the presence of correlated streams of information may be the main pre-requisite for implicit sequence learning.     

Mood and memory: Mood-congruity effects in absence of mood

Themood-congruity effect refers to facilitated processing of information when the affective valence of this information is congruent with the subject’s mood. In this paper we argue that mood may be a sufficient but not a necessary condition to produce the mood-congruity effect of selective learning. Two experiments are presented in which subjects learned lists of words with neutral, positive, and negative affective valences. In the learning task the subjects were instructed to behave as if they were depressed or happy. The mood-congruity effect was indeed obtained. The effect was stronger with subjects who “predicted” the relationship between mood and affective word valence than with subjects who were unaware of this relationship. The results are not simply attributed to task demands, but are interpreted in terms of a model of cognitive processes and people’s knowledge about mood states.     

Can sequence learning be implicit? New evidence with the process dissociation procedure

Can we learn without awareness? Although this issue has been extensively explored through studies of implicit learning, there is currently no agreement about the extent to which knowledge can be acquired and projected onto performance in an unconscious way. The controversy, like that surrounding implicit memory, seems to be at least in part attributable to unquestioned acceptance of the unrealistic assumption that tasks are process-pure--that is, that a given task exclusively involves either implicit or explicit knowledge. Methods such as the process dissociation procedure (PDP, Jacoby, 1991) have been developed to overcome the conceptual limitations of the process purity assumption but have seldom been used in the context of implicit learning research. In this paper, we show how the PDP can be applied to a free generation task so as to disentangle explicit and implicit sequence learning. Our results indicate that subjects who are denied preparation to the next stimulus nevertheless exhibit knowledge of the sequence through their reaction time performance despite remaining unable (1) to project this knowledge in a recognition task and (2) to refrain from expressing their knowledge when specifically instructed to do so. These findings provide strong evidence that sequence learning can be unconscious.