Comparison of implicit and explicit learning processes in a probabilistic task

This experiment compared the performance with explicit (rule-application and rule-discovery) and implicit (nonrule-instructed) learning approaches on the performance of a probabilistic video game task requiring fine motor control. The task required visual tracking of a small ball of light and "catching" it by means of joystick manipulation. A general pattern of improvement with practice occurred for all conditions. All conditions showed use of predictive relations among stimulus events. However, task performance of the rule-application and rule-discovery conditions were inferior to the nonrule-instructed implicit condition, particularly during the early phases of rule acquisition and application. This pattern strongly suggests substantial performance costs associated with attempting to discover or apply probabilistic rules. Decrements are likely due to increased cognitive demands associated with attempting to remember and strategically apply provided probability rules or attempting to discover and apply potentially important and useful probability information from a complex visual display.     

Chunking in task sequences modulates task inhibition

In a study of the formation of representations of task sequences and its influence on task inhibition, participants first performed tasks in a predictable sequence (e.g., ABACBC) and then performed the tasks in a random sequence. Half of the participants were explicitly instructed about the predictable sequence, whereas the other participants did not receive these instructions. Task-sequence learning was inferred from shorter reaction times (RTs) in predictable relative to random sequences. Persisting inhibition of competing tasks was indicated by increased RTs in n- 2 task repetitions (e.g., ABA) compared with n- 2 nonrepetitions (e.g., CBA). The results show task-sequence learning for both groups. However, task inhibition was reduced in predictable relative to random sequences among instructed-learning participants who formed an explicit representation of the task sequence, whereas sequence learning and task inhibition were independent in the noninstructed group. We hypothesize that the explicit instructions led to chunking of the task sequence, and that n- 2 repetitions served as chunk points (ABA-CBC), so that within-chunk facilitation modulated the inhibition effect.     

When it does hurt to try: adult age differences in the effects of instructions on implicit pattern learning

Trying to learn sometimes impairs implicit learning of artificial grammars and of control systems. We asked whether such negative effects of trying also occur in implicit learning of subtle sequential regularities and whether such effects vary with adult age. Young (n=12, age=20–23) and older (n=24, age=60–80) adults completed an alternating serial response time task in which predictable pattern events alternated with random ones in a visual/spatial display. Half of the participants were informed about the pattern and were instructed to try to discover it (intentional instructions), and half were not (incidental instructions). Age-related deficits in implicit learning occurred for both conditions. In addition, for the older group, but not for the younger one, intentional instructions impaired implicit pattern learning. This negative effect of trying to learn demonstrates another similarity among implicit learning tasks, supporting the view that some common processes underlie different forms of implicit learning.     

Explicit and implicit motor sequence learning in children and adults; the role of age and visual working memory

This study investigated explicit and implicit motor learning, and the influence of visual working memory (VWM) and age. Sixty children and 28 adults learned a nine-button sequence task explicitly and implicitly. Performance in explicit and implicit learning improved with age. Learning curves were similar across ages for implicit learning. In explicit learning, learning curves differed across ages: younger children started slower, but their learning rate was higher compared to older children. Learning curves were similar across VWM scores, but performance in explicit learning was positively influenced by VWM scores. Further research and implications for education and rehabilitation are discussed.     

Categorical implicit learning in real-world scenes: evidence from contextual cueing

The present study examined the extent to which learning mechanisms are deployed on semantic-categorical regularities during a visual searching within real-world scenes. The contextual cueing paradigm was used with photographs of indoor scenes in which the semantic category did or did not predict the target position on the screen. No evidence of a facilitation effect was observed in the predictive condition compared to the nonpredictive condition when participants were merely instructed to search for a target T or L (Experiment 1). However, a rapid contextual cueing effect occurred when each display containing the search target was preceded by a preview of the scene on which participants had to make a decision regarding the scene's category (Experiment 2). A follow-up explicit memory task indicated that this benefit resulted from implicit learning. Similar implicit contextual cueing effects were also obtained when the scene to categorize was different from the subsequent search scene (Experiment 3) and when a mere preview of the search scene preceded the visual searching (Experiment 4). These results suggested that if enhancing the processing of the scene was required with the present material, such implicit semantic learning can nevertheless take place when the category is task irrelevant.     

Implicit and explicit learning: individual differences and IQ

We explored the degree to which individual differences in performance were observed in a group of subjects who worked with two different tasks: one implicit and one explicit. The implicit task was a standard artificial grammar-learning task; the explicit was a series-completion problem-solving task. Substantial individual differences were found between subjects on the explicit task; relatively small individual differences were found on the implicit task. Moreover, performance on the explicit task correlated strongly with intelligence quotient, but performance on the implicit task did not. Data from previous experiments were also found to be in agreement with these results. The findings are presented in the context of a general theory of implicit learning proposed recently by Reber (1989a, in press) that derives from considerations of the evolution of cognitive processes. This evolutionary model argues that unconscious, implicit induction systems are evolutionarily older and antedate conscious, explicit learning processes, and that this antiquity carries with it particular patterns of function that differentiate implicit processes from explicit processes.     

Perceptual training methods compared: the relative efficacy of different approaches to enhancing sport-specific anticipation

The comparative efficacy of different perceptual training approaches for the improvement of anticipation was examined using a goalkeeping task from European handball that required the rapid prediction of shot direction. Novice participants (N = 60) were assigned equally to four different training groups and two different control groups (a placebo group and a group who undertook no training). The training groups received either (i) explicit rules to guide anticipation; (ii) direction as to the location of the key anticipatory cues provided either just verbally (verbal cueing) or supplemented with color highlighting (color cueing); or (iii) undertook a matching judgment task to encourage implicit learning. Performance of the groups was compared on an anticipation test administered before training, after the training intervention, under a condition involving evaluative stress, and after a 5-month retention period. The explicit learning, verbal cueing, and implicit learning conditions provided the greatest sustained improvements in performance whereas the group given color cueing performed no better than the control groups. Only the implicit learning group showed performance superior to the control groups under the stress situation. The verbal cueing, color cueing, and implicit learning groups formulated the lowest number of explicit rules related to the critical shoulder cue although the reported use of general cues and rules based on all cues did not differ between any of the groups. Anticipation can be improved through a variety of different perceptual training approaches with the relative efficacy of the different approaches being contingent upon both the time scale and conditions under which learning is assessed.     

Learning from implicit learning literature: Comment on Shea, Wulf, Whitacre, and Park (2001)

In their analysis of complex motor skill learning, Shea, Wulf, Whitacre, and Park (2001) have overlooked one of the most robust conclusions of the experimental studies on implicit learning conducted during the last decade--namely that participants usually learn things that are different from those that the experimenter expected them to learn. Weshow that the available literature on implicit learning strongly suggests that the improved performance in Shea et al.'s Experiments 1 and 2 (and similar earlier experiments, e.g., Wulf & Schmidt, 1997) was due to the exploitation of regularities in the target pattern different from those on which the postexperimental interview focused. This rules out the conclusions drawn from the failure of this interview to reveal any explicit knowledge about the task structure on the part of the participants. Similarly, because the information about the task structure provided to an instructed group of participants in Shea et al.'s Experiment 2 did not concern the regularities presumably exploited by the standard, so-called implicit, group, Shea et al.'s claim that explicit knowledge may be less effective than implicit knowledge is misleading.     

Performing the unexplainable: Implicit task performance reveals individually reliable sequence learning without explicit knowledge

Memory-impaired patients express intact implicit perceptual-motor sequence learning, but it has been difficult to obtain a similarly clear dissociation in healthy participants. When explicit memory is intact, participants acquire some explicit knowledge and performance improvements from implicit learning may be subtle. Therefore, it is difficult to determine whether performance exceeds what could be expected on the basis of the concomitant explicit knowledge. Using a challenging new sequence-learning task, robust implicit learning was found in healthy participants with virtually no associated explicit knowledge. Participants trained on a repeating sequence that was selected randomly from a set of five. On a performance test of all five sequences, performance was best on the trained sequence, and two-thirds of the participants exhibited individually reliable improvement (by chi-square analysis). Participants could not reliably indicate which sequence had been trained by either recognition or recall. Only by expressing their knowledge via performance were participants able to indicate which sequence they had learned.     

Secondary-task effects on classification learning

Probabilistic classification learning can be supported by implicit knowledge of cue-response associations. We investigated whether forming these associations depends on attention by assessing the effect of performing a secondary task on learning in the probabilistic classification task (PCT). Experiment I showed that concurrent task performance significantly interfered with performance of the PCT. Experiment 2 showed that this interference did not prevent learning from occurring. On the other hand, the secondary task did disrupt acquisition of explicit knowledge about cue-outcome associations. These results show that concurrent task performance can have different effects on implicit and explicit knowledge acquired within the same task and also underscore the importance of considering effects on learning and performance separately.     

认知疲劳效应对内隐记忆与外显记忆的影响

本研究通过比较内隐记忆与外显记忆受到认知疲劳影响的情况,以了解内隐记忆的自动化加工机制。实验采用被试内设计,使用词汇判断与词汇再认任务测量内隐记忆与外显记忆。实验结果发现,相对于控制组,疲劳组的被试在完成疲劳任务后内隐记忆成绩显著下降,而外显记忆没有受到影响。结果说明相对于外显记忆,内隐记忆更容易受到认知疲劳影响。内隐记忆虽然是无意识的认知加工,但是与其他自动化加工具有不同的特征。     

认知疲劳效应对内隐记忆与外显记忆的影响

本研究通过比较内隐记忆与外显记忆受到认知疲劳影响的情况,以了解内隐记忆的自动化加工机制。实验采用被试内设计,使用词汇判断与词汇再认任务测量内隐记忆与外显记忆。实验结果发现,相对于控制组,疲劳组的被试在完成疲劳任务后内隐记忆成绩显著下降,而外显记忆没有受到影响。结果说明相对于外显记忆,内隐记忆更容易受到认知疲劳影响。内隐记忆虽然是无意识的认知加工,但是与其他自动化加工具有不同的特征。     

学优生与学困生内隐与外显协同学习的比较研究

根据目前国内采用的标准,选取学优生和学困生各120人。运用内隐学习中的双条件人工语法材料和强分离的实验范式,考察和比较了两种学生的内隐学习、内隐与外显协同学习的成绩。结果显示:(1)学优生在外显学习、协同学习(先内隐后外显以及内隐与外显交替)方式下的成绩显著好于学困生,而在内隐学习方式下,二者成绩差异不显著。(2)学优生的外显学习及协同学习成绩显著好于内隐学习成绩,而学困生在四种学习方式下成绩差异不显著。表明在人工语法学习中学优生的有意识学习及其与无意识的协同学习效果较好,而学困生的有意识学习及协同学习较差。     

Implicit learning: Robustness in the face of psychiatric disorders

The performance of a group of psychiatric inpatients on two different cognitive tasks was compared with that of a control group of college undergraduates. The task in the first experiment was implicit learning of a complex, synthetic grammar; the task in the second experiment was explicit learning of relatively simple letter-to-number matching rules. In the first experiment, differences between the normals and the psychiatrically impaired were found on the preliminary memorization task but not on the implicit grammar learning task; in the second experiment, differences were observed on all phases of the experiment, with the inpatients performing no better than chance. These findings provide support for the hypothesis that, under appropriate conditions, individuals suffering from serious disorders may show no deficits when working with complex and abstract stimulus domains while showing serious performance problems when working with relatively simple, concrete stimuli. The key factor is that the former were presented as tasks that tap nonreflective, implicit processes, whereas the latter were put forward as ones that recruit conscious, explicit processes.The experiments are based in part on studies reported in Abrams (1987). Preparation of this article was supported in part by a grant from the City University of New York PSC-CUNY Research Award Program, Brooklyn College of CUNY.     

Influence of body-centered information on the transfer of spatial learning from a virtual to a real environment

This study investigated the effects of body-centred information on the transfer of spatial learning using a wayfinding task and tasks that specifically probe the route and survey strategies of navigation. The subject learned a route in either a real or a virtual environment (VE; 3D scale model of a Bordeaux neighbourhood) and then reproduced it in the real environment. The involvement of body-based information was manipulated across the spatial learning conditions in the VE: participants learned with full body-based information (treadmill with rotation), with the translational component only (treadmill without rotation) or without body-based information (joystick). In the wayfinding task, the results showed a significant effect of the learning environment with the best scores obtained in the real and treadmill with rotation conditions. There was no significant difference between these two conditions, but the real condition was significantly different from the treadmill without rotation and joystick conditions. Also, the visual flow was sufficient to successfully perform the two egocentric tasks used as well as a direction estimation task (a survey task), in so far as there is no significant difference between the joystick and the treadmill conditions. By contrast, the distance estimates were improved by the treadmill condition including the translational component (but not the rotational component). Finally, our results show that treadmill with rotation promotes the transfer of spatial learning from a virtual to a real environment (compared to joystick and treadmill without rotation). Moreover, body-centred informations are more involved in allocentric (distance estimates) than egocentric navigational strategies.     

The implicit benefit of learning without errors

Two studies examined whether the number of errors made in learning a motor skill, golf putting, differentially influences the adoption of a selective (explicit) or unselective (implicit) learning mode. Errorful learners were expected to adopt an explicit, hypothesis-testing strategy to correct errors during learning, thereby accruing a pool of verbalizable rules and exhibiting performance breakdown under dual-task conditions, characteristic of a selective mode of learning. Reducing errors during learning was predicted to minimize the involvement of explicit hypothesis testing leading to the adoption of an unselective mode of learning, distinguished by few verbalizable rules and robust performance under secondary task loading. Both studies supported these predictions. The golf putting performance of errorless learners in both studies was unaffected by the imposition of a secondary task load, whereas the performance of errorful learners deteriorated. Reducing errors during learning limited the number of error-correcting hypotheses tested by the learner, thereby reducing the contribution of explicit processing to skill acquisition. It was concluded that the reduction of errors during learning encourages the use of implicit, unselective learning processes, which confer insusceptibility to performance breakdown under distraction.     

Statistical Learning Is Not Affected by a Prior Bout of Physical Exercise

This study examined the effect of a prior bout of exercise on implicit cognition. Specifically, we examined whether a prior bout of moderate intensity exercise affected performance on a statistical learning task in healthy adults. A total of 42 participants were allocated to one of three conditions—a control group, a group that exercised for 15 min prior to the statistical learning task, and a group that exercised for 30 min prior to the statistical learning task. The participants in the exercise groups cycled at 60% of their respective O₂max. Each group demonstrated significant statistical learning, with similar levels of learning among the three groups. Contrary to previous research that has shown that a prior bout of exercise can affect performance on explicit cognitive tasks, the results of the current study suggest that the physiological stress induced by moderate‐intensity exercise does not affect implicit cognition as measured by statistical learning.     

Using immediate memory span

To avoid some conceptual and methodological pitfalls found in traditional artificial grammar learning tasks, we developed a new method of measuring implicit learning using immediate memory span. Subjects were presented with sequences generated by an artificial grammar and were asked to reproduce the patterns by pressing buttons on a response box. After exposure to these sequences, subjects showed selective improvement in immediate memory span for novel sequences governed by the same grammar. Individual differences in implicit learning covaried with measures of auditory digit span. Subjects with greater immediate memory processing capacity were better able to learn and subsequently exploit the information available in grammatical sequences. Our results are consistent with a detailed episodic coding framework in which implicit learning occurs as an incidental by-product of explicit task performance. Although subjects encode highly detailed information about specific instances, they use different aspects of this information to accomplish different task-specific demands.     

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.     

Role of the striatum and the cerebellum in motor skill acquisition

Motor skill acquisition was investigated in patients with Parkinson's disease (PD) or cerebellar dysfunction using two sensory-guided tracking tasks. The subjects had to learn to track a visual target (a square) on a computer screen by moving a joystick under two different conditions. In the unreversed task, the horizontal target movements were semi-predictable and could be anticipated. In the reversed task, the horizontal movements of a pointer which had to be kept within the target square were mirror-reversed to the joystick movements. PD patients showed intact learning of the semi-predictable task and reduced learning of the mirror-reversed task; patients with cerebellar dysfunction showed the opposite pattern. These findings are discussed in relation to the differential contribution of the cerebellum and the striatum to motor skill acquisition: the cerebellum appears to participate in the implementation of anticipatory movements, whereas the striatum may be critically involved in types of motor learning which require a high degree of internal elaboration.