Qualitative differences between implicit and explicit sequence learning.

Four experiments investigate the differences between implicit and explicit sequence learning concerning their resilience to structural and superficial task changes. A superficial change that embedded the SRT task in the context of a selection task, while maintaining the sequence, did selectively hinder the expression of implicit learning. In contrast, a manipulation that maintained the task surface, but decreased the sequence validity, affected the expression of learning specifically when it was explicit. These results are discussed in the context of a dynamic framework (Cleeremans & Jime'nez, 2002), which assumes that implicit knowledge is specially affected by contextual factors and that, as knowledge becomes explicit, it allows for the development of relevant metaknowledge that modulates the expression of explicit knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Which attention is needed for implicit sequence learning?

The role of attention in implicit sequence teaming was investigated in 3 experiments in which participants were presented with a serial reaction time (SRT) task under single- or dual-task conditions. Unlike previous studies using this paradigm, these experiments included only probabilistic sequences of locations and arranged a counting task performed on the same stimulus on which the SRT task was being carried out. Another sequential contingency was also arranged between the dimension to be counted and the location of the next stimulus. Results indicate that the division of attention barely affected teaming but that selective attention to the predictive dimensions was necessary to learn about the relation between these dimensions and the predicted one. These results are consistent with a theory of implicit sequence teaming that considers this teaming as the result of an automatic associative process running independently of attentional load, but that would associate only those events that are held simultaneously in working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disorganization of microfilaments and intermediate filaments interferes with the assembly and stability of desmosomes in MDCK epithelial cells

Using the serial reaction time (SRT) task developed by Nissen and Bullemer (1987, Cognitive Psychology, 19, 1-32), implicit memory performance was examined in four groups of subjects: nondemented healthy aged individuals; nondemented Parkinson's disease individuals; very mildly demented senile dementia of the Alzheimer type (SDAT) individuals; and mildly demented SDAT individuals. The SRT task involved four blocks of a repeated 10-item keypress sequence that tapped general skill development along with a fifth block of a nonrepeated sequence that presumably reflected the impact of switching from a learned set of associations (developed during the first four blocks) to a novel sequence. The increase in response latency from the fourth repeated block to the fifth nonrepeated block was used as the reflection of implicit learning. The results revealed preserved implicit memory performance in the very mildly demented individuals compared to that of the age-matched control individuals. However, the mildly demented SDAT individuals and the nondemented Parkinson's disease individuals showed reliably less implicit learning, compared to the age-matched control individuals. Differences between the past studies using the SRT task to tap implicit memory performance in SDAT individuals and the present study are discussed in some detail. We conclude that nondemented Parkinson's disease individuals and mildly demented SDAT individuals produce some deficit in the formation of new associations in implicit memory, as measured by the SRT task.     

The neural correlates of implicit sequence learning in schizophrenia.

Twenty-seven schizophrenia spectrum patients and 25 healthy controls performed a probabilistic version of the serial reaction time task (SRT) that included sequence trials embedded within random trials. Patients showed diminished, yet measurable, sequence learning. Postexperimental analyses revealed that a group of patients performed above chance when generating short spans of the sequence. This high-generation group showed SRT learning that was similar in magnitude to that of controls. Their learning was evident from the very 1st block; however, unlike controls, learning did not develop further with continued testing. A subset of 12 patients and 11 controls performed the SRT in conjunction with positron emission tomography. High-generation performance, which corresponded to SRT learning in patients, correlated to activity in the premotor cortex and parahippocampus. These areas have been associated with stimulus-driven visuospatial processing. Taken together, these results suggest that a subset of patients who showed moderate success on the SRT used an explicit stimulus-driven strategy to process the sequential stimuli. This adaptive strategy facilitated sequence learning but may have interfered with conventional implicit learning of the overall stimulus pattern. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parallel response selection disrupts sequence learning under dual-task conditions.

Some studies suggest that dual-task processing impairs sequence learning; others suggest it does not. The reason for this discrepancy remains obscure. It may have to do with the dual-task procedure often used. Many dual-task sequence learning studies pair the serial reaction time (SRT) task with a tone-counting secondary task. The tone-counting task, however, is not ideal for studying the cognitive processes involved in sequence learning. The present experiments sought to identify the nature of the interference responsible for disrupting sequence learning in dual-task situations using more tractable dual-task procedures. Experiments 1 and 2 showed that parallel-interfering central processing disrupts sequence learning. Experiment 3 used a novel combination of the SRT task as the secondary task in a psychological refractory period procedure. It showed that SRT task performance can be disrupted without disrupting sequence learning when that disruption involves a response-selection bottleneck rather than parallel response selection. Together, these results suggest that it is the overlap of central processes involved in successfully performing the 2 tasks concurrently that leads to learning deficits in dual-task sequence learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired Higher Order Implicit Sequence Learning on the Verbal Version of the Serial Reaction Time Task in Patients With Parkinson's Disease.

Although neuroimaging studies have strongly implicated basal ganglia involvement in implicit sequence learning, serial reaction time (SRT) studies with Parkinson's disease (PD) patients have yielded mixed results. The present research sought to examine the ability of people with PD to implicitly learn sequences with different sequential structures and to objectively assess explicit knowledge. A version of the SRT task that reduces motor demands was used to compare 19 patients with PD but not dementia and 37 matched controls. PD patients showed less implicit sequence-specific learning for both sequences and reduced response time improvement over sequential trials for the more complex sequence. A closer examination revealed that the deficit involved higher order sequential associations as well as the learning of pairwise information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ammonia inhibits neural cell adhesion molecule polysialylation in Chinese hamster ovary and small cell lung cancer cells

Contrasts between implicit and explicit knowledge in the serial reaction time (SJRT) paradigm have been challenged because they have depended on a single dissociation; intact implicit knowledge in the absence of corresponding explicit knowledge. In the SRT task, subjects respond with a corresponding keypress to a cue that appears in one of four locations. The cue follows a repeating sequence of locations, and subjects can exhibit knowledge of the repeating sequence through increasingly rapid performance (an implicit test) or by being able to recognize the sequence (an explicit test). In our study, amnesic patients were given extensive SRT training. Their implicit and explicit test performance was compared to the performance of control subjects who memorized the training sequence. Compared with control subjects, amnesic patients exhibited superior performance on the implicit task and impaired performance on the explicit task. This crossover interaction suggests that implicit and explicit knowledge of the embedded sequence are separate and encapsulated and that they presumably depend on different brain systems.     

Is implicit sequence learning impaired in Parkinson's disease? A meta-analysis.

The aim of the present study was to examine impairment of implicit learning in Parkinson's disease (PD) by means of a meta-analysis of studies that used the serial reaction time (SRT) task. The authors performed a systematic review and meta-analysis of published journal articles (1987-2005) that used the SRT task with patients with PD. The principal outcome measures used to compare studies were (a) the difference in reaction time between the last block of ordered sequence trials and the randomized block for PD and control participants and (b) fixed and random effects pooled estimates by the inverse weighting method. Six studies, including 67 patients with PD, met the inclusion criteria. The meta-analysis showed that implicit learning was impaired in PD, relative to healthy controls, with a standardized mean difference of 0.73 (95% confidence interval = 0.38, 1.07). Implicit sequence learning appears to be impaired in patients with PD. Some common methodological weaknesses and limitations in the reporting of statistical data are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit sequence learning and contextual cueing do not compete for central cognitive resources.

Sequence learning and contextual cueing explore different forms of implicit learning, arising from practice with a structured serial task, or with a search task with informative contexts. We assess whether these two learning effects arise simultaneously when both remain implicit. Experiments 1 and 2 confirm that a cueing effect can be observed under a continuous setting and that there is no interference between contextual cueing and sequence learning. Experiments 3a and 3b tested whether an interference arises specifically when the sequence becomes explicit. Results show that the expression of contextual cueing disappeared in those conditions but that context information is still acquired, and it affects performance when the sequence is removed. The results are discussed in relation to the current debates about the automaticity of implicit learning, and about the role of attention in the acquisition and expression of contextual cueing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Indirect Learning of Event Sequences: The Effects of Divided Attention and Stimulus Continuity.

In a serial reaction time (SRT) task, the learning curve is steeper when the stimuli are presented in a repeating sequential manner rather than in random order (Nissen & Bullemer, 1987). This is true even when subjects report being unaware of the presence of the repeating sequence. The present study examines the nature of this learning under conditions designed to reduce attentional resources and to disrupt the continuity of stimuli. In the first three experiments, subjects were trained in the SRT task, with or without the addition of a secondary tone counting task, and with repeating or non-repeating sequences. The results suggest that some sequence learning occurred despite the presence of a secondary task. Experiment 4 examined the extent of sequence learning when the inter-stimulus interval was varied between trials. The overall results suggest that despite reduced attentional allocation and discontinuous stimulus presentation, some sequence learning occurs. This result supports other work suggesting a dissociation between learning when measured explicitly, and when assessed through performance indicators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of attention in implicit learning.

Previous research has shown that implicit learning of a serial pattern in a reaction time (RT) task is eliminated or reduced when the task is performed concurrently with a tone-counting task. These results led to the inference that implicit learning requires attentional capacity. Two experiments tested the alternative hypothesis that the tone-counting task disrupts learning by preventing consistent organization of the sequence. The tone-counting condition was compared with a condition with additional attentional demands, but no disruption of organization, and with a condition with no additional attentional demands, but disruption of organization. The results were consistent with the organizational hypothesis. It is argued that learning depends on practicing consistently organized runs of trials, that shifts of attention may determine how the runs are organized, and that the relation between attention and learning depends more on organization and intention than on capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit learning of new verbal associations.

Implicit learning of a series of new verbal associations was studied in four experiments. The first two experiments demonstrated that learning of a repeating sequence of verbal stimuli may occur without awareness, but only when the stimulus–response mapping requires an attention-demanding activity: Subjects who were unaware of the sequence learned when instructed to categorize the stimuli, but not when instructed simply to read them. However, in both situations, unaware subjects performed no better than untrained control subjects in expressing their knowledge of the sequence explicitly. In Experiments 3 and 4, subjects showed implicit learning when the task involved either motor responses to verbal stimuli or verbal responses to spatially arranged stimuli. These findings are discussed in terms of the conditions under which implicit learning can be obtained. First, they demonstrate implicit learning of a set of new associations in the verbal domain. Second, the data suggest that attention is important in implicit learning. Finally, the degree of interitem organization that is familiar preexperimentally seems to partially determine the amount of implicit learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"What matters in implicit task sequence learning: Perceptual stimulus features, task sets, or correlated streams of information?" Correction to Weiermann et al. (2010).

Reports an error in "What matters in implicit task sequence learning: Perceptual stimulus features, task sets, or correlated streams of information" by Brigitte Weiermann, Josephine Cock and Beat Meier (Journal of Experimental Psychology: Learning, Memory, and Cognition, 2010[Nov], Vol 36[6], 1492-1509). Two figures appearing on pages 1500 and 1502 contained incorrect labels for the x-axis of the control condition (ranran). The correct versions of Figure 3 and Figure 4 are provided in the erratum. (The following abstract of the original article appeared in record 2010-22281-001.) Implicit task sequence learning may be attributed to learning the order of perceptual stimulus features associated with the task sequence, learning a series of automatic task set activations, or learning an integrated sequence that derives from 2 correlated streams of information. In the present study, our purpose was to distinguish among these 3 possibilities. In 4 separate experiments, we replicated and extended a previous study by Heuer, Schmidtke, and Kleinsorge (2001). The presence or absence of a sequence of tasks, as well as that of a sequence of different task-to-response mappings, was manipulated independently within experiments. Evidence of implicit sequence learning was found only when correlated sequences of tasks and mappings were present. No sequence learning effects were found when only a single task sequence or a single mapping sequence was present, even when the structure of the single sequence was identical to the structure of the integrated sequence of task-mapping combinations. These results suggest that implicit task sequence learning is not dependent on either perceptual learning of stimulus features or automatic task-set activation per se. Rather, it appears to be driven by correlated streams of information. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Flexible serial response learning by pigeons (Columba livia) and humans (Homo sapiens).

Experimental tasks designed to involve procedural memory are often rigid and unchanging, despite many reasons to expect that implicit learning processes can be flexible and support considerable variability. A version of the serial response time (SRT) task was developed, in which the locations of targets were probabilistically determined. Targets appeared in locations according to both a structured sequence and a cue validity parameter, and the time to respond to each target was measured. Pigeons (Columba livia) and humans (Homo sapiens) both showed response time facilitation at the highest tested value for cue validity, and the magnitude of that facilitation gradually weakened as cue validity was decreased. Both species showed evidence that response times were largely determined by the local predictabilities of individual cue locations. In addition, humans showed some evidence that explicit knowledge of the sequence affected response times, specifically when cue validity was 100%. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

What matters in implicit task sequence learning: Perceptual stimulus features, task sets, or correlated streams of information?

[Correction Notice: An erratum for this article was reported in Vol 37(4) of Journal of Experimental Psychology: Learning, Memory, and Cognition (see record 2011-13273-005). Two figures appearing on pages 1500 and 1502 contained incorrect labels for the x-axis of the control condition (ranran). The correct versions of Figure 3 and Figure 4 are provided in the erratum.] Implicit task sequence learning may be attributed to learning the order of perceptual stimulus features associated with the task sequence, learning a series of automatic task set activations, or learning an integrated sequence that derives from 2 correlated streams of information. In the present study, our purpose was to distinguish among these 3 possibilities. In 4 separate experiments, we replicated and extended a previous study by Heuer, Schmidtke, and Kleinsorge (2001). The presence or absence of a sequence of tasks, as well as that of a sequence of different task-to-response mappings, was manipulated independently within experiments. Evidence of implicit sequence learning was found only when correlated sequences of tasks and mappings were present. No sequence learning effects were found when only a single task sequence or a single mapping sequence was present, even when the structure of the single sequence was identical to the structure of the integrated sequence of task-mapping combinations. These results suggest that implicit task sequence learning is not dependent on either perceptual learning of stimulus features or automatic task-set activation per se. Rather, it appears to be driven by correlated streams of information. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Irrelevant response effects improve serial learning in serial reaction time tasks.

Tones were introduced into a serial reaction time (SRT) task to serve as redundant response effects. Experiment 1 showed that the tones improved serial learning with a 10-element stimulus sequence, but only if the tone effects were mapped onto the responses contingently. Experiment 2 demonstrated that switching to noncontingent response-effect mapping increased SRT only when participants had previously adapted to contingent response-effect mapping. In Experiment 3, the beneficial influence of contingent tone effects on serial learning occurred only when there was sufficient time between the response effects and the next imperative stimuli. The results are discussed in terms of the ideomotor principle. It is claimed that an internal representation of the to-be-produced tone effects develops and gains control over the execution of the response sequence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit learning of a nonverbal sequence in younger and older adults.

Two experiments examined age-related differences in implicit serial learning using the M. J. Nissen and P. Bullemer (see record 1987-13436-001) task. Younger adults and 2 samples of older adults who differed in educational attainment, occupational status, and verbal ability were given a 10-trial repeating sequence embedded in 100-trial blocks. On each trial, participants pressed a key that matched a designated spatial location. Implicit learning was inferred from the difference in reaction time (RT) between a random sequence trial block and the immediately preceding block with the repeating sequence. Results indicated that negative transfer effects were comparable for the younger and higher ability older adults, but lower ability older adults showed less evidence of implicit learning. On an explicit task, younger and higher ability older adults were more accurate than the lower ability older adults. The implications of these findings for current views on implicit learning in adulthood are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial attention and implicit sequence learning: Evidence for independent learning of spatial and nonspatial sequences.

This research investigated whether regular spatial orienting sequences can be learned implicitly and independently of response requirements. In a new version of a serial response task introduced by M. J. Nissen and P. Bullemer (1987) participants had to discriminate between objects that could occur at different locations. Independent sequences determined the succession of locations and objects. Even participants who were not aware of any regularities exhibited evidence for learning of both sequences (Experiment 1). Experiment 2 showed that the joint learning of spatial and object sequences was as efficient as learning of single sequences and that it even occurred when learning required memory for past sequence elements and attention was blocked through a secondary tone-counting task. Results are consistent with the idea that independent systems may exist for the implicit acquisition of spatial and nonspatial regularities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bupropion improves attention but does not affect impulsive behavior in healthy young adults.

Bupropion is an effective abstinence aid for cessation of smoking and possibly other drug use as well. There is evidence that bupropion improves attention and impulse control in certain patient populations, and improvements in these processes could mediate its efficacy as an abstinence aid. In the present study, we tested the effects of acute bupropion on measures of attention and impulsivity in healthy adults with d-amphetamine included as a positive control. Twenty-two nonsmokers (11 women) and 11 smokers (4 women) completed four 4-hr sessions where they received placebo, bupropion (150 or 300 mg), or d-amphetamine (20 mg) in capsules. Ninety minutes after capsule administration, participants were tested on attention with a simple reaction time task (SRT) and on impulsivity with the stop task, a delay and probability discounting task (DPD), and the balloon analogue risk task (BART). Participants also completed mood questionnaires during sessions. Bupropion (150 mg) decreased lapses in attention on the SRT, but did not affect performance on the stop task, DPD, or BART. Amphetamine decreased lapses in attention and speeded sensory motor processing time on the SRT but did not significantly affect responding on the stop task or DPD. On the BART, d-amphetamine tended to decrease risk taking in men but increased risk taking in women. Bupropion (300 mg) and d-amphetamine increased ratings of arousal. These results suggest that bupropion improves attention without affecting impulsive behavior in healthy adults. Improvements in attention may contribute to the effectiveness of bupropion as a pharmacotherapy for smoking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pure perceptual-based sequence learning.

Learning a sequence of target locations when the sequence is uncorrelated with a sequence of responses and target location is not the response dimension (pure perceptual-based sequence learning) was examined. Using probabilistic sequences of target locations, the author shows that such learning can be implicit, is unaffected by distance between target locations, and is mostly limited to first-order transition probabilities. Moreover, the mechanism underlying learning affords processing of information at anticipated target locations and appears to be attention based. Implications for hypotheses of implicit sequence learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)