The learning of two similar complex movement sequences: does practice insulate a sequence from interference?

Panzer et al. [Panzer, S., Wilde, H., & Shea, C. H. (2006). The learning of two similar complex movement sequences: Proactive and retroactive effects on learning. Journal of Motor Behavior, 38, 60-70] found evidence to indicate that the memory state(s) underpinning the production of a movement sequence that was practiced for one day was essentially "overwritten" when another similar sequence was subsequently practiced on the next day. An interference paradigm was used to determine if additional practice on the first sequence would insulate it from retroactive interference arising from learning a new similar sequence. Participants produced the sequences by moving a lever with their right arm/hand to sequentially presented target locations. The experimental group practiced one 16-element movement sequence (S1) for two consecutive days. A second 16-element sequence (S2) was practiced on Day 3. The sequence practiced on Day 3 was created by switching the positions of 2 of 16 elements in the sequence practiced on the first day. Control groups received either two days of practice on S1 or one day of practice on S2. Contrary to our earlier findings (Panzer, Wilde, & Shea, 2006) of strong retroactive interference when S1 was only practiced for one day, we found no evidence of retroactive interference when S1 was practiced for two days prior to the switch to S2 practice. Interestingly, but also contrary to our earlier findings, we found the learning of S2 was facilitated by the prior practice of S1. This proactive facilitation was observed in S2 acquisition and on the S2 retention test.     

Effector dependent sequence learning in the serial RT task

At least five earlier studies could not find effector-dependent learning in the keying version of the serial reaction time (RT) task. Experiment 1 examined whether effector-dependent learning occurs when participants practice the serial RT task with three fingers of one hand for about 1,300 sequence repetitions instead of the more common 50-100 repetitions. The results confirm that, following extended practice, sequence learning produces an effector-dependent component. Specifically, an unpracticed hand executed a practiced sequence slower than a practiced hand. However, Experiment 2 showed that effector-dependent sequence learning develops only when fingers of one hand are used, suggesting that effector-dependent sequence learning involves adjustment to the mechanical interactions between the fingers of one hand. In addition, when sequences had been practiced with one hand, mirror versions of the practiced sequences in both experiments showed moderate transfer. But when practiced with two hands no transfer to a mirrored version of the sequence was observed. This suggests that only practice with one hand produces a representation that facilitates the execution of mirror sequences. Generally, the same results were found in more or less aware participants, congruent with the idea that the effector-dependent representation and the representation allowing transfer to mirror sequences are implicit.     

Learning of similar complex movement sequences: proactive and retroactive effects on learning

The authors used an interference paradigm to determine the extent to which the learning of 2 similar movement sequences influences the learning of each other. Participants (N=30) produced the sequences by moving a lever with their right arm and hand to sequentially presented target locations. They practiced 2 similar 16-element movement sequences (S1 and S2), 1 sequence on each of 2 consecutive days of practice. Control groups received only 1 day of practice on 1 of the sequences. Early in S2 practice, the experimental group demonstrated a relatively strong level of proactive facilitation arising from previous practice with S1. The advantage was not evident at the end of S2 practice or on the S2 retention test. No advantage of practicing the 1st sequence on the learning of the 2nd sequence (proactive effect) was found in the analysis of element duration in the retention and transfer tests, even though 14 of the 16 elements were common to both sequences. A strong retroactive interference on the switched elements was detected, however. Thus, the memories underpinning S1 seemed to be "overwritten" or adapted in response to the learning of S2.     

Cue competition effects in human causal learning

Five experiments involving human causal learning were conducted to compare the cue competition effects known as blocking and unovershadowing, in proactive and retroactive instantiations. Experiment 1 demonstrated reliable proactive blocking and unovershadowing but only retroactive unovershadowing. Experiment 2 replicated the same pattern and showed that the retroactive unovershadowing that was observed was interfered with by a secondary memory task that had no demonstrable effect on either proactive unovershadowing or blocking. Experiments 3a, 3b, and 3c demonstrated that retroactive unovershadowing was accompanied by an inflated memory effect not accompanying proactive unovershadowing. The differential pattern of proactive versus retroactive cue competition effects is discussed in relationship to amenable associative and inferential processing possibilities.     

The role of horizontal categorization in retroactive and proactive interference

Four paired-associate experiments with a total N of 291 participants investigated the effects of horizontal categorization on retroactive and proactive interference. (Exclusively) horizontal categorization means that unique categorical relationships hold across the A-B and A-C stimulus-response pairs of successive word lists (e.g., fruit--pear, river--Thames, in list 1; and fruit--plum, river--Wolga, in list 2). Experiment 1 found no significant amounts of interference with this type of list organization. However, strong interference arose with the same materials when the categorical structure was destroyed in Experiment 2. A third experiment contrasted two alternative explanations for these results, and Experiment 4 replicated the effect of horizontal categorization (vs. no categorical relationship) in a within-participants design. The results of the four experiments largely fit with a response competition explanation proposed by Bower, Thompson-Schill, and Tulving (1994), adapted to the within-participants designs used here. Overall, the present findings add to a body of evidence demonstrating limits to retroactive and proactive interference.     

Representations underlying skill in the discrete sequence production task: effect of hand used and hand position

Various studies suggest that movement sequences are initially learned predominantly in effector-independent spatial coordinates and only after extended practice in effector-dependent coordinates. The present study examined this notion for the discrete sequence production (DSP) task by manipulating the hand used and the position of the hand relative to the body. During sequence learning in Experiment 1, in which sequences were executed by reacting to key-specific cues, hand position appeared important for execution with the practiced but not with the unpracticed hand. In Experiment 2 entire sequences were executed by reacting to one cue. This produced similar results as in Experiment 1. These experiments support the notion that robustness of sequencing skill is based on several codes, one being a representation that is both effector and position dependent.     

Combined effect of context change and retention interval on interference in causality judgments

Four experiments studied the effects of context change and retention interval on retroactive interference in human causal learning. Experiment 1 found evidence of retroactive interference. Experiment 2 found that either a 48-hr retention interval or a change in the context after the interference treatment decreased retroactive interference. An interaction between context change and retention interval effects was also found, eclipsing the context change effect after the 48-hr retention interval. Experiments 3 and 4 found additivity between context change and retention interval effects when participants were remained of the difference between physical contexts before the test, independently of whether the context change involved a return to the original acquisition context. These results add to the evidence suggesting that spontaneous forgetting is caused by a change in either the physical or the temporal contexts where information is acquired.     

Retroactive interference and mental practice effects on motor performance: a pilot study

This study examined the effect of similar versus dissimilar retroactive interference on the mental practice effects for performing a novel motor skill. Research has shown that mental practice of a motor task can interfere with learning and performance of the task; however, little is known about how different retroactive interference activities affect mental practice effects. 90 volunteers ages 18 to 51 years (M=26.8, SD=9.6) completed a pre-test and post-test of 10 sets of five trials of a throwing task with the non-preferred hand. In the practice phase, participants mentally practiced the throwing task and then mentally practiced a task that was similar, dissimilar, or completed an unrelated reading task. Performance for all groups improved from pre- to post-test; however, there were no differences in increases for the three groups. The findings suggest that mental practice of similar and dissimilar tasks produced no significant interference in performance.     

How motor practice shapes memory: retrieval but not extra study can cause forgetting

We investigated the retrieval specificity of retrieval-induced forgetting (RIF) of motor sequences. In two experiments, participants learned sequential finger movements, each consisting of the movement of two fingers of either the left or the right hand. In the learning phase, these motor sequences were graphically presented and were to be learned as responses to simultaneously presented letter stimuli. Subsequently, participants selectively practiced half the items of one hand. A final recall test then assessed memory for all initially learned items. We contrasted different kinds of selective practice with each other. Whereas retrieval practice required retrieving motor sequences in response to letter stimuli from the learning phase, extra study was an extension of the learning phase, that is, participants performed motor sequences in response to the same animation graphic display as in the learning phase again accompanied by the letter stimulus. All practice conditions strengthened the practiced items, but only retrieval practice resulted in RIF. Thus, the strengthening of items through practice did not suffice to induce forgetting of related motor sequences. Retrieval was a necessary component for practice to shape memory for body movements by impairing the subsequent recall of motor sequences that were related to the practiced motor sequences.     

Time and order effects on causal learning

Five experiments were conducted to explore trial order and retention interval effects upon causal predictive judgments. Experiment 1 found that participants show a strong effect of trial order when a stimulus was sequentially paired with two different outcomes compared to a condition where both outcomes were presented intermixed. Experiment 2 found that a 48-h retention interval eliminates the trial order effect, so that participants gave a global judgment about the relationship between the stimulus and the two outcomes equivalent to the one given by participants that received the two phases intermixed. This result was replicated in Experiment 3 in a situation in which the probability of the outcome in the presence of the cue was changed from .5 for both outcomes (Experiments 1, 2, 4, and 5) to .75 and .25 for outcomes 1 and 2, respectively. Experiment 4 found that retention intervals ranging from 45 min to 48 h eliminated the trial order effect similarly. Experiment 5 found that a 10-min retention interval replicated the effect of time upon sequential training found in precedent experiments, regardless of whether participants remained within the laboratory during the retention interval or spent it outside. The combined results of this experimental series suggest that retention intervals reduce retroactive interference in causal learning by allowing participants to use all the information presented across phases, rather than differentially increasing or decreasing retrieval of information about each of them.     

Asymmetric interference in implicit memory: effects of study-test awareness and stimulus order

This study examined the extent to which fragment completion performance is susceptible to the effects of two different forms of interference (proactive and retroactive) and whether any of these effects depend on participants' awareness of the relationship between study and test. Unaware participants were found to be susceptible to proactive but not retroactive interference. Aware participants did not show evidence of susceptibility to either form of interference. These results contribute to the debate about whether implicit memory is immune to interference effects by demarcating the limits of such an immunity.     

Revisiting an old issue: Retroactive interference as a function of the degree of original and interpolated learning

Prior research has generally shown that the greater the degree of original learning of a list, the greater the amount of retroactive interference that list suffers. In addition, greater learning of interpolated lists produces more retroactive interference. However, in prior research, the degree of learning has typically been confounded with the amount of retrieval practice on the list. Two free-recall experiments are reported in which subjects studied one original list and then 0, 1, 2, 3, or 4 interpolated lists. The degree of original and of interpolated learning was manipulated by varying exposure time. In Experiment 1, where the typical confounding of retrieval practice and degree of interpolated learning was present, greater interpolated learning induced greater retroactive interference, which is consistent with prior research. However, in Experiment 2, where the degree of interpolated learning was manipulated without concomitant variation in retrieval practice, retroactive interference was the same, whether the interpolated lists had been learned well or poorly. Therefore, greater interpolated learning does not increase the amount of retroactive interference. The results also show that the amount of retroactive interference does not depend on the degree of original learning, in agreement with other work on normal forgetting.     

Consistent and Variable Practice Conditions: Effects on Relative and Absolute Timing

The authors conducted the present experiments to resolve the discrepancy between studies in which relative-timing learning has been found to be enhanced by consistent practice conditions and contextual interference experiments in which relative-timing learning has been found to be enhanced more by random practice than by blocked practice. There were 40 participants in Experiment 1 and 48 in Experiment 2. The results of Experiment 1 extended previous findings: The learning of the relative-timing pattern was systematically enhanced by the degree to which the practice conditions promoted movement consistency (constant > blocked > serial > random). Experiment 2 provided evidence that the discrepancy between the relative-timing effects in the 2 groups of studies was a product of the way in which relative-timing goals and feedback were presented. When the feedback was presented as segment times, random practice resulted in generally more stable relative-timing patterns during acquisition than blocked practice did. Thus, in both experiments, the learning of the relative-timing pattern was enhanced by more stable relative-timing conditions during acquisition. Absolute-timing learning, as indexed by the transfer tests, was enhanced by serial or random practice as compared with constant or blocked practice, and was relatively unaffected by feedback conditions directed at the relative-timing pattern. In terms of motor programming theory, those findings are taken as additional evidence for the disassociation of memories supporting generalized motor program (GMP) performance, as indexed by relative timing, and parameter performance, as indexed by absolute timing.     

Retroactive and proactive interference effects in dual learning of blissymbolics and manual sign

Nonspeech systems can be either aided or unaided. Each system possesses its unique learning and memory characteristics. One instructional strategy designed to give learners the advantages of both systems is dual instruction in aided and unaided communication. One problem with this approach, however, might be that of retroactive and proactive interference in learning and memory. The current experiment investigated whether dual instruction in Blissymbolics and manual (ASL) sign would lead to retroactive and proactive interference. Lists of sign/symbol referents in the two systems were taught, to nonhandicapped adults in a controlled setting. No effects of retroactive or proactive interference were found. Additionally, a proactive facilitation effect was found for immediate retention. Results are discussed in terms of the nature of the task, the learning memory attributes of the nonspeech systems, and the effects of sign/symbol translucency.     

Operating characteristics of the implicit learning system supporting serial interception sequence learning

The memory system that supports implicit perceptual-motor sequence learning relies on brain regions that operate separately from the explicit, medial temporal lobe memory system. The implicit learning system therefore likely has distinct operating characteristics and information processing constraints. To attempt to identify the limits of the implicit sequence learning mechanism, participants performed the serial interception sequence learning (SISL) task with covertly embedded repeating sequences that were much longer than most previous studies: ranging from 30 to 60 (Experiment 1) and 60 to 90 (Experiment 2) items in length. Robust sequence-specific learning was observed for sequences up to 80 items in length, extending the known capacity of implicit sequence learning. In Experiment 3, 12-item repeating sequences were embedded among increasing amounts of irrelevant nonrepeating sequences (from 20 to 80% of training trials). Despite high levels of irrelevant trials, learning occurred across conditions. A comparison of learning rates across all three experiments found a surprising degree of constancy in the rate of learning regardless of sequence length or embedded noise. Sequence learning appears to be constant with the logarithm of the number of sequence repetitions practiced during training. The consistency in learning rate across experiments and conditions implies that the mechanisms supporting implicit sequence learning are not capacity-constrained by very long sequences nor adversely affected by high rates of irrelevant sequences during training.     

Reducing Proactive Interference in Motor Tasks

Abstract

Changing automatized movement patterns often leads to initial performance decrements caused by proactive interference. In this study, we scrutinized whether proactive interference could be reduced by inhibiting the to-be-changed movement pattern by means of a physical movement constraint and verbal inhibition instructions, and whether any of the two interventions may be superior. Skilled typists typed short texts as fast and accurately as possible on a regular QWERTZ keyboard. After baseline measures, a new rule prohibiting the use of the left index finger was introduced. Subsequently, participants took part in either a verbal instruction or an additional motor restriction intervention phase. Results revealed that the original rule change was successful in inducing proactive interference in skilled typists. Most importantly, the two interventions similarly reduced proactive interference both immediately following the rule change and after ten practice sessions. We conclude that reducing proactive interference by means of physical motor restrictions and verbal instructions may be equally effective.     

Reduced asymmetry in motor skill learning in left-handed compared to right-handed individuals

Hemispheric specialization for motor control influences how individuals perform and adapt to goal-directed movements. In contrast to adaptation, motor skill learning involves a process wherein one learns to synthesize novel movement capabilities in absence of perturbation such that they are performed with greater accuracy, consistency and efficiency. Here, we investigated manual asymmetry in acquisition and retention of a complex motor skill that requires speed and accuracy for optimal performance in right-handed and left-handed individuals. We further determined if degree of handedness influences motor skill learning. Ten right-handed (RH) and 10 left-handed (LH) adults practiced two distinct motor skills with their dominant or nondominant arms during separate sessions two–four weeks apart. Learning was quantified by changes in the speed–accuracy tradeoff function measured at baseline and one-day retention. Manual asymmetry was evident in the RH group but not the LH group. RH group demonstrated significantly greater skill improvement for their dominant-right hand than their nondominant-left hand. In contrast, for the LH group, both dominant and nondominant hands demonstrated comparable learning. Less strongly-LH individuals (lower EHI scores) exhibited more learning of their dominant hand. These results suggest that while hemispheric specialization influences motor skill learning, these effects may be influenced by handedness.     

Proactive and retroactive effects of negative suggestion

The negative effects of false information presented either prior to (proactive interference; PI) or following (retroactive interference; RI) true information was examined with word definitions (Experiment 1) and trivia facts (Experiment 2). Participants were explicitly aware of which information was true and false when shown, and true-false discrimination was evaluated via multiple-choice tests. Negative suggestion, defined as poorer performance on interference items than noninterference (control) items, consistently occurred when the wrong information followed the correct information (RI) but not when it preceded the correct information (PI). These effects did not change as a function of retention interval (immediate, 1 week, or 3 weeks) or number of incorrect alternatives (1 or 3). Implications of this outcome for experiencing incorrect information in both academic and nonacademic situations are considered.     

Acquisition of Effector-Specific and Effector-Independent Components of Sequencing Skill

In a serial reaction time task, participants practiced a repeating sequence with 1 hand. In interleaved blocks, they responded to random sequences with the other hand. Experiment 1 was composed of 5 sessions, each consisting of 30 blocks. Intermanual transfer, reflecting a hand-independent component of sequence knowledge, increased across session. A smaller but significant, nontransferable, and hand-specific component was evident in each session and did not increase with practice. Experiment 2 comprised only 1 session. Uninterrupted practice (no interleaved random blocks) improved hand-independent sequence learning in comparison with interrupted practice (as implemented in Experiment 1), whereas hand-specific sequence learning was unaffected by this between-subjects manipulation. These findings suggest separate mechanisms for effector-independent sequence learning and effector-specific acquisition of optimized response coarticulation.     

Are precues effective in proactively controlling taboo interference during speech production?

ABSTRACT

This research investigated whether precues engage proactive control to reduce emotional interference during speech production. A picture-word interference task required participants to name target pictures accompanied by taboo, negative, or neutral distractors. Proactive control was manipulated by presenting precues that signalled the type of distractor that would appear on the next trial. Experiment 1 included one block of trials with precues and one without, whereas Experiment 2 mixed precued and uncued trials. Consistent with previous research, picture naming was slowed in both experiments when distractors were taboo or negative compared to neutral, with the greatest slowing effect when distractors were taboo. Evidence that precues engaged proactive control to reduce interference from taboo (but not negative) distractors was found in Experiment 1. In contrast, mixing precued trials in Experiment 2 resulted in no taboo cueing benefit. These results suggest that item-level proactive control can be engaged under certain conditions to reduce taboo interference during speech production, findings that help to refine a role for cognitive control of distraction during speech production.