Auditory information is beneficial for adults with Down syndrome in a continuous bimanual task

Much recent research using discrete unimanual tasks has indicated that individuals with Down syndrome (DS) have more difficulty performing verbal-motor tasks as compared to visual-motor tasks (see Perceptual-Motor Behavior in Down Syndrome, Human Kinetics, Champaign, IL, 2000, p. 305 for a review). In continuous tasks, however, individuals with DS perform better when movement is guided by auditory information compared to visual information (Downs Syndr.: Res. Prac. 4 (1996) 25; J. Sport Exercise Psy. 22 (2000) S90). The aim of the present study was to investigate if there are any differences for adults with DS between visual, auditory and verbal guidance in a continuous bimanual task. Ten adults with DS, 10 adults without DS and 10 typically developing children drew lines bimanually towards the body (down) and away from the body (up) following three different guidance conditions: visual (flashing line), auditory (high tone, low tone), and verbal (“up”, “down”). All participants produced mostly in-phase movements and were close to the 1000 ms target time for all guidance conditions. The adults with DS, however, displayed greater variability in their movement time, movement amplitude and bimanual coordination than adults without DS. For all groups, the left hand was slower and more variable in producing the lateral movements than the right hand. The results regarding guidance information suggest that auditory information is beneficial for repetitive bimanual tasks for adults with DS. Possible mechanisms that cause these results will be discussed.     

Saccadic eye movements and dual-task interference

Four dual-task experiments required a speeded manual choice response to a tone in a close temporal proximity to a saccadic eye movement task. In Experiment 1, subjects made a saccade towards a single transient; in Experiment 2, a red and a green colour patch were presented to left and right, and the saccade was to which ever patch was the pre-specified target colour. There was some slowing of the eye movement, but neither task combination showed typical dual-task interference (the “psychological refractory effect”). However, more interference was observed when the direction of the saccade depended on whether a central colour patch was red or green, or when the saccade was directed towards the numerically higher of two large digits presented to the left and the right. Experiment 5 examined a vocal second task, for comparison. The findings might reflect the fact that eye movements can be directed by two separate brain systems--the superior colliculus and the frontal eye fields; commands from the latter but not the former may be delayed by simultaneous unrelated sensorimotor tasks.     

Driye-leyel and flexibility in paired-associate nonsense-syllable learning

“High-anxiety” and “low-anxiety” subjects, selected for extreme scores on the Taylor Anxiety Scale, learned a list of paired-associate nonsense syllables in the belief that they were undergoing an intelligence test. Both groups were then given a second list of paired associates to learn, the stimulus-items being the same as those of the first list but the responses being changed. Before the presentation of the second list, half the subjects in each group were given anxiety-increasing instructions and the remaining half were given reassuring instructions.

The results verified two predictions made from Hull's behaviour theory, using the concept of fear or anxiety as a secondary drive:—“high anxiety” subjects took more trials to master the second learning task than “low-anxiety” subjects; and there was a significant interaction between initial anxiety-level and type of instructions, such that “high-anxiety” subjects who received drive-increasing instructions had a worse performance in the second part than all other sub-groups. There was no indication that “low-anxiety” subjects were significantly affected by the type of instructions received. The “high-anxiety” group had greater difficulty than the “low-anxiety” group in learning the first list, but the difference was non-significant.     

Attentional asymmetries during concurrent bimanual performance

An asymmetry of attention was observed when subjects attempted to perform concurrent, relatively independent tasks with the two hands: right-handed subjects performed very much better on a dual task which required them to follow the beat of a metronome with the left while tapping as quickly as they could with the right than with the converse arrangement. It is suggested that attentional strategies which have evolved to allow guidance of interdependent skilled bimanual activities are also used when subjects attempt to perform relatively independent concurrent bimanual movements, which are not observed in the naturally occurring motor repertoire. Thus, interactions between hand, hand preference and nature of task are an important factor in dual task performance.     

After-effects of responding and of withholding responses in C.RT tasks

The effects of response repetition on choice RT were compared in b-reaction and in c-reaction tasks [Experiments I(a) and I(b)]. The difference in RTs for repeated and for non-repeated responses was found to be less for c-reaction than for b-reaction tasks. This seemed to be because in c-reaction tasks subjects can prepare themselves to make the same response on every trial, so that there is little further RT reduction consequent on immediate response repetition. In b-reaction tasks subjects cannot always prepare to make the same response, so that the difference between response repetition RT and responce alteration RT is greater. Experiment II examined transitions between events in a serial, self-paced C.RT task in which subjects made a different response to each of two signals but withheld any response to the onset of a third. In this task responses were faster when they followed other, different responses than when they followed “no go” trials. The results of these experiments allow us to reject, even for very elementary tasks, a simple “S--R connection network” model for the processes involved in the identification of signals and the production of responses to them.     

Study of the energy correlates in the learning of a complex self-paced cyclical skill

This study examines changes in movement parameters and energy expense during the learning of a cyclical task performed on a “ski simulator”. Five subjects performed five training sessions (each of four 4-minute learning periods separated by a 4-minute rest) and then took a post-test one week later. The instructions were to make movements which were “as wide and frequent as possible”. The subjects were filmed on videotape and their oxygen intake was measured. Movement amplitude, movement frequency, oxygen intake, and a “movement cost” index were calculated. The results indicated a significant increase in movement amplitude and oxygen intake and a decrease in movement cost. The movement frequency of all subjects tended towards the same final value. Two simultaneous changes could occur, with large individual differences: an increase in energy expense due to the increase in the amount of work done, a decrease in energy expense due to the increase in movement economy.     

Movement duration does not affect automatic online control

Pisella et al. (2000) have shown that fast aiming movements are automatically modified on-line in response to a change in target position. Specifically, when a movement is less than 300 ms in duration the reach is completed to a target’s new location even when one never intended to respond to the target jump. In contrast, when movements are slower, the reach is completed according to instructions. At present, it is unclear if it is possible for one’s intentions to guide the initial stages of these slow movements. To determine if the intentional control mechanism can guide the initial stages of a slow aiming movement, participants aimed to targets that could jump at movement onset, with a slow and very slow movement time goal. In particular, participants were to point towards (“pro-point”) or away from (“anti-point”) the target jump, with a movement time goal of 500 or 1200 ms. Results showed that in the anti-point condition, movement trajectories first deviated in the same direction as the target jump, followed by a response in the intended (opposite) direction. This suggests that while movement outcome is controlled by the intentional system, even in these slow aiming movements the automatic system is engaged at movement onset.     

Neural correlates of partial transmission of sensorimotor information in the cerebral cortex

Using single neuron recordings in monkey primary motor (MI) cortex, two series of experiments were conducted in order to know whether response preparation can begin before perceptual processing finishes, thus providing evidence for a temporal overlap of perceptual and motor processes.

In Experiment 1, a “left/right, Go/No-Go” reaction time (RT) task was used. One monkey was trained to perform wrist flexion/extension movements to align a pointer with visual targets. The visual display was organized to provide a two-dimensional stimulus: side (an easy discrimination between left and right targets) which determined movement direction, and distance (a difficult discrimination between distal and proximal targets) which determined whether or not the movement was to be made. Changes in neuronal activity, when they were time-locked to the stimulus, were almost similar in the Go and No-Go trials, and when they were time-locked to movement onset, were markedly reduced in No-Go as compared to Go trials.

In Experiment 2, a stimulus-response compatibility (SRC) task was used. Two monkeys were trained to align a pointer with visual targets, on either left or right. In the spatially “compatible” trials, they had to point at the stimulus position, whereas in the “incompatible” trials, they had to point at the target located in the opposite side. For 12.5% of neurons, changes in activity associated with incompatible trials looked like changes in activity associated with movements performed in the opposite direction during compatible trials, thus suggesting the hypothesis of an automatic activation of the congruent, but incorrect response.

Results of both experiments provide evidence for a partial transmission of information from visual to motor cortical areas: that is, in the No-Go trials of the first task, information about movement direction, before the decision to perform or not this movement was made, and, in the incompatible trials of the SRC task, information about the congruent, but incorrect response, before the incongruent, but correct response was programmed.     

“Handedness” and skill

The variability of handedness with different tasks is discussed. Experiments are described which show under what conditions handedness becomes evident. Tasks involving three different levels of complexity were used. The simplest task measured the accuracy with which a particular pressure could be reproduced in isometric contraction of the flexors of the index finger on each side in 21 female subjects. In the second situation, the maximum speed of making an attempted tapping movement under the same conditions, was measured in ten of the same subjects using the same muscle group alternating with its antagonists. The same ten subjects were also tested on an aiming task which provided the third level of complexity. The results suggest that differences in performance between the two sides only occur where “timing” or the serial organization of muscle activity is required and that such differences may be due to training.

Whether handedness is inherited or acquired is briefly discussed, and a second series of experiments using the same tasks as before were carried out on one female and nine male subjects. In this instance, the first two tests were used on the big toe of each side as well as the index finger. The results confirm that differences in performance between the two sides on these tasks can be adequately explained in terms of usage or training.

The hypothesis that “timing” is therefore important in the learning of any movement where serial muscle contractions arc involved was tested and confirmed in a third experimental series. The consistency of timing of the application of force in turning a crank handle at maximum speed was measured in five male subjects before and after training. The implications of the results are discussed in relation to other researches on skills.     

The effect of training and handedness on the performance of two simple motor tasks

In the first experimental series nine right-handed and nine left-handed subjects were tested on each side on two tasks. The first task measured the accuracy of reproduction of pressure in attempted extension of the elbow joint, and the second the speed of oscillation of attempted flexion and extension of the elbow joint. The results showed no significant difference in performance on the two sides in the accuracy task but a significant difference in performance on the speed task.

In the second experimental series the effect of 15-minutes daily training on each of two tasks over a four-week period was investigated on six subjects. The two tasks were the same as those used in the first experimental series, and attempted movement at the metacarpo-phalangeal joint as well as the elbow joint was studied. The mean results of all subjects showed a significant reduction in the mean error of the “accuracy” task over the training period for both the finger and arm. However, further analysis suggests that this may have been due to a clarifying of the subjects' concept of the target value rather than an improvement in his ability to grade the appropriate muscle contractions. A significant increase in the mean speed of oscillation over the training period was also recorded for both finger and arm. This improvement was accompanied in most instances by a corresponding decrease in variation of cycle length of the individual oscillations, which is interpreted as an improvement in the subjects' “timing” of the appropriate muscle contractions.     

Some errors of perceptual analysis in visual search can be detected and corrected

This experiment tried to discover whether people can correct errors which occur because they incorrectly analyse a display to which they have to respond--whether, in fact, they can correct “perceptual” as well as “motor” errors. In a serial, self-paced visual search task, subjects made one response to indicate that a display of five or nine letters contained either of a pair of target letters, and another response when no target was present. Omission errors were much more common than False Identification Errors, but more of them were corrected. Omission errors were detected and corrected faster than False Identification Errors. Typically omission errors were slow responses while False Identification Errors were fast responses. It is possible to deduce that at least some errors resulting from incorrect analysis of a display can be detected and corrected, probably because of an extension of perceptual analysis during, or immediately after, the time when a response to the display is made.     

Experimental finger dyspraxia

Subjects were required to perform discrete finger movements in accordance with a pre-arranged sequence of instructions. In all cases, any movement made by any finger was recorded by means of a constant-speed kymograph equipped with levers designed to record separately the movements of the individual fingers. This experiment was carried out under three conditions: (a) with no vision of the hand; (b) with direct vision of the hand; and (c) with the hand presented in mirror-image. It was found that, whereas deprivation of visual control was without effect on the efficiency of finger movements, presentation of the hand in mirror-image gave rise to significant increases in reaction time of three fingers and to an increase in the percentages of prior and substitute movements of other digits. Phenomena akin to depersonalisation were reported in some cases. It was also found that the rank order of mean reaction times of the five digits was approximately constant under all conditions and that the two fingers with the shortest reaction times were preceded by the fewest movements of other digits. These two digits were also the most frequently moved in advance when movements of other digits were requested and it is suggested that they have a certain “signpost function” in guiding identification of the remaining fingers. Some implications of these results for an understanding of “finger agnosia” are briefly indicated in an Appendix.     

Eye movements and performance during bilateral tracing tasks

To examine the role of current visual monitoring in the between-hand differences in skilled movements, eye movements and errors during bilateral tracing tasks were analyzed in 10 subjects. When subjects traced a horizontal course abductively with both hands, the subject's gaze followed the movement of the right hand, and more errors were observed on the left hand. When subjects traced a vertical course, where fine motor control for alteration of movement direction was necessary, more errors were shown on the left hand despite the alternate visual scan of the two hands. The results were interpreted as showing that the between-hand differences in skilled movements are primarily due to the left hand's poor ability in motor output, and that the differential efficiency in the use of visual monitoring becomes an important factor in the between-hand differences when symmetrical movements of both hands with a low degree of difficulty are required.     

Variations in reflex blink-rate during visual-motor tasks

The influence of the performance of various tasks on the reflex blink rate has been investigated repeatedly, but the results obtained have been somewhat contradictory. More recently, it has been suggested that the reflex blink rate may be a considerable factor in the accuracy with which visual-motor tasks are performed. The aim of the present experiment was to attempt to obtain further evidence on both these questions.

The experiment was carried out in two parts. The main part was done in the laboratory, while a validating experiment was carried out on the road. In the laboratory, subjects were required t o steer a pencil along a moving track which varied in difficulty. The difficulty of the response was varied by using a direct control on some trials and a velocity control on others. Blink rate, errors, and control measurements were recorded throughout. In the road experiment, cine films were taken of the driver's eyes while driving in heavy traffic and in open country.

The results of both experiments show:

(a) That there are marked individual differences in blink rate, the relative order of which is maintained in spite of variations in the actual blink rate.

(b) That there is no relationship between the accuracy with which a particular individual carries out a task of this sort and his blink rate. The rapid “blinker” is no more and no less likely to be accurate than the infrequeiit I “blinker.”

(c) That the actual blink rate for all individuals varies inversely with the difficulty of the task and the amount of control movement necessary. The blink rate decreases as the necessity for detailed visual control of movement increases. Blink rates when driving a car in heavy traffic, or when steering along an oscillating track, are considerably lower than when driving in open country or when following a straight track.

(d) That the adjustment of the blink rate to the difficulty of the task is achieved not only by an alteration in overall blink rate, but also by a change in the distribution of blinking. The blink rate is approximately constant under constant conditions, but when the task is varying in difficulty, blinking occurs just before and just after periods of maximum difficulty, but is completely inhibited during the periods of maximum difficulty itself.     

The influence of previous movement and posture on subsequent posture

An experiment with 21 subjects has confirmed the findings of other investigators that previous posture affects subsequent posture—the phenomenon of postural persistence. There seems also to be a tendency for the arm to be judged horizontal when in fact above the horizon, no matter which posture has been previously adopted—a “constant upwards effect.” It has also been found that the direction of previous movement affects subsequent posture. After movement, an overshooting effect adds to a “constant upwards effect.”

Various explanations of the phenomenon are discussed, and persistence is considered as an anomaly of postural recognition.     

Inducing a Rule in Wason's 2-4-6 Task: A Test of the Information-Quantity and Goal-Complementarity Hypotheses

In the standard 2-4-6 induction task, subjects are instructed to discover the rule generating sequences of three numbers by inventing number triples for which they receive immediate feedback. The rule is “ascending numbers”. Performance is greatly aided with Dual Goal (DG) instructions that ask subjects to discover two rules, one that generates “Dax” triples (equivalent to “yes” instances with Single Goal [SG] instructions) and another that generates “Med” triples (equivalent to “no” instances). The present study eliminates two explanations for this effect suggested by Wharton, Cheng, and Wickens (1993). Experiment 1 tested their Information-Quantity hypothesis that the effect results simply from the DG subjects testing more triples prior to proposing a rule. Our DG subjects were more likely to solve the problem and produced more “negative” triples than SG subjects when both groups generated exactly 15 triples. Two further groups received feedback only after generating all 15 triples, and again DG subjects were more likely to solve the problem and to generate more “negative” triples. Experiment 2 tested Wharton et al.'s Goal-Complementarity hypothesis that success under DG instructions hinges on preserving the complementary representation of the two rules. We compared SG instructions with three types of DG instructions that suggested different types of triples (Dax, Med, both Dax and Med, neither Dax nor Med). DG instructions were more effective in promoting successful rule discovery regardless of differences in rule complementarity. Our analysis of the heterogeneity of the examplars generated with DG instructions in both experiments suggest that success on the 2-4-6 task is as much a consequence of the breadth of hypotheses that subjects entertain as it is a consequence of the testing strategy.     

Short report: Is spatial information encoded automatically in memory?

A dual-task paradigm was used to test Hasher and Zacks' (1979) hypothesis that spatial memory is automatic. Subjects saw two sets of 16 words each, the words being presented singly in random corners of a monitor screen. They were asked to remember the words and the corner in which each word was shown. In addition, subjects were given a concurrent task to perform. This task was either “easy” (counting aloud by ones) or “difficult” (counting aloud by sevens). Attention was focused either on the memory task or on the counting task. Word recognition was better when subjects carried out the easier competing counting task and when subjects concentrated mainly upon remembering the words and their positions. Contingent spatial memory was unaffected by either manipulation, supporting the hypothesis that spatial memory is automatic.     

Response selection errors in spatial choice reaction tasks

In a “Consistent” spatial choice reaction task, the same spatial relationship obtains between each stimulus and its appropriate response. In an “Inconsistent” task this is not so. The present experiment concerns errors in Inconsistent tasks. Duncan (in press) has suggested that, when two spatial S-R relationships are involved in a task, the dominant type of error is a response bearing to the stimulus the wrong one of the two relationships. Duncan's results, however, may be described by a different generalization. Rabbitt and Vyas (1973) have suggested that confusions occur between responses which, when made correctly, bear similar spatial relationships to their stimuli. In the present experiment, a new Inconsistent task is studied. The results support the account of Duncan (in press) but provide no support for that of Rabbitt and Vyas (1973). Partly on the basis of error results, Duncan (in press) proposed a model of response selection in the spatial choice reaction task. Unlike previous accounts, this model is not based on a set of individual “S--R” associations; operations generating sets of S--R pairs are involved.     

An observation on set and visual comparison processes

Tasks involving the comparison of sequentially presented stimulus items to determine identity have generally only required interpretation in terms of simple matching. Some studies have attempted to show effects of selective set in these tasks but with little success except in tasks involving comparison of sentences with pictures. By simplifying the task a reliable set effect is demonstrated, showing that a mismatch of certain stimulus attributes only has an identifiable effect on a subject's reaction-time if he may reasonably be supposed to know that the attribute is critical and is set to examine stimulus items for the attribute. Such conditions result in a relatively fast judgement. The finding suggests that the sequential “same“/“different” judgement is a richer source of data concerning recognition and comparison than has been supposed.     

EEG correlates of cumulative expectancy and subjective estimates of alertness in a vigilance-type task

Occipital EEG was monitored during a slow presentation rate vigilance task. EEG samples were taken for each of 400 task events. The EEG is correlated with increases and decreases in “expectancy” built into the task. Post-trial subjective estimates of alertness parallel the EEG changes. Reaction time to “wanted signals” does not correlate with measures of pre-signal EEG.