Attentional requirements for location and distance of movement: encoding and recognition

The purpose of this experiment was to study the early processing stages of encoding and recognition of slow movement in a short-term motor-memory paradigm. These stages were examined by determining whether Laabs' (1973) differential decay rates for location of movement and distance of movement could be replicated when the interfering activity was performed during the criterion and replication movements. 20 subjects performed a linear-positioning task in a 2 X 2 X 2 (count X movement type X retention interval) experimental design. 10 subjects in one condition counted backwards by 3s during the criterion and replication movements. There were no detrimental effects for location and distance-cue reproduction when attention was shared with counting backwards. Like Laabs' results, location of movement was maintained over the 15-sec. interval while distance of movement spontaneously changed. These results supported the notion that the early stages of encoding and recognition of cues for movement can occur unaffected by a secondary task.     

Preselection and response biasing in short-term motor memory

Two experiments were performed comparing preselected (subject defined) and constrained (experimenter defined) movements. In the first experiment, subjects made reproduction responses immediately or under unfilled and filled 15-sec retention intervals. Results indicated that recall of preselected movements was clearly superior until the interpolation of information processing activity. In addition, preselected movements demonstrated no forgetting over a 15-sec retention interval while constrained movements evidenced spontaneous memory lass, suggesting that preselected movements possess a stronger representation in memory. The second experiment examined this interpretation in a response biasing paradigm. Subjects made criterion responses under preselected or constrained conditions, while the interpolated movement was always in the constrained mode and ± 40 deg from the criterion. The subjects' task was to attend to both movements and recall each when instructed. While preselected recall was clearly superior' to constrained recall, response biasing was clearly evident in both. The failure to find differential biasing effects was discussed in terms of the relative trace strength hypothesis (Stelmach & Welsh, 1972).     

The relationship between the number of presented stimuli and prospective duration estimates: The effect of concurrent task activity

The attention/distraction models of prospective time estimation predict either a negative relationship or an independence between duration estimates and the number of stimulus events presented during the time period, but not a positive relationship. Two experiments examined this relationship under prospective conditions. Lists of words were presented during a 60-sec time period at either a fast or a slow rate. Subjects either passively viewed the words or actively responded by performing either a graphemic or a semantic classification task on each word. To measure subjective duration, the method of magnitude estimation was used in Experiment 1 and the method of reproduction was used in Experiment 2. Time estimates were independent of the number of presented words in the passive viewing condition, and negatively related in the classification task conditions. Furthermore, the two classification tasks had similar effects on time estimates. These findings are consistent with the attentional models of prospective timing, and they question the robustness of earlier findings of a positive relationship between time estimates of moderately long intervals and the number of presented stimuli under conditions of minimal processing of the interval events.     

Memory Characteristics of Kinesthetic Information

Several kinesthetic cues may underlie the retention of movements: joint position receptors, muscle stretch receptors, tendon stretch receptors, cutaneous senses, duration of movements, and motor outflow all provide cues. An attempt was made to separate subsets of cues used for movement reproduction by varying the characteristics of the movements. Ss reproduced either the end Location of a movement or the Distance plus Location. The original and reproduction movements involved either the same or different muscle tensions. These manipulations failed to result in different retention characteristics. In all cases there was little loss of accuracy over a 7-sec. retention interval unless the retention interval was filled with a distracting task. These results are quite different from those of a number of other studies of movement retention, suggesting that different cues do have different retention characteristics.     

Interference with spatial working memory: An eye movement is more than a shift of attention

In the present experiments, we examined whether shifts of attention selectively interfere with the maintenance of both verbal and spatial information in working memory and whether the interference produced by eye movements is due to the attention shifts that accompany them. In Experiment 1, subjects performed either a spatial or a verbal working memory task, along with a secondary task requiring fixation or a secondary task requiring shifts of attention. The results indicated that attention shifts interfered with spatial, butnot with verbal, working memory, suggesting that the interference is specific to processes within the visuospatial sketchpad. In Experiment 2, subjects performed a primary spatial working memory task, along with a secondary task requiring fixation, an eye movement, or an attention shift executed in the absence of an eye movement. The results indicated that both eye movements and attention shifts interfered with spatial working memory. Eye movements interfered to a much greater extent than shifts of attention, however, suggesting that eye movements may contribute a unique source of interference, over and above the interference produced by the attention shifts that accompany them.     

Coding processes in preselected and constrained movements: effect of vision

Three experiments were conducted in which visual information was manipulated either at the endpoint or during preselected, subject defined and constrained, experimenter-defined movements. In Experiments 1 and 2 the subject's task was to reproduce the movement in the absence of vision. Augmenting the terminal location of the criterion movement with vision had no differential effect on reproduction in Experiment 1, although preselected movement accuracy was significantly superior to constrained. Providing vision throughout the criterion movement in Experiment 2 not only failed to improve the accuracy of constrained movements but decreased reproduction performance in preselected movements. In Experiment 3 procedures were adopted to control the allocation of the subjects' attention during the criterion movement. The subjects reproduced by vision alone, movement alone, or with both visual and movement information available. When subjects were informed of the modality of reproduction prior to criterion presentation, they were able to ignore concurrent input from vision and attend to movement information. In the absence of precues visual information was spontaneously attended. The data were interpreted as contrary to closed-loop assumptions that additional information necessarily enhances the strength of a motor memory representation. Rather, they can be accommodated in terms of Posner, Nissen and Klein's (1976) theoretical account of visual dominance and serve to illustrate the importance of selective attention effects in movement coding.     

Adaptation to prisms: Do proprioceptive changes mediate adapted behaviour with ballistic arm movements?

In Experiment I subjects pointed repeatedly at a target viewed through laterally displacing prisms and received terminal visual feedback. In one task the pointing movements were slow (proprioceptively controlled), and in the other they were fast (pre-programmed). In both tasks adaptation proceeded at the same rate and to the same level of performance. Following fast pointing with prisms a large amount of arm-body adaptation was found with slow and fast test movements, while following slow pointing with prisms a large amount of arm-body adaptation was found with slow test movements, but only a small amount with fast test movements. The result suggests that adapted behaviour with preprogrammed movements is not mediated by a proprioceptive change. In Experiment II pointing movements were passive. No arm-body adaptation was found with fast test movements, and, contrary to expectation, only a small amount with slow test movements.     

Memory for Constrained and Preselected Movement Location and Distance

These experiments assessed the interrelationship between location and distance cues in the coding of movements. In separate experiments subjects recalled either the terminal location or the distance of constrained (Experiment 1) or preselected (Experiment 2) movements following a 15-sec retention interval. Changes in direction amd amplitude of starting position were used to ascertain whether recall errors were related to these changes. The findings of both experiments indicated that location and distance were recalled with similar accuracy when the starting position was identical for the criterion and recall movement. However, analysis of constant errors when the recall starting position was varied in either direction clearly indicated neither terminal location nor distance are coded independently, and memory for movement is based on an interaction between these cues.     

Age Differences on a Coincident Anticipation Task

Two experiments were performed as an initial attempt to explain age related limitations in response accuracy on a coincident anticipation task. Five- to 9-year-old boys and adult males participated in each experiment. They made horizontal arm movements in response to stimuli from a Bassin Anticipation Timer. The results of Experiment I confirmed the findings of previous studies, which showed that young children respond early to slow moving stimuli. They were most accurate at intermediate speeds; their responses deteriorated as speed was increased. Older children and adults were more accurate at slow to intermediate speeds; their performances also declined at fast stimulus velocities. Experiment II examined use of a stereotypic or default movement speed as an explanation for these results, particularly for young children. A most comfortable movement pace was determined for each subject and was used as a baseline speed for a subsequent timing task. Four other stimuli were selected in 0.8 mph increments from the baseline speed (two faster, two slower). In addition, selected trials for 6 subjects at each age were filmed at 32 fps. X-coordinates for these trials were obtained and smoothed at 5 Hz. Movement time data suggested that 5-year-olds used a preferred or stereotypic speed, since they were accurate only when responding to their baseline speed. Older subjects matched stimuli up to and including their baselines. Kinematic characteristics confirmed the general notion of preferred speed for 5-year-olds. These same measures demonstrated that older subjects were increasingly adaptable in their responses, despite a failure to respond more accurately. Consequently, the term “preferred speed” lacks generality as an explanatory concept. Age-related shifts in the ability to modify components of a response, like average movement velocity and number of corrections, were used to explain accuracy differences.     

Age difference on a coincident anticipation task: influence of stereotypic or "preferred" movement speed

Two experiments were performed as an initial attempt to explain age related limitations in response accuracy on a coincident anticipation task. Five- to 9-year-old boys and adult males participated in each experiment. They made horizontal arm movements in response to stimuli from a Bassin Anticipation Timer. The results of Experiment l confirmed the findings of previous studies, which showed that young children respond early to slow moving stimuli. They were most accurate at intermediate speeds; their responses deteriorated as speed was increased. older children and adults were more accurate at slow to intermediate speeds; their performances also declined at fast stimulus velocities. Experiment ll examined use of a stereotypic or default movement speed as an explanation for these results, particularly for young children. A most comfortable movement pace was determined for each subject and was used as a baseline speed for a subsequent timing task. Four other stimuli were selected in 0.8 mph increments from the baseline speed (two faster, two slower). In addition, selected trials for 6 subjects at each age were filmed at 32 fps. X-coordinates for these trials were obtained and smoothed at 5 Hz. Movement time data suggested that 5-year-olds used a preferred or stereotypic speed, since they were accurate only when responding to their baseline speed. older subjects matched stimuli up to and including their baselines. Kinematic characteristics confirmed the general notion of preferred speed for 5-year-olds. These same measures demonstrated that older subjects were increasingly adaptable in their responses, despite a failure to respond more accurately. Consequently, the term "preferred speed" lacks generality as an explanatory concept. Age-related shifts in the ability to modify components of a response, like average movement velocity and number of corrections, were used to explain accuracy differences.     

Effect of imagined movement speed on subsequent motor performance

Researchers realize that motor imagery (MI) duration is closely linked to actual motor action duration. In 2 experiments, the authors investigated the effect of changing MI speed on actual movement duration over a 3-week training period. Experiment 1 involved 2 series of body movements that 24 participants mentally performed faster or slower than their actual execution speeds. The fast MI group's actual times decreased on subsequent performance. Participants in Experiment 2 were 21 skilled athletes who increased (decreased) their well-rehearsed actual movement times after MI training at a slow (fast) speed. The effect was task-related, however: MI affected only self-initiated movement. The effect of MI on actual speed execution supports the ideomotor theory because anticipation of sensory consequences of actions is mentally represented.     

Retention Characteristics of Motor Short-Term Memory Cues

The retention characteristics of several cues thought to underlie movement reproduction ability were examined and the results were discussed in terms of two models of motor short-term memory (Laabs, 1973; Pepper & Herman, 1970). Trace decay was indexed by constant error and not variable error. It appeared that the movement cues studied all had access to the central processing capacity in that forgetting did not occur until rehearsal was blocked by the introduction of a secondary task. However, there was some evidence to indicate that different cues are centrally represented in varying degrees of exactness. In this respect reliance on active movement cues and location cues produced better reproduction than passive movement and distance cues, respectively. The existence of an adaptation level established from the range of movement utilized was supported, and short movements were more dependent on central processing capacity than were long movements.     

Attention demands of movements as a function of their duration and velocity

The attention demands of initiating and controlling discrete movements were examined as a function of their movement time (MT) and average movement velocity. Experiment 1 showed that the attention required to execute a movement decreased as MT decreased, although Experiment 2 through independently manipulating MT and movement velocity, revealed that movement velocity is the key determiner of attention demands rather than MT. The attention demands of preparing a high velocity movement are greater than during its execution with the reverse being the case for relatively slow velocity movements. The results are compatible with the view that it is the initiation of error corrections that are attention demanding (Keele 1973).     

Encoding specificity principle in motor short-term memory for movement extent

The hypothesis was tested that, when the mode of presentation matches the mode of reproduction in memory for movement extent, there is less error in reproduction than when the modes are not matched. Female undergraduates (n = 24) were tested under active and passive criterion movements presented either under preselected or constrained conditions. All subjects underwent 36 trials involving the combination of three retention conditions (immediate, 20-sec unfilled, and 20-sec filled) and two reproduction conditions (active and passive). Results for absolute error showed that for constrained presentations, when the mode of presentation and the mode of reproduction were the same, accuracy was greater than when the modes of presentation and reproduction were different.     

Reproducing the end location of a positioning movement: the long and short of it

Two experiments were conducted in an attempt to determine the conditions under which shifts in the starting position of a linear positioning response influenced the reproduction of the end location of movements of various lengths. In Experiment 1, response bias (i.e., shift in constant error) was affected by the direction of the shift in starting position between presentation and recall. For short (20 cm) and medium (50 cm) length movements, this relationship was evident regardless of hand used (left or right), direction of the movement (left to right or right to left), and length of the retention interval (5 or 45 s). However, no relation between response bias and the direction of the starting position shifts was apparent for long (80 cm) movements. The results of Experiment 2 in which more movement lengths were used revealed a response bias that corresponded to shifts in starting position primarily during the first few reproductions of the two shortest movements (20 and 30 cm). However, no systematic bias was evident for any length movement after three reproduction attempts. Possible strategies used by subjects to reproduce the end location of movements of various lengths were discussed.     

Cognitive Strategies and Short-term Memory for Movement Distance and Location

A number of researchers (e.g. Kerr, 1978; Walsh, Russell, Imanaka, & James, 1979) have previously demonstrated interference between location and distance information in motor short-term memory. This interference manifests itself in a characteristic pattern of undershooting and overshooting, with reproduction movement location being drawn in the direction of criterion movement distance and, conversely, the distance of reproduction movements being influenced by the terminal location of the criterion movement. We investigated the effects of different cognitive strategies upon the appearance of this location-distance interference during the reproduction of movement location (Experiment 1) and distance (Experiments 2 and 3) in a linear arm positioning task. Experiment 1 compared performance in location reproduction between two strategy groups differing in the availability of explicit information about the change in starting position. The characteristic undershooting-overshooting interference pattern was observed for the group without the explicit information about the change in starting position but disappeared for the group in which explicit information about the change in starting position was provided. Experiment 2 examined the systematic undershooting-overshooting pattern in distance reproduction for a location strategy (involving some extrapolation of the start and end locations), a counting strategy, and a distance sense strategy (involving the use of visual imagery). The systematic response bias pattern disappeared when the subjects used a location strategy but was clearly observed for the subjects using the other two strategies. This finding was generally confirmed by Experiment 3, which showed a typical undershooting-overshooting pattern in distance reproduction for a counting/distance sense strategy but not for two location strategies (a general location and an explicit location strategy). The location strategies differed in the availability of explicit information about starting and end locations for both the criterion and reproduction movements. The results from these three experiments indicate that explicit information about the start andlor end locations prevents the usual interference between location and distance information from arising in movement reproduction. The notions of automatic and controlled processing and cerebral hemispheric specialization are discussed as potential explanations of these results and of the interference typically observed in motor short-term memory between distance and location information.     

Imagery ability in recall of distance and location information

The role of visual imagery in short-term retention of movement end locations and distances was examined by comparing performances of subjects with extreme scores on the space relations section of the Differential Aptitude Test. Twelve HIGHS and twelve LOWS were tested on reproduction accuracy of six distances and six end locations immediately following presentation a 30-sec rest, a 30 sec imaginal rehearsal condition, and a 30-sec imaginal distraction condition. Initial analysis of the data provided little support for the hypothesis that HIGHS would reproduce criterion locations with more accuracy than LOWS. However, when scores of HIGHS reporting use of an imaginal coding strategy (HIGHS) were compared with LOWS who did not (LOWS), several expected findings were disclosed. HIGHS reproduced end locations with significantly less error in the immediate and imaginal rehearsal conditions, and as expected, accuracy scores for HIGHS and LOWS did not differ for the distance task. The findings suggest that when subjects employ an imaginal coding strategy, visual imagery ability may be an important factor in the retention of location information, but of little functional significance in the recall of distance.     

Waking ultradian rhythms of performance and motility in hyperkinetic and normal children

Waking ultradian rhythms in a visual performance task (detections and false positives) and in motility (global body movements and segmental limb movements during the task, and segmental limb movements during off-task periods) were examined in groups of nonmedicated hyperkinetic (HK) children (N = 11) and matched normal controls (N = 11). Testing was conducted for 5 minutes every 15 minutes (with 10-minute "rest periods") over a 6-hour period on 2 consecutive days. Increased limb movement (p less than .01) during off-task periods on both days. Increased limb movement in HK subjects during the task was marginally significant (p less than .06) on one day. False positives and global body movements failed to differentiate the groups. With regard to ultradian rhythmicity, some subjects in both groups showed evident ultradian peaks, which were present across a wide range of frequencies in one or more variables. There were no significant differences in the incidence of the period of evident ultradian peaks between the two groups.     

Reproducing the End Location of a Positioning Movement

Two experiments were conducted in an attempt to determine the conditions under which shifts in the starting position of a linear positioning response influenced the reproduction of the end location of movements of various lengths. In Experiment 1, response bias (i.e., shift in constant error) was affected by the direction of the shift in starting position between presentation and recall. For short (20 cm) and medium (50 cm) length movements, this relationship was evident regardless of hand used (left or right), direction of the movement (left to right or right to left), and length of the retention interval (5 or 45 s). However, no relation between response bias and the direction of starting position shifts was apparent for long (80 cm) movements. The results of Experiment 2 in which more movement lengths were used revealed a response bias that corresponded to shifts in starting position primarily during the first few reproductions of the two shortest movements (20 and 30 cm). However, no systematic bias was evident for any length movement after three reproduction attempts. Possible strategies used by subjects to reproduce the end location of movements of various lengths were discussed.     

The coding of constrained and preselected movement distance: Same-limb versus switched-limb reproduction

Three experiments were conducted to investigate the codes subserving the retention of movement extent information. Each experiment compared preselected and constrained movements in two independent movement tasks: same-limb reproduction and switched-limb reproduction. When movement direction was the same for both criterion and reproduction movements (experiment 1), same-limb reproduction was more accurate than switched-limb performance. With movement direction altered, however, switched-limb reproduction was equal to same-limb reproduction (experiment 2). These results were confirmed in experiment 3 which manipulated both movement direction and reproduction limb in a within-subject design. Furthermore, while preselected reproduction was superior to constrained reproduction in all three experiments, the two groups were not differentially affected by either the movement task or direction variables. The overall findings were interpreted as providing support for a multiple-cue memorial representation of movement extent and the notion of coding flexibility.