Explaining “What for” in Motion Analysis Research: A Proposal for a Counterfactual Framework That Is Slightly Different From the Theory of Causation

In motion analysis research, the methodology for estimating the physical processes of human movement is highly developed, but the methodology for interpreting such data is relatively undeveloped. One of the aims of this paper is to demonstrate the importance of developing a conceptual basis for interpreting data about the physical processes of body movement. In this conceptual study, one topic was discussed as a central question: what it means to answer the question what a certain movement technique is aimed for. We first introduced the distinction between explanations from the perspective of causes and explanations from the perspective of purposes as a mode of explaining events, and pointed out the importance of explanations from the perspective of purposes. We next argued that by taking the perspective of whether a given movement technique leads to a desired outcome in comparison to other movement techniques, we can expect to interpret what a given movement technique is for based on objectively observable information rather than the subjective intentions of the athlete. In addition, we discussed how the criterion movement patterns should be defined when assessing the fitness for purpose of a given movement technique in terms of its consequences. In this regard, our argument is that it is necessary to take into account that the exact same movement pattern cannot be performed every time, even for the same motor task, and that there are multiple options for how to define the set of possible movement patterns that can be performed. Our discussion reveals the peculiarity of grasping the meaning of movement techniques, and therefore suggests that there is a substantial need for motion analysis researchers to deepen their conceptual analysis to understand the nature of this issue.

Attention and Visual Dominance in Motor Learning

Two experiments examined the role of attention in visual dominance during motor learning. On the movement task 10 acquisition trials were given; each included a movement presentation and a blindfolded reproduction. After completion of acquisition trials and a 5-min. interval, subjects were given 5 retention trials with reproduction attempts only. In Exp. 1, subjects receiving only kinesthetic information during movement presentation reproduced criterion movement length more accurately than subjects receiving visual and kinesthetic information. Other subjects, presented both visual and kinesthetic stimuli for the movement, were given instructions to ignore vision and focus on kinesthesis. These subjects exhibited no effects of visual dominance in reproductions. In Exp. 2, subjects were presented visual and kinesthetic stimuli during half of the movement presentations and only kinesthetic stimuli during the other half. They did not exhibit the effects of visual dominance in reproductions. Such effects in motor learning may be modified by manipulation of attention or an alternating presentation of specific sensory stimuli.

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 and/or 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.

Visual Dominance in a Lateral Plane Motor Learning Task

Visual dominance was investigated in a motor learning task with the criterion movement being in the lateral plane of the body. The criterion movement was a 10-in. abduction of the arm. All subjects received four presentation trials for the criterion movement in each of the following conditions: dominant rotated arm, dominant unrotated arm, nondominant rotated arm, and nondominant unrotated arm. Three independent groups of 10 college-age subjects differed according to sensory stimuli given during presentation trials. The Kinesthetic group was blindfolded for presentation trials. The Visual and Kinesthetic group was unblindfolded for presentation trials. The Alternating group was blindfolded on half of the presentation trials and unblindfolded on the other half. All subjects carried out five blindfolded reproduction trials for each of the four conditions. Absolute error for the length of the reproduced movements was measured and no significant difference between groups was found. This suggests that visual dominance is reduced in movements outside the frontal plane when focal vision is not used. Planned comparison testing indicated the Alternating group was significantly more accurate than the Visual and Kinesthetic group.

Measurement Bias in Representing Accuracy of Movement on Linear-Positioning Tasks

A short-term memory paradigm was employed to contrast differences in accuracy of recall of three groups of children who ranged in age from 7 to 16 yr. The experimental task required reproduction of a preselected criterion movement of the arm/hand on a linear positioning device. However, the relatively sizeable age differences between groups were associated with marked disparity in arm lengths. Such disparity is typically not represented by a linear or scalar measure of movement. Since movement of the limbs of the body takes place in an arc of a circle, an angular representation of movement at the primary joint (shoulder) seemed a plausible alternative. This representation was achieved by transposing the raw linear measures into an angle which fully considers differential arm lengths. The results of the linear analyses of absolute error indicated that the 7- to 9-yr.-old group was significantly inferior in accuracy of recall to both the 10- to 12- and 14- to 16-yr.-old groups. Also, the 7- to 9-yr.-old group did not appear to rehearse spontaneously as did the older children. Data transposed into an angular form yielded quite different results from the linear ones reported. In this instance the 7- to 9-yr.-old group remained significantly inferior in accuracy of recall to the 14- to 16-yr.-old group but not the 10- to 12-yr.-olds. Of most interest is that the linear evidence for spontaneity of rehearsal in the two older groups was not sustained by the angular data.

The Functional Equivalence of Imagery and Movement

A method of investigating mental imagery is presented which shows that movements and imagery of movements are functionally equivalent. Experiment I uses a short-term-motor-memory linear positioning task in which a novel movement interpolated between initial presentation and recall of a criterion movement length can bias recall. It was predicted that if a similar bias occurred when the interpolated novel movement was imagined rather than performed, then imagery of movements had effects on memory which were functionally similar to producing movements. The results showed that imagery for movements did produce a similar bias. In Experiment II a second order interference task was introduced while instructions to imagine movements were carried out. It was predicted that if imagery for movements were based on the visual/perceptual system then a simultaneous visual inspection task should inhibit imagery. If imagery were based on the motor system though, a simultaneous motor task should prohibit imagery. The results showed that a visual task inhibited imagery. The role of visual imagery in movement control is discussed in terms of spatial representations.

Complex Movement Patterns: Learning Retention and Sources of Error in Recall

In this study of kinaesthesis, the learning, retention, and recall of complex patterns was examined. Subjects were blindfolded, held a stylus in the right hand, and moved around stencil patterns, either actively or passively. The patterns were recalled with a free active movement of the right hand, after various amounts of practice, immediately or after a 60–s interval, once or twice in succession, with and without visual guidance. The shape and size of the drawings was compared with the criterion patterns. The effect of practice varied depending on whether the criterion movement was active or passive, and on the measure of recall performance. Even when the criterion patterns were freely practised, the recall traces showed large errors in shape and systematic shrinkage in size, and there were large individual differences. Regardless of these errors, recall performance was reliable. The effect of an unfilled retention interval varied as a function of practice. When the patterns were recalled under visual guidance, there was no shrinkage in the size of the drawings.

Movement Reproduction as a Function of Efferent Cues and cognitive Plans

The reproduction of linear movements was studied as a function of the availability of efferent cues and a cognitive plan during criterion movements and of efferent cues during test movements. Nine females were used as subjects in each cell of a between-subject factorial design. The presence of a cognitive plan during or as a result of the criterion movement lead to more accurate movement reproduction than when a plan was not available. If efferent cues were present during a criterion movement, then the presence of efferent cues during the test movement facilitated accurate movement reproduction. These results have implications both for theories of motor control and for applied motor learning and control situations.

Perceptions of Movement Patterns: Recall of Movement

The present study attempted to characterize the perception, retention, and recall of kinaesthetic information regarding movement sequences (patterns). An attempt was made to draw on and extend conclusions relevant to simple movements (movement amplitude). One group of 10 blindfolded subjects recalled criterion movement patterns that had been actively commanded and 10 subjects recalled passively induced movements. The following conclusions were made. (1) Previous reports of algebraic errors in the recall of simple movement amplitudes are consistent with the finding that criterion perimeter, area, and depth of features were underestimated when recalled. (2) Measures of the accuracy of kinaesthetic perception do not alone account for the generally low level of pattern recall, the large range of individual differences or the underestimation of amplitude. The process of percept formation and of translating a percept into recalled movement are implicated. (3) Conclusions based on the short-term retention and recall of simple movements do not account for the coding, retention, and recall of movement sequences (patterns). (4) Percepts were formed, and patterns were recalled as a sequence of features but not as a sequence of key positions. (5) No direct difference was demonstrated between the recall of actively commanded and passively induced criterion movement patterns. However, the finding of a high gross angle change in the active condition was explained in terms of an unfavourable interaction between corollary discharge and sensory information.

Adaptation Level and Retroactive Interference in Motor Short-Term Memory

5 groups of 10 subjects were required to make and recall a linear self-generated arm-positioning movement. 4 of the groups made and recalled 4 interpolated self-generated positioning movements before the recall of the criterion was attempted. The lengths of the interpolated movements relative to the criterion varied from group to group. For one group all interpolated movements were longer, for another they were all shorter, and two groups produced alternating shorter and longer movements. Results indicated a significant difference in percentage algebraic error at recall of the criterion movement between the groups experiencing longer and experiencing shorter interpolated movements. The evidence is suggestive of two components in retroactive design studies, interference and adaptation level.