Learning as change of coordination dynamics: theory and experiment

Learning of coordination patterns was investigated theoretically from the point of view of a dynamic theory of biological coordination and with reference to recent experiments on the learning of relative timing patterns. The theory is based on theoretical and experimental work showing that coordinated movement is characterized not only by the actually performed pattern of coordination but by an entire dynamics of coordination. Theoretically, such dynamics are captured as equations of motion of relevant collective variables. Experimentally, signatures of these underlying dynamics can be found in the temporal stability of coordination patterns, which can be assessed through various stability measures as well as through processes of pattern change. We argue that not only intrinsic coordination tendencies, but also specific behavioral requirements, be they perceived, memorized, or intended, must be expressed in terms of such dynamics. The concept of behavioral information captures such requirements as part of the coordination dynamics. We expound two hypotheses on the nature of learning in this framework. First, we assume that at each point during the learning process the system is governed by a well-defined coordination dynamics. This equation of motion evolves with learning so as to acquire an attractor solution near the to-be-learned pattern. Second, we hypothesize that this change of the coordination dynamics, captured by the time course of memorized behavioral information, can itself be ascribed to an additional layer of dynamics, the slower learning dynamics. Testable consequences of these views are discussed in the light of recent experimental findings on the learning of a relative phase in rhythmic movement: (a) Learning affects dynamic properties of performed coordination patterns, in particular, their stability; (b) the change of the coordination dynamics due to learning leads to specific changes of behavior also under conditions other than the learned condition, namely, to systematic deviation toward the learned patterns; (c) learning may lead to instabilities in the coordination behavior if initial and learned performance differ sufficiently; and (d) the dynamic properties of the performed coordination patterns are distinct on the two time scales of learning and of performance.     

Converging evidence for the role of relative timing in speech

In an earlier article (Tuller, Kelso, & Harris, 1982a) we suggested that the timing of consonant-related muscle activity was constrained relative to the period between onsets of muscle activity for successive vowels. Here, we reexamine those data based on reservations posed by Barry (1983). Next, we present a kinematic study of articulation that extends and strongly supports our original observations. Finally, we very briefly survey some converging lines of evidence for a functionally significant vowel-to-vowel period in speech and how this may relate to the role of temporal invariance in motor skills in general.     

Categorization of Ambiguous Sentences as a Function of a Changing Prosodic Parameter: A Dynamical Approach

The present study investigates the dynamics of changes in interpretation of ambiguous sentences. The sentences used had alternative interpretations with different surface structures (bracketing). Continua were created by systematic manipulation of prosodic cues (relative foot duration), resulting in stimulus sentences that spanned the range between the two interpretations. Continua were presented to subjects who were requested to indicate as quickly as possible which meaning they perceived. The pattern of responses and response times revealed the presence of hysteresis. That is, when the values of prosodic parameters are congruent with both interpretations, the individual's recent history decides which meaning will be perceived. Thus, we can treat this categorization process as a transition from an initially stable meaning that loses stability with variations in prosody (our control parameter). The same underlying dynamics have been observed in studies of perception of syllables and aspects of visual perception. Apart from demonstrating the same characteristics of pattern formation at various levels of cognition, the study points to the usefulness of the dynamical approach in the investigation of language understanding.     

The influences of stage of leaving school on vocational maturity and realism of vocational choice

Cross-sectional data were provided by 1484 male high school pupils drawn from grades seven to twelve. All subjects completed either the Otis Intermediate Test or the Otis Higher Test, Crites' Vocational Development Inventory (VDI), and the author's Student Survey. Major findings were that: (1) subjects' anticipated stage of leaving school was significantly related to realism of vocational choice-those boys who expected to leave school prior to grade twelve showed higher levels of realism than those going on, in spite of the fact that they tended to be lower in both maturity of vocational choice attitudes (VCA) and intelligence; (2) IQ exercised a complicated mediatory effect on both VCA and realism; and (3) in general, both VCA and realism were linearly related to grade. Taken together, these findings indicated the need to distinguish carefully between VCA and realism as aspects of vocational development. Implications for further research in vocational development are discussed.     

Preselection in short-term motor memory.

Recent studies by Jones (1974) have posited that accurate movements in short-term motor memory (STMM) are mediated by the subject's ability to preset effector mechanisms and monitor their efferent output. Three experiments were conducted to examine this hypothesis. Experiment 1 involved comparisons between the reproduction of the end-location and the reproduction of the distance of a preselected movement. The results revealed that preselected location was superior to preselected distance, indicating that the efference attached to movement extent was not primary. Experiment 2 examined whether location cues were primarily encoded independent of the movement presentation mode. The subjects recalled target locations under preselected, constrained, and passive movement conditions. Recall in the preselected condition was superior to that in the constrained and passive conditions, which showed no difference, suggesting that afferent location information per se was not totally responsible for recall accuracy. Experiment 3 examined the processing requirements of preselected, constrained, and passive location information by filling the retention interval with interpolated processing activity. While preselected location was clearly superior, the three conditions were not differentially affected by processing activity. These overall findings were interpreted as contrary to Jones (1974) and pointed to the importance of preselection in short-term motor memory.     

Memory trace strength and response biasing in short-term motor memory

Two experiments, which attempted to create differential memory trace strengths in a response biasing paradigm, were performed. After the presentation of the criterion location, an interpolated target was presented which was either ±40 deg from the criterion. The S’s task was to attend to both targets and recall each when instructed. The first experiment involved strengthening the criterion trace via repetition (0, 5, or 14 rep.) while the second involved providing additional feedback via visual, auditory, and heightened kinesthetic cues. In the initial experiment, a Repetition by Response Biasing interaction revealed that repetition systematically reduced error shifts at recall. The second experiment found that, in the combined feedback and visual conditions, response biasing was reduced. It seems feasible to suggest that both studies successfully manipulated memory trace strength which appears to be one determiner of error shifts at recall.     

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).     

Are movements prepared in parts? Not under compatible (naturalized) conditions

This set of experiments is concerned with the specification of movement parameters hypothesized to be involved in the initiation of movement. Experiment 1 incorporated the precuing method developed by Rosenbaum in which a precue provided partial information of the upcoming movement before the stimulus to move. Under conditions in which precues were provided by letter symbols and stimuli were color-coded dots mapped to response keys. Rosenbaum found reaction times to be slower for the specification of arm than for direction, and both to be slower than the specification of extent. In Experiment 1, using precue and stimulus conditions that paralleled those employed by Rosenbaum, we obtained very similar findings. The three follow-up experiments extended these findings to more naturalized stimulus-response compatible conditions. We used a method in which precues and stimuli were directly specified through vision and mapped in a one-to-one manner with responses. In Experiment 2, although reacion times decreased as a function of the number of parameters precued, there were no systematic effects of precuing particular parameters. In Experiments 3 and 4, we incorported an ambiguous precue that, while serving to reduce task uncertainty, failed to provide any specific information as to the arm, direction, or extent of the upcoming movement. Initiation times did not systematically vary as a function of the type of parameter precued nor were there significant differences between specific and ambiguous precue conditions. In sum, only in Experiment 1 in which precues and stimuli involved complex cognitive transformations was there support for Rosenbaum's parameter specification model. When we employed highly compatible conditions, designed to reflect a real-world environment, we failed to obtain any tendency for movement parameters to be serially specified. We discuss grounds for suspecting the generality of parameter specification models and propose an alternative approach that is consonant with the dynamic characteristics of the motor control system.     

Coordination dynamics of the horse-rider system

The authors studied the interaction between rider and horse by measuring their ensemble motions in a trot sequence, comparing 1 expert and 1 novice rider. Whereas the novice's movements displayed transient departures from phase synchrony, the expert's motions were continuously phase-matched with those of the horse. The tight ensemble synchrony between the expert and the horse was accompanied by an increase in the temporal regularity of the oscillations of the trunk of the horse. Observed differences between expert and novice riders indicated that phase synchronization is by no means perfect but requires extended practice. Points of contact between horse and rider may haptically convey effective communication between them.