M. T. Turvey

Phase transitions and critical fluctuations in the visual coordination of rhythmic movements between people

By watching each others lower oscillating leg, 2 seated Ss kept a common tempo and a particular phase relation of either 0 degrees (symmetric mode) or 180 degrees (alternate mode). This study investigated the differential stability of the 2 phase modes. In Experiment 1, in which Ss were instructed to remain in the initial phase mode, the alternate phase mode was found to be less stable as the frequency of oscillation increased. In addition, analysis of the nonsteady state cycles revealed evidence of a switching to the symmetric phase mode for the initial alternate phase mode trials. In Experiments 2 and 3, Ss were instructed to remain at a noninitial phase angle if it was found to be more comfortable. The transition observed between the 2 phase modes satisfies the criteria of a physical bifurcation--hysteresis, critical fluctuations, and divergence--and is consonant with previous findings on transitions in limb coordination within a person.

1 On the Concept of Coordinative Structures as Dissipative Structures: I. Theoretical Lines of Convergence*

In this paper we pursue the argument that where a group of muscles functions as a single unit the resulting coordinative structure, to a first approximation, exhibits behavior qualitatively like that of a force-driven mass-spring system. Data are presented illustrating the generative and context-independent characteristics of this system in tasks that require animals and humans to produce accurate limb movements in spite of unpredictable changes in initial conditions, perturbations during the movement and functional deafferentation. Analogous findings come from studies of articulatory compensation in speech production. Finally we provide evidence suggesting that one classically-defined source of information for movement, namely proprioception, may not be dimension-specific in its contribution to coordination and control.In this paper we pursue the argument that where a group of muscles functions as a single unit the resulting coordinative structure, to a first approximation, exhibits behavior qualitatively like that of a force-driven mass-spring system. Data are presented illustrating the generative and context-independent characteristics of this system in tasks that require animals and humans to produce accurate limb movements in spite of unpredictable changes in initial conditions, perturbations during the movement and functional deafferentation. Analogous findings come from studies of articulatory compensation in speech production. Finally we provide evidence suggesting that one classically-defined source of information for movement, namely proprioception, may not be dimension-specific in its contribution to coordination and control.

Self-Organization of Cognitive Performance

Background noise is the irregular variation across repeated measurements of human performance. Background noise remains after task and treatment effects are minimized. Background noise refers to intrinsic sources of variability, the intrinsic dynamics of mind and body, and the internal workings of a living being. Two experiments demonstrate 1/f scaling (pink noise) in simple reaction times and speeded word naming times, which round out a catalog of laboratory task demonstrations that background noise is pink noise. Ubiquitous pink noise suggests processes of mind and body that change each others dynamics. Such interaction-dominant dynamics are found in systems that self-organize their behavior. Self-organization provides an unconventional perspective on cognition, but this perspective closely parallels a contemporary interdisciplinary view of living systems.

Ecological laws of perceiving and acting: In reply to Fodor and Pylyshyn (1981 )*

This paper is both a reply to Fodor and Pt_lyshyn (198 1) and a systematic explication of one of Gibson’s (1979) basic claims, namely, that there are ecological laws relating organisms tc the a.ffordances of the environment. Gibson’s theory of affordances holds great promise for psychology for a number of reasons: it provides a framework for the precise formulation and testing of hypotheses about behavior and perception (e.g. E. J. Gibson, in press; Johnston and Turvey, 1980; Lee, 19110; Shaw and Bransford, 1977); it suggests a way to integrate theOphenomenological and mechanistic aspects of psychology without succumbing to either one-sided point of view (Reed, 1980; Runeson, 1977;Shaw et al., in press;Tua-:rey and Shaw, 1979); and it promises to put psychology back on the track of seeking lawful relations-as Gibson (1967, p. 122) once said, in science: “You either find causal relations or you do not’“.

The motor theory of speech perception reviewed.

More than 50 years after the appearance of the motor theory of speech perception, it is timely to evaluate its three main claims that (1) speech processing is special, (2) perceiving speech is perceiving gestures, and (3) the motor system is recruited for perceiving speech. We argue that to the extent that it can be evaluated, the first claim is likely false. As for the second claim, we review findings that support it and argue that although each of these findings may be explained by alternative accounts, the claim provides a single coherent account. As for the third claim, we review findings in the literature that support it at different levels of generality and argue that the claim anticipated a theme that has become widespread in cognitive science.

Variability and Determinism in Motor Behavior

Abstract In investigations into perception-action systems, variability of observable behavior may be considered to (a) interfere with inquiry, (b) be neither detrimental nor particularly useful to inquiry, or (c) play a crucial role in inquiry. The authors underscore recent suggestions that alternative (c) is a preferred strategy for the study of many motor behaviors. In tutorial fashion, the authors review the concepts of variability and determinism with respect to postural and rhythmic movements. Study of the variability of those behaviors has revealed crucial features suggestive of underlying mechanisms and control, such as particular blends of noise and determinism (piecewise determinism). It has also revealed general lessons (for example, more variable does not mean more random and more controllable does not mean more deterministic) that may extend to other classes of perceptual-motor behavior.

Haptically perceiving the distances reachable with hand-held objects.

Nine experiments are reported on the ability of people to perceive the distances reachable with hand-held rods that they could wield by movements about the wrist but not see. An observed linear relation between perceived and actual reaching distances with the rods held at one end was found to be unaffected by the density of the rods, the direction relative to the body in which they were wielded, and the frequency at which they were wielded. Manipulating (a) the position of an attached weight on an otherwise uniformly dense rod and (b) where a rod was grasped revealed that perceived reaching distance was governed by the principal moment(s) of inertia (I) of the hand-rod system about the axis of rotation. This dependency on moment of inertia (I) was found to hold even when the reaching distance was limited to the length of rod extending beyond an intermediate grasp. An account is given of the haptic subsystem (hand-muscles-joints-nerves) as a smart perceptual instrument in the Runeson (1977) sense, characterizable by an operator equation in which one operator functionally diagonalizes the inertia and strain tensors. Attunement to the invariants of the inertia tensor over major physical transformations may be the defining property of the haptic subsystem. This property is discussed from the Gibsonian (ecological) perspectives of information as invariants over transformations and of intentions as extraordinary constraints on natural law.

An auditory analogue of the Sperling partial report procedure: Evidence for brief auditory storage.

Abstract Three experiments are reported on the partial report of material presented auditorily over three spatially different channels. When partial report was required by spatial location, it was superior to whole report if the cue came less than four seconds after the end of the stimuli (Exp. I). When partial report was required by semantic category (letters/digits) the relation between it and whole report depended on whether the S was asked also to attribute each item to its correct spatial location. When location was required partial report was lower than whole report and showed no significant decay with delay of the partial report indicator (Exp. II), but when location was not required, partial report was superior to whole report for indicator delays of less than two seconds (Exp. III). This superiority was, however, much less than that found in Exp. I when partial report was required by spatial location. These results are compatible with a store which has a useful life of around two seconds and from which material may be retrieved more easily by spatial location than by semantic category.

Visual lexical access is initially phonological: I. Evidence from associative priming by words, homophones, and pseudohomophones

In 9 experiments, a target word (e.g., frog) was named following an associate (TOAD), or a word (e.g., TOWED) or nonword (e.g., TODE) homophonic with the associate. At brief (e.g., 50 ms) stimulus onset asynchronies (SOAs), the 3 primes produced equal associative priming. At a long SOA (250 ms), priming by TOAD was matched by TODE but not by TOWED. Equal priming at brief SOAs by the 3 primes and no priming by orthographic controls (TOLD, TORD) suggests that lexical access is initially phonological. TOWED priming less than TODE at SOA = 250 ms suggests that phonologically activated representations whose input orthography does not match the addressed spelling (available only for words) are eventually suppressed. Phonological constraints on lexical access precede and set the stage for orthographic constraints.

Central sources of visual masking: indexing structures supporting seeing at a single, brief glance.

SummaryWhen two briefly exposed, spatially overlapping visual fields are presented dichoptically, the identifiability of the first field is a J-shaped function of the interval separating their onsets. Three distinct sources of central masking are inferred from the selective influence of variables at different onset asynchronies. In integration through common synthesis, two fields presented at or near simultaneous onset yield one iconic representation. The distinctiveness of this source is inferred from the selective influence of eye dominance at and near simultaneous onset. At longer onset asynchronies, the selective influence of variables such as mask contrast and degree of contour overlap imply a second source of masking. This source was identified with the inhibition of sustained channels by transient channels reported elsewhere. Interchannel inhibition is proposed to affect the fidelity of the iconic representation, but here the imprecision is due to loss of form-relevant information on the first field. At yet longer onset asynchronies, where the fields are phenomenally separate, a third set of variables (e.g., words vs. nonwords and left vs. right visual fields) show their influence. These effects are taken as evidence of a replacement principle: the iconic representation of the second field directs attention from that of the first field. Here, first-field identifiability is constrained by time rather than by impoverished data.In a final series of experiments, central three-field interactions are demonstrated. A field, inserted into the temporal gap between two fields, is perceptually impaired even though it is separated from the first and third fields by intervals at which, individually, neither field is an effective mask. This second-field depression is accompanied by a first-field enhancement. The three sources of central masking are hard pressed to account for the three-field effects.