Dynamics of human postural transitions

In the present study, the authors examined transitions between postural coordination modes involved in human stance. The analysis was motivated by dynamical theories of pattern formation, in which coordination modes and transitions between modes are emergent, self-organized properties of the dynamics of animal-environment systems. In 2 experiments, standing participants tracked a moving target with the head. Results are consistent with the hypothesis that changes in body coordination follow typical nonequilibrium phase transitions, exhibiting multistability, bifurcation, critical fluctuations, hysteresis, and critical slowing down. The findings suggest that posture may be organized in terms of dynamical principles and favor the existence of general and common principles governing pattern formation and flexibility in complex systems.     

Organization of compensatory postural coordination patterns

The authors investigated whether compensatory postural coordination patterns are organized according to the same dynamical principles as are nonequilibrium phase transitions. Eight participants were asked to maintain upright balance on a moving platform that was sinusoidally translated in the anterior-posterior direction and was systematically increased and decreased 0.19 Hz as a step function every 10 platform cycles through the frequency range 0.19-1.46 Hz. At low platform frequencies, all participants exhibited small joint angular motions with high variability, and the relative phase between the joint motions exhibited drifting patterns and large fluctuations. As platform frequency increased, the amplitude of joint motion increased systematically and joint-specific oscillatory patterns emerged. The findings provided no evidence for a Hopf bifurcation or hysteresis in the transitions of postural coordination modes, however, or, more generally, a basis for distinguishing the relevance of linear versus nonlinear models of postural control.     

The influence of lying positions and postural control on hand-mouth and hand-hand behaviors in 0-4-month-old infants

The purpose of this study was to verify how and when body position and postural control affect hand-mouth and hand-hand behaviors in infants during their first 4 months of life. Forty healthy infants were positioned in supine, prone and side-lying positions so that frequency and duration of the behaviors were quantified. Postural control when in supine and prone was also analyzed. The prone position elicited hand-mouth behavior in 0-2-month-old infants. The side-lying position elicited hand-mouth behavior in 3-4-month-old infants and hand-hand behavior in 2-4-month-olds. The increased postural control promoted the emergence of hand-hand behavior when in supine, and decreased hand-mouth behavior when in prone. The results show that self-exploratory behaviors may be affected not only by extrinsic constraints, represented by different body positions, but also by intrinsic constraints, represented by characteristic action possibilities and postural control of each age group.     

The influence of postural emotion cues on implicit trait judgements

Perceptions of others’ traits (e.g., trustworthiness or dominance) are influenced by the emotion displayed on their face. For instance, the same individual appears more trustworthy when they express happiness than when they express anger. This overextension of emotional expressions has been shown with facial expression but whether this phenomenon also occurs when viewing postural expressions was unknown. We sought to examine how expressive behaviour of the body would influence judgements of traits and how sensitivity to this cue develops. In the context of a storybook, adults (N?=?35) and children (5 to 8 years old; N?=?60) selected one of two partners to help face a challenge. The challenges required either a trustworthy or dominant partner. Participants chose between a partner with an emotional (happy/angry) face and neutral body or one with a neutral face and emotional body. As predicted, happy facial expressions were preferred over neutral ones when selecting a trustworthy partner and angry postural expressions were preferred over neutral ones when selecting a dominant partner. Children’s performance was not adult-like on most tasks. The results demonstrate that emotional postural expressions can also influence judgments of others’ traits, but that postural influence on trait judgments develops throughout childhood.

     

The influence of complexes on implicit learning

A century ago, Jung looked into the unconscious through complexes by using word association tests. Jung wrote, 'modern psychology with its investigation of complexes has opened up a psychic taboo area riddled with hopes and fears', and complexes remain an unexplored taboo area of research. In the present study, we have investigated the influence of complexes on unconscious cognitive processing, in particular on implicit learning. We have found that complexes shown to disturb conscious cognitive processing in fact enhanced the attention of the subjects and their performance on an implicit learning task. These results suggest that complexes are not just abstractions, but have various actual influences on both conscious and unconscious processing.     

Infant behaviors influence mothers’ provision of responsive and directive behaviors

Mother–infant interactions are important to infant development because they are predictive of infants’ social, cognitive, and language development (0070 and 0150). Because maternal responsive and directive behaviors are associated with differential infant outcomes, it is important to investigate influences on mothers’ provision of responsive and directive behaviors. Yet, the dyadic interaction literature is predominantly unidirectional from maternal behavior to infant outcomes. Therefore, the current study examined infant initiating behaviors and consequent maternal responses in a sample of 26 13-month-old infants and their mothers, videotaped during 5 min of free-play. Findings revealed that infants produced a variety of initiatives, and that these different infant initiatives prompted differential patterns of maternal responsive versus directive behaviors. Further, results of analyses of divergent types of maternal directive behaviors – Responsive Directives, ReDirectives, and Intrusive Directives – also may help clarify major discrepancies in the current literature regarding the positive and negative effects of maternal directiveness.     

The influence of augmented feedback and prior learning on the acquisition of a new bimanual coordination pattern

The present research examined two variables regarding the acquisition of a new bimanual coordination pattern: the role of previous experience and the nature of augmented feedback. Two groups of participants acquired a new coordination pattern (135 degrees relative phase) following two sessions of practice of another novel pattern (90 degrees relative phase). Transfer of learning in these groups was compared to two groups that had not previously learned a new pattern, but were nevertheless influenced by coordination patterns that are intrinsic to the task of bimanual relative timing (in-phase, 0 degrees, and anti-phase, 180 degrees). The findings revealed that new learning overshadowed the influence of the intrinsic patterns. Learning was also greatly affected by augmented feedback: dynamic, on-line pursuit tracking information was more effective in transfer than static, terminal feedback. Implications of these findings regarding theoretical constructs in motor learning are discussed.     

Some experiments on perceptual learning of mirror-image acoustic patterns

It is well known that the formant transitions of stop consonants in CV and VC syllables are roughly the mirror image of each other in time. These formant motions reflect the acoustic correlates of the articulators as they move rapidly into and out of the period of stop closure. Although acoustically different, these formant transitions are correlated perceptually with similar phonetic segments. Earlier research of Klatt and Shattuck (1975) had suggested that mirror image acoustic patterns resembling formant transitions were not perceived as similar. However, mirror image patterns could still have some underlying similarity which might facilitate learning, recognition, and the establishment of perceptual constancy of phonetic segments across syllable positions. This paper reports the results of four experiments designed to study the perceptual similarity of mirror-image acoustic patterns resembling the formant transitions and steady-state segments of the CV and VC syllables /ba/, /da/, /ab/, and /ad/. Using a perceptual learning paradigm, we found that subjects could learn to assign mirror-image acoustic patterns to arbitrary response categories more consistently than they could do so with similar arrangements of the same patterns based on spectrotemporal commonalities. Subjects respond not only to the individual components or dimensions of these acoustic patterns, but also process entire patterns and make use of the patterns’ internal organization in learning to categorize them consistently according to different classification rules.     

Development and learning: a TASC-based perspective of the acquisition of perceptual-motor behaviors

The concepts of development and learning are discussed in terms of different theoretical orientations to the study of motor behavior. It is argued that although these concepts are commonly used to discuss various aspects of change across the life span, there is little agreement regarding the definition of these terms and even whether these are useful concepts for researchers studying change over time. A theoretical approach, the TASC-based approach is presented as an alternative account for examining change over time. The TASC label stands for a focus on particular tasks, adaptation and selection of behaviors as a function of constraints. This account is grounded in evolutionary theory and assumes that variability, selection, and adaptation are central to change over time within individuals. Emphasis is placed on the tasks individuals attempt to solve in achieving particular goals given the constraints of the local environment and the organism. An alternative manner to conceptualize the concepts of development and learning are presented within the TASC-based approach.     

Phonologically mediated priming of preexisting and new associations in young and older adults

In 2 experiments, the authors investigated phonologically mediated priming of preexisting and new associations in word retrieval. Young and older adults completed paired word stems with the first word that came to mind. Priming of preexisting associations occurred when word-stem pairs containing homophones (e.g., beech-s____) showed more completions with the target (e.g., sand) relative to unrelated pairs (e.g., batch-s____), with more priming for subordinate than for dominant homophones. Priming occurred for new associations independent of dominance such that word-stem pairs containing homophones (e.g., beech-l____ and beach-l____) were completed with the same word (e.g., laugh) more often than unrelated pairs (e.g., beech-l____ and batch-l____). No age differences in phonologically mediated priming were found for either type of association, suggesting age equivalence in the use of bottom-up phonological connections.