Evaluation of a dynamical model of speech perception

Previous work (Tuller, Case, Ding, & Kelso, 1994) has revealed signature properties of nonlinear dynamical systems in how people categorize speech sounds. The data were modeled by using a twowell potential function that deformed with stimulus properties and was sensitive to context. Here we evaluate one prediction of the model—namely, that the rate of change of the potential’s slope should increase when the category is repeatedly perceived. Judged goodness of category membership was used as an index of the slope of the potential. Stimuli from a “say”-“stay” continuum were presented with gap duration changing sequentially throughout the range from 0 to 76 to 0 msec, or from 76 to 0 to 76 msec. Subjects identified each token as either “say” or “stay” and rated how good an exemplar it was of the identified category. As predicted, the same physical stimulus presented at the end of a sequence was judged a better exemplar of the category than was the identical stimulus presented at the beginning of the sequence. In contrast, stimuli presented twice near the middle of a sequence with few (or no) stimuli between them, as well as stimuli presented with an intervening random set, showed no such differences. These results confirm the hypothesis of a context-sensitive dynamical representation underlying speech.     

The Leaning Tower of Pisa effect: an illusion mediated by colour, brightness, and motion

We report a novel, easily observed, and extraordinarily striking optical illusion mediated by interactions of colour, brightness, form, and motion perception--the Leaning Tower of Pisa (LTOP) illusion. Under some circumstances, the perception of orientation of coloured forms is radically altered by rotary movement. We demonstrate that this kinetic effect--easily reproduced with a common record turntable--is optimised by particular colour and brightness differences between foreground and background with an illusory tilt of 8 degrees and more. The described illusions can be easily studied at home by downloading the colour figures from www.perceptionweb.com/perc1000/ditzinger, printing them on a common colour printer and placing them on a rotating record turntable.     

To Switch or Not to Switch: Recruitment of Degrees of Freedom Stabilizes Biological Coordination

Recruitment and suppression processes were studied in the swinging-pendulum paradigm (cf. P. N. Kugler & M. T. Turvey, 1987). The authors pursued the hypothesis that active recruitment of previously unmeasured degrees of freedom serves to stabilize an antiphase bimanual coordination pattern and thereby obviates the need for pattern switching from an antiphase to an in-phase coordination pattern, a key prediction of the H. Haken, J. A. S. Kelso, and H. Bunz (1985) model. In Experiment 1, 7 subjects swung single hand-held pendulums in time with an auditory metronome whose frequency increased. Pendulum motion changed from planar (2D) to elliptical (3D), and forearm motion (produced by elbow flexion-extension) was recruited with increasing movement rate for cycling frequencies typically above the pendulum's eigenfrequency. In Experiment 2, 7 subjects swung paired pendulums in either an in-phase or an antiphase coordinative mode as movement rate was increased. With the systematic increase in movement rate, the authors attempted to induce transitions from the antiphase to the in-phase coordinative pattern, with loss of stability the key mechanism of pattern change. Transitions from the antiphase to the in-phase coordinative mode were not observed. Pattern stability, as defined by the variability of the phase relation between the pendulums, was affected only a little by increasing movement rate. As in the single-pendulum case, pendulum motion changed from planar to elliptical, and forearm motion was recruited with increasing cycling frequency. Those results reveal a richer dynamics than previously observed in the pendulum paradigm and support the hypothesis that recruitment processes stabilize coordination in biomechanically redundant systems, thereby reducing the need for pattern switching.     

Activating Basic Category Exemplars in Sentence Contexts: A Dynamical Account

This paper examines the influence of context on the processing of category names embedded in sentences. The investigation focuses on the nature of information available immediately after such a word is heard as well as on the dynamics of adaptation to context. An on-line method (Cross Modal Lexical Priming) was used to trace how this process unfolds in time. We found that the information available immediately after a category word is presented is not altered by the sentence context in which the word is immersed. Rather, the structure of availability of particular exemplars of the category resembles the typicality structure of a conceptual representation. The adaptation to context occurs later (between 300 and 450 ms after the category word) and takes the form of a rapid reorganization of the structure rather than a gradual activation of a contextually relevant exemplar. We claim that such data is best accounted for in a dynamical framework, where a coherent global structure emerges through locally guided self-organization.     

A preliminary evaluation of two behavioral skills training procedures for teaching abduction-prevention skills to schoolchildren

Although child abduction is a low-rate event, it presents a serious threat to the safety of children. The victims of child abduction face the threat of physical and emotional injury, sexual abuse, and death. Previous research has shown that behavioral skills training (BST) is effective in teaching children abduction-prevention skills, although not all children learn the skills. This study compared BST only to BST with an added in situ training component to teach abduction-prevention skills in a small-group format to schoolchildren. Results showed that both programs were effective in teaching abduction-prevention skills. In addition, the scores for the group that received in situ training were significantly higher than scores for the group that received BST alone at the 3-month follow-up assessment.     

The excitator as a minimal model for the coordination dynamics of discrete and rhythmic movement generation

The authors identify a class of excitable two-dimensional model systems, the excitators, that provide an entry point to the understanding of the mechanisms of discrete and rhythmic movement generation and a variety of related phenomena, such as false starts and the geometry of phase space trajectories. The starting point of their analysis is the topological properties of the phase flow. In particular, the phenomenon of false starts provides a characteristic structural condition for the phase flow, the separatrix, which partitions the phase space. Threshold phenomena, which are characteristic of excitable systems, as well as stable and unstable fixed points and periodic orbits, are discussed. Stable manifolds in the proximity of fixed points, resulting in an overshoot and a slow return phase after movement execution, are predicted in the analysis. To investigate coordination phenomena, the authors discuss the effects of two types of couplings, the sigmoidal coupling and a truncated version thereof, known as the Haken-Kelso-Bunz (HKB) coupling. They show analytically and numerically that the sigmoidal coupling leads to convergence phenomena in phase space, whereas the HKB coupling displays convergent as well as divergent behaviors. The authors suggest a specific representation of the excitator that allows the quantification of the predictions.     

Resilience Among Women with HIV: Impact of Silencing the Self and Socioeconomic Factors

In the U.S., women account for over a quarter of the approximately 50,000 annual new HIV diagnoses and face intersecting and ubiquitous adversities including gender inequities, sexism, poverty, violence, and limited access to quality education and employment. Women are also subjected to prescribed gender roles such as silencing their needs in interpersonal relationships, which may lessen their ability to be resilient and function adaptively following adversity. Previous studies have often highlighted the struggles encountered by women with HIV without focusing on their strengths. The present cross-sectional study investigated the relationships of silencing the self and socioeconomic factors (education, employment, and income) with resilience in a sample of women with HIV. The sample consisted of 85 women with HIV, diverse ethnic/racial groups, aged 24–65 enrolled at the Chicago site of the Women’s Interagency HIV Study in the midwestern region of the United States. Measures included the Connor-Davidson Resilience Scale -10 item and the Silencing the Self Scale (STSS). Participants showed high levels of resilience. Women with lower scores on the STSS (lower self-silencing) reported significantly higher resilience compared to women with higher STSS scores. Although employment significantly related to higher resilience, silencing the self tended to predict resilience over and above the contributions of employment, income, and education. Results suggest that intervention and prevention efforts aimed at decreasing silencing the self and increasing employment opportunities may improve resilience.