The coding of constrained and preselected movement distance: Same-limb versus switched-limb reproduction

Three experiments were conducted to investigate the codes subserving the retention of movement extent information. Each experiment compared preselected and constrained movements in two independent movement tasks: same-limb reproduction and switched-limb reproduction. When movement direction was the same for both criterion and reproduction movements (experiment 1), same-limb reproduction was more accurate than switched-limb performance. With movement direction altered, however, switched-limb reproduction was equal to same-limb reproduction (experiment 2). These results were confirmed in experiment 3 which manipulated both movement direction and reproduction limb in a within-subject design. Furthermore, while preselected reproduction was superior to constrained reproduction in all three experiments, the two groups were not differentially affected by either the movement task or direction variables. The overall findings were interpreted as providing support for a multiple-cue memorial representation of movement extent and the notion of coding flexibility.     

Evidence for phonetic processing of cues to place of articulation: Perceived manner affects perceived place

Using stimuli that could be labeled either as stops [b,d] or as fricatives [f,v,θ,ð], we found that, for a given acoustic stimulus, perceived place of articulation was dependent on perceived manner. This effect appeared for modified natural syllables with a free-identification task and for a synthetic transition continuum with a forced-choice identification task. Since perceived place could be changed by changing manner labels with no change in the acoustic stimulus, it follows that the processing of the place feature depends on the value the listener assigns to the manner feature rather than directly on any of the acoustic cues to manner. We interpret these results as evidence that the identification of place of articulation involves phonetic processing and could not be purely auditor     

Case study: Effects of naltrexone and sibis on self-injury

The present case study was an effort to determine the relative effectiveness of two variant treatment modalities, and to provide an exploratory study of the hypothesis that therapy with naltrexone might increase the effectiveness of an aversive stimulus in controlling self-injury. Data are presented for a man who was treated for severe self-injury with the Self-Injurious Behavior Inhibiting System (SIBIS) and naltrexone, conducted under open-trial conditions utilizing fixed doses of 50 mg, 75 mg, and 100 mg per day. The effects of naltrexone on SIB were evaluated alone and paired with SIBIS. When used alone, lower dosages of naltrexone produced moderate decrements in self-injury. However, the rate of SIB increased in a dose-dependent manner when naltrexone was paired with SIBIS. The data also suggested that naltrexone may have caused a generalized blunting of both positive and negative affect.     

Physiological reactivity to stressors in irritable bowel syndrome patients, inflammatory bowel disease patients and non-patient controls.

Irritable Bowel Syndrome (IBS) patients were compared with Inflammatory Bowel Disease (IBD) patients and non-patient controls on four separate physiological measures (heart rate, finger-tip temperature, skin resistance level, and forehead EMG) for their physical reactivity to 'laboratory stressors'. It was predicted that the IBS patients would respond to these stressors with more physiological reactivity than the two other groups. There were initial basal differences among the groups on heart rate and finger-tip temperature: in general, the IBS patients had lower basal heart rates and the non-patient controls had lower finger-tip temperatures. These findings are contrary to the previous body of literature regarding possible sympathetic nervous system (SNS) arousal states in the IBS patient. The results also indicated IBS patients were not significantly different than the IBD patients or the non-patient controls in their reactivity to stressors. Previous literature has suggested that IBS in their reactivity to stressors. Previous literature has suggested that IBS patients have an enhanced SNS arousal or an SNS mediated reactivity to environmental stressors, our current study has not found these results.     

Applications of the PLATO computer system to research in social psychology

The use of the PLATO CAI system in psychological research is discussed. This discussion covers the use of the PLATO system for research in personal space, attribution, person perception, and group decision making. The aspects of the PLATO system that facilitate research in each of these topic areas are discussed in detail. Further modifications of the PLATO system that would enhance its applicability to psychological research are also discussed.     

Energetic Cost and Stability During Human Walking at the Preferred Stride Velocity

The possibility that preferred modes of locomotion emerge from dynamical and optimality constraints and the energetic and dynamical constraints on preferred and predicted walking frequency are explored in this article. Participants were required to walk on a treadmill at their preferred frequency, at a frequency predicted as the resonance of a hybrid pendulum-spring model of the legs, and at frequencies +/-15%, +/-25%, +/-35% of the predicted frequency. Walking at the preferred and predicted frequencies resulted in minimal metabolic costs and maximal stability of the head and joint actions. Mechanical energy conservation was constant across conditions. The head was more stable than the joints. The joints appeared to be in service of the head in maintaining a stable trajectory. The major findings of this study suggest a complementary relationship between energetic (physiological) and stability constraints in the adoption of a preferred frequency of walking. Multiple subsystems may be involved in constraining observed macroscopic behavior in intact biological systems. The approach and results of the study imply that a useful tack in understanding how dynamical control structures arise is to study the potential criteria that serve to act as constraints on skilled movement patterns in unimpaired and impaired populations.