Mechanisms for seeing transparency-from-motion and orientation-from-motion

Structure-from-motion (SFM) perception is hypothesised to be mediated by units that sense the near-far relationships in transparency-from-motion (TFM) and orientation-from-motion (OFM). The frequency of subjective reversals during observation of ambiguous SFM displays is considerably decreased when either the direction of rotation or the surface orientation is oscillated during the inspection. Such manipulations impede adaptation of units selectively sensitive to TFM and OFM. The results show that both OFM and TFM units are direction-selective, and that the reversal rate is unaffected by reducing TFM to zero; and support the view that depth order, when both TFM and OFM are present, is estimated by common neural units.     

Task demands and limb apraxia in stroke

The present study was designed to examine the frequency and severity of apraxia in patients with left- or right-hemisphere stroke in both pantomime and imitation conditions and to compare the frequency of apraxia in each stroke group across the three patterns of apraxia described in Roy's model (Roy, 1996). Ninety-nine stroke patients and 15 age-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gestural performance was quantified as accuracy on five performance dimensions; a composite score, an arithmetic combination of the five performance dimensions, was used as an index of the overall accuracy. Analyses revealed a comparable proportion of patients in each stroke group were classified as apraxic in the imitation condition, but a higher proportion of left stroke patients were apraxic in the pantomime condition. The severity of apraxia in each stroke group and the performance dimensions affected were, however, comparable. Analyses of the patterns of apraxia (pantomime alone, imitation alone or apraxia in both conditions) revealed a higher frequency of apraxia in both stroke groups for the pattern reflecting apraxia in both conditions, indicating that a disruption at the movement execution stage of gesture performance was most common.     

Dimensional complexity and power spectral measures of the EEG during functional versus predicative problem solving

Electroencephalograms were recorded in 22 men while solving tasks of visual-pattern completion and during mental relaxation. They were primed (by foregoing trials) to solve these tasks either in a predicative or functional mode of thinking. Predicative thinking required that in order to complete the pattern the subject had to get involved with the logic of the static structure of the pattern and therefore had to recognize the recurrence of certain features of the elements (e.g., shape, color, and size). Functional thinking required involvement in a dynamic reading of the logic of the pattern and therefore to search for operations and actions to be performed on the pattern elements (e.g., pushing, mirroring, and rotating). The EEG complexity during predicative thinking decreased in comparison to functional thinking and mental relaxation, with this reduction being most pronounced over the right parietal cortex. A reduction in dimensional complexity during functional thinking as compared to mental relaxation, which was concentrated over the left central cortex, although significant, was less clear. The reduced EEG complexity during predicative thought, dominant over the right hemisphere, could reflect increased competitive inhibition among respective cortical neuron assemblies in association with the visual analysis of static element features, converging upon those predicates relevant for the solution.     

Establishing operations, cognition, and emotion

In this paper we argue that behavior analysts have tended to neglect the study of important aspects of complex human behavior, including cognition and emotion. This relative neglect has been costly in terms of mainstream psychology's perception of the field of behavior analysis and in terms of our ability to provide a more thorough account of human behavior. Observations and findings from the clinical context are offered as examples of behavior that are not readily explained by the three-term contingency, and we argue that an adequate account of these behaviors must include principles derived from recent behavior-analytic work, in particular a better understanding of the short- and long-term effects of establishing operations. The concept of the establishing operation and its implications for understanding complex human behavior are discussed.     

When did Mrs Thatcher resign? The effects of ageing on the dating of public events

Two experiments investigated whether, in light of the commonly reported phenomenon of subjective time acceleration with age, there would be an effect of age on the dating of public events. In the first experiment covering the past seven years there was the suggestion of a decrease in forward telescoping with age, and in the second covering the period from 1977-89 this trend was continued, with the over-60s group now showing a tendency to date events too distantly. This effect is uncommon in dating studies and may offer evidence for the existence of time acceleration. An additional finding was that adults in the age range 35-50 years showed greater accuracy in dating events than did university students and adults over the age of 60.