Visual texture perception and Fourier analysis

The relationship between the Fourier spectra of visual textures (represented by four hypothetical visual channels sensitive to spatial frequencies) and the perceptual appearance of the textures was investigated. Thirty textures were synthesized by combining various spatial frequencies of different amplitudes. Twenty subjects grouped the textures into 2, 3, 4, and 5 groups based on the similarity of their appearance. The groupings were analyzed by means of linear discriminant analysis using the activity of the four channels as predictor variables. The groupings were also examined by multidimensional scaling, and the resulting stimulus configuration was canonically correlated with the channel activity. The results of both analyses indicate a strong relationship between the perceptual appearance of the textures and their Fourier spectra. These findings suport a multiple-channel spatial-frequency model of perception.     

Visual discrimination of texture

Julesz (1975) proposed a theory of texture discrimination, based on an order statistics principle, which states that no two textures can be perceptually discriminated if they have identical second-order statistics. The experiments reported here demonstrate that this principle is not adequate to predict visual texture discriminability. Both letter and dot micropatterns were used to create texture pairs that either differed or were identical with respect to secondorder statistics. The subject’s task was to decide which quadrant of an array contained a disparate texture. In Experiments 1, 2, and 3, when controlling for spatial overlap, texture pairs having identical second-order statistics were discriminated more quickly than similar texture pairs having different second-order statistics, in contradiction to the principle. Although a significant effect in the direction predicted by the order statistics principle was found in Experiment 4 for texture pairs created from the dot micropatterns, other factors, such as spatial overlap, border differences, and goodness of pattern, must also be considered in predicting texture discriminability.     

Attention to words in different modalities: Four-channel presentation with physical and semantic selection

Theoretical controversy surrounds the issue of whether central processing capacity is unitary and general or whether different types of processing capacity may be distinguished. Three bisensory experiments investigated the selection of words by physical and semantic attributes. It was found that recall was superior following bimodal (auditory and visual) rather than unimodal (auditory or visual) presentation. Furthermore, the difference between bimodal and unimodal recall was greater when the words were physically selected than when they were semantically selected. The results provide evidence that the availability of different types of processing capacity is dependent upon the mode of presentation of material and its required type of analysis.     

A SUPERVISORY STRATEGY TO IMPROVE WORK PERFORMANCE FOR LOWER FUNCTIONING RETARDED CLIENTS IN A SHELTERED WORKSHOP

A multiple component strategy was investigated for aiding staff responsible for supervising production of lower functioning retarded clients on contract tasks in an institution-based sheltered workshop. The strategy was assessed in a combined multi-element, multiple baseline across groups design with a reversal component. Production performance increased during the production supervisory strategy with all 16 clients, with the range of increase varying from a few percentage points to 150% of baseline production. Both the clients and staff (responsible for conducting the research) preferred working under experimental conditions rather than under baseline conditions which approximated those found in “typical” sheltered workshops.     

Cognitive task effects on hemispheric blood flow in humans: Evidence for individual differences in hemispheric activation

Evidence from two indirect measures of hemispheric activity, EEG α and conjugate lateral eye movements, has pointed to the existence of individual differences in hemispheric activation. Results from a more direct indicator of hemispheric activity, regional cerebral blood flow as measured by the ¹³³Xe inhalation method, show that such individual differences can be detected in the distribution of blood in the two hemispheres and that the amount of increase in blood flow in the right relative to the left hemisphere is correlated with performance on a spatial task. These results corroborate and extend the findings from the EEG and eye movement studies and suggest that the dimension of individual differences in hemispheric activation may exert significant influence on cognitive performance and on problem-solving strategies.     

PSYCHOLOGY AND SOCIETY IN ISRAEL*

The development of psychology in Israel is presented as a reflection of its society's aims and needs. Until the early 50′s, the major orientation of Israel's population was geared towards achieving national and ideological goals. Scientific as well as applied psychology was not perceived as being able to fulfill or even being in line with these goals. However, starting from the early 50′s, Israel's ideological orientation as well as its practical needs changed dramatically. Mass immigration, housing problems, ethnicity, urbanization, industrialization, the emergence of underprivileged groups and a more individualistically oriented ideology raised new problems and strongly required the services of psychology. This paper tries to show how different branches of psychology - scientific as well as applied ones - developed as a direct function of the country's social needs and problems and its search for appropriate ways of dealing with them.     

TEACHING THE HANDICAPPED TO EAT IN PUBLIC PLACES: ACQUISITION,GENERALIZATION AND MAINTENANCE OF RESTAURANT SKILLS

This study examined classroom-based instruction in restauranting skills for handicapped persons. Three male students were taught each of four skill components in sequential order: locating, ordering, paying, and eating and exiting. Training was implemented in a multiple baseline design across subjects and consisted of modeling and role playing in conjunction with photo slide sequences and a simulated ordering counter. The use of a menu containing general item classes and a finger matching procedure for identifying errors in the delivery of change greatly reduced the reading and math skills necessary to enter and complete the program. Periodic probes were conducted in a McDonald's restaurant prior to, during, and up to one-year following the termination of training. In addition, two probes (overt and covert observation) were conducted in a Burger King restaurant to assess further generalization to a location different from the one depicted throughout training. Results showed that students' performance on restaurant probes improved as a result of training, generalized to novel settings, maintained over an extended period of time, and was comparable to that of a normative sample of nonretarded persons.