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.     

Ebbinghaus illusions: Size contrast or contour interaction phenomena?

Forty-eight graduate and undergraduate students between 17 and 30 years of age judged the size of the central circle in Ebbinghaus figures presented under either simultaneous or successive viewing conditions. Successive presentation eliminated the illusion produced by the normally overestimated figure and diminished that produced by the underestimated figure. Under simultaneous viewing conditions, increasing the number of surrounding circles reduced the magnitude of the reversed illusion produced by the normally overestimated figure but had no effect on the illusion produced by the underestimated figure. Under successive viewing conditions, increasing the number of surrounding circles had no effect on the magnitude of illusion produced by the normally overestimated figure but increased the illusion produced by the underestimated figure. These data were interpreted as inconsistent with a size contrast explanation of the Ebbinghaus illusions and suggested that these illusions may be produced by a contour interaction process.     

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.     

A real-time satellite system based on UNIX

One solution to the difficulty of running real-time applications under UNIX is to develop the application programs on an available UNIX system and execute them on a dedicated satellite processor. This combines the advantages of a powerful timesharing operating system with the real-time capabilities of a single-process system. PARASITE, a real-time satellite system, provides tools for developing the application program on the host and executing it on a satellite. A host utility serves to invoke the standard UNIX C compiler and link its output with the PARASITE library. The PARASITE library consists of routines that mimic the standard library and routines that read and write the real-time peripherals. PARASITE currently supports digital inputs and outputs, asynchronous serial-line interfaces, program-mable real-time clocks, and analog-to-digital and digital-to-analog converters. Another PARA-SITE utility downloads the object code of the user program and PARASITE support code into the satellite, where it runs independently. Once the application routine is executing on the satellite, it controls the satellite processor at all times and is continuously available for servicing hardware-generated interrupts. When a real-time peripheral interrupt routine is invoked by a hardware interrupt, it sends a software signal to the user program, in addition to processing the interrupt. This allows the user program to perform additional tasks that are specific to the application. All data to be permanently stored must be transferred to the host. Since the satellite has no direct access to the resources of the host, a process running on the host receives the data and manages files. PARASITE provides packet driver routines on both the host and the satellite, which together handle the data transmission protocol.     

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.     

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.