Task Decomposition Through Competition in a Modular Connectionist Architecture: The What and Where Vision Tasks

A novel modular connectionist architecture is presented in which the networks composing the architecture compete to learn the training patterns. An outcome of the competition is that different networks learn different training patterns and, thus, learn to compute different functions. The architecture performs task decomposition in the sense that it learns to partition a task into two or more functionally independent tasks and allocates distinct networks to learn each task. In addition, the architecture tends to allocate to each task the network whose topology is most appropriate to that task. The architecture's performance on “what” and “where” vision tasks is presented and compared with the performance of two multilayer networks. Finally, it is noted that function decomposition is an underconstrained problem, and, thus, different modular architectures may decompose a function in different ways. A desirable decomposition can be achieved if the architecture is suitably restricted in the types of functions that it can compute. Finding appropriate restrictions is possible through the application of domain knowledge. A strength of the modular architecture is that its structure is well suited for incorporating domain knowledge.     

Ambulatory blood pressure and heart rate in healthy male paramedics during a workday and a nonworkday.

Compared ambulatory blood pressure (BP) and heart rate (HR) in 30 paramedics during a 24-hr workday and a 24-hr nonworkday. During the 24-hr period as a whole, there were no BP differences between the workday and the nonworkday, but HR was higher during the nonworkday than during the workday. Systolic BP (SBP) recorded in the ambulance on the workday was elevated 9.8 mm Hg, compared to SBP recorded in a car on the nonworkday; it was also 7.2 mm Hg higher at the scene of an accident and at the hospital than during nonworkday activities. Ratings of moods in diaries indicated that paramedics felt more unhappiness, stress, and sadness and less feelings of pleasantness at work than at home. Rather than being elevated for the entire 24-hr period, work BP seemed to reflect the relatively high stress associated with specific situations in the work of a paramedic.     

Use of preferential inspection to define the viewing sphere and characteristic views of an arbitrary machined tool part.

Measurements were made of the way human subjects visually inspected an idealized machined tool part (a 'widget') while learning the three-dimensional shape of the object. Subjects were free to rotate the object about any axis. Inspection was not evenly distributed across all views. Subjects focused on views where the faces of the object were orthogonal to the line of sight and the edges of the object were aligned parallel or at right angles to the gravitational axis. These 'face' or 'plan' views were also the easiest for subjects to bring to mind in a mental imagery task. By contrast, when subjects were instructed to imagine the views displaying the most structural information they visualized views lying midway between face views.     

GUATEMALAN, FILIPINO, AND U.S. ADOLESCENTS'IMAGES OF WOMEN AS OFFICE WORKERS AND HOMEMAKERS

Although adolescents of different countries often draw pictures of the ideal woman cooking or working in an office, the meaning of the images may vary cross-culturally. In the present study, 88 adolescents from the Philippines, the U.S.A., and Guatemala interpreted drawings by their same-nationality peers. Interpreters from all three countries described the woman working in an office as hardworking and the woman cooking as a mother cooking for her family. In addition, Filipino adolescents wrote themes of contentment and organization, Guatemalan adolescents wrote themes of betterment, family, and hope, and U.S.A. adolescents wrote themes of contentment and niceness. Similar images of women's roles may have different meanings for adolescents of different cultures, and the use of emic approaches can provide psychological researchers with increased understanding of complex social phenomena.     

Book reviews

Hall, G. (1991). Perceptual and associative leaning. Oxfod: Clarendon Press. Pp. xi + 300. ISBN 0-19-8524182-0. £35.00.

Rahmann, H., & Rahmann, M. (1992). The neurobilogical basis of memoy and behavior. New York: Springe Verlag. Pp. 292. ISBN 3-540-97545-4. £53.00.

Iversen, I.H., & Lattal, K.A. (Eds.). (1991). Experimental analysis of behavior, arts 1 and 2. Techniques in the behavioral and neural sciences, volume 6 (series editor: J.P Huston). Amstedam: Elsevier. Pp. 724. ISBN 0-444-8932-2. £50.00 (paperback).

Baudry, M., & Davis, J.L. (Eds.) (1991). Long-tem potentiation: A debate of current issues. Cambridge, Ma & London, England: MIT Press. Pp. xxii + 454. ISBN 0-262-02330-x. £62.95 (Hb).

The Biological Council Animal Reseach and Welfare Panel (1992). Guidelines on the handling and training of laboatory animals. Univer-sities Federation for Animal Welfare. Pp. ISBN 0-900767-77-4. £2.50.     

Differences in performance of young and old monkeys on a visuospatial memory task

Two groups of stumptailed macaques (Macaca arctoides) were compared in terms of performance on a visuospatial working memory task involving repeated presentations of an array of 15 doors, each of which concealed one food reward at the start of a session. Rewards obtained by the subject were not replaced. Errors were defined as responses to doors previously pushed open during the session. Both groups generally obtained all rewards and showed improved performance across sessions, but old monkeys consistently made more errors than young ones, especially in the latter half of a given session. Further, old monkeys were less diverse in the errors they made, indicating different response strategies by the two groups.     

Latent inhibition, context specificity, and context familiarity

In two appetitive licking experiments, thirsty rats were pre-exposed to two stimuli prior to conditioning sessions in which one or both of these stimuli were paired with water. Consistent with other results, latent inhibition was disrupted when conditioning took place in a context different from that in which stimulus pre-exposure had occurred. But in animals given prior exposure to the context of stimulus pre-exposure before the start of stimulus pre-exposure, substantial and equivalent latent inhibition was evident whether or not there was a change of context between stimulus pre-exposure and conditioning. These results are discussed in terms of current theories of latent inhibition.