The accuracy of time-to-contact (TTC) judgments for single approaching objects is well researched, however, close to nothing is known about our ability to make simultaneous TTC judgments for two or more objects. Such complex judgments are required in many everyday situations, for instance when crossing a multi-lane street or when engaged in multi-player ball games. We used a prediction-motion p...

The authors describe ACT-R/perceptual-motor (ACT-R/PM), an integrated theory of cognition, perception, and action that consists of the ACT-R production system and a set of perceptual-motor modules. Each module (including cognition) is essentially serial, but modules run in parallel with one another. ACT-R/PM can model simple dual tasks such as the psychological refractory period (PRP), includin...

We give new examples of discrete Schrδdinger operators with potentials taking finitely many values that have purely singular continuous spectrum. If the hull X of the potential is strictly ergodic, then the existence of just one potential x in X for which the operator has no eigenvalues implies that there is a generic set in X for which the operator has purely singular continuous spectrum. A su...

Most studies using the psychological refractory period (PRP) design suggest that dual-task performance is limited by a central bottleneck. Because subjects are usually told to emphasize Task 1, however, the bottleneck might reflect a strategic choice rather than a structural limitation. To evaluate the possibility that central operations can proceed in parallel, albeit with capacity limitations...

The developmental period of a child has critical importance for learning and it is even more so in case of a disabled child. The earlier the disability is detected, the easier it is to effectively help the child both medically and educationally. The present paper is an attempt to define and describe developmental disability both as a concept and as a practical program of intervention. The main ...

1- introduction crop development is qualitative changes planned that led the plant to ripening. factors such as water available, nitrogen and photosynthetic materials are affected growth and development. under irrigated conditions expected that all of factors except climate elements be controlled. thus, only climate elements able to change of plant growth and development and under these conditi...

Uptake of cadmium into molar enamel and dentin from rats receiving cadmium in their drinking water was markedly elevated and proportional to the amount of cadmium in the drinking water. Post-developmental cadmium did not influence caries development or alter the cariostatic effectiveness of fluoridated drinking water. The data indicate that the absolute concentration of cadmium in teeth is not ...