Detectability and choice during visual search: joint effects of sequential priming and discriminability

Pigeons searched for symbolic targets among heterogeneous distractor items displayed on a video monitor. Phase 1 varied target identity and overall display size, thus establishing differential discriminabilities of three target symbols. Phase 2 varied the relative probability of these targets within sessions. The findings showed that reaction time was lower not only when targets were more discriminable, but also when they were relatively frequent; these effects did not depend on the discriminability of the less frequent targets. Phase 3 was similar in design but provided occasional choice trials on which two targets appeared. The birds were more likely to respond to the more frequent target on such trials only if it was also the most discriminable. The data are not consistent with certain predictions from Guilford and Dawkins’ (1987) reinterpretation of effects attributed to search images. The data indicate that detection and choice are modified jointly by priming-induced expectancies and stimulus-driven perceptual processes.     

The elaboration theory of instruction: A model for sequencing and synthesizing instruction

This paper describes a novel instructional model for sequencing, syntheizing, and summarizing subject-matter content. The importance of such models is discussed, along with the need for a significant change in the role of subject-matter structure in instruction. A zoom-lens analogy is presented to facilitate an understanding of the elaboration model of instruction. Some basic concepts and principles upon which the model is based are described. The basic unvarying components of the elaboration model are described. And finally, some variations in the model for different kinds of goals are described. The elaboration model follows a general-to-detailed pattern of sequencing, as opposed to the hierarchically based sequences derived from Gagné-type task analyses.Many of the ideas described in this paper were developed under two projeets, one funded by Brigham Young University in Provo, Utah, and the other by the Navy Personnel Research and Development Center in San Diego, California; however, the ideas expressed do not necessarily constitute the opinions of the funding institutions.     

Cost-effectiveness of audiovisual media in higher education

In general, economists are engaged in optimizing the ratio between benefits and costs. The so-called cost-effectiveness approach is oriented towards producing specified effects at the lowest costs. How this may be done for audiovisual media in higher education is shown in two steps. First, the function-identifying stage, then the cost-analysis stage. The cost-structures of seven methods of delivering instructional television are then compared. Finally, some reasons are given for why cost-effectiveness considerations are still rarely applied in educational decision-making. Structural measures to remedy this state of affairs are proposed.Detailed cost calculations which support the ideas put forward in this article were to have been included in an appendix: this can be obtained from the author.     

Pigeons see the Ponzo illusion

Three experiments were performed to address factors contributing to the Ponzo illusion. In Experiment 1, pigeons learned to peck at the longer of two bars in varying line contexts. When these lines converged, the birds had difficulty in learning several patterns in which a Ponzo illusion would reduce the perceived difference. In Experiment 2, the subjects chose one response if a stimulus bar was longer than a predetermined length and a second response for shorter bars. The subjects were more likely to choose “long” as the stimulus bar approached the apex of converging lines. These results suggested that pigeons experience the Ponzo illusion. In Experiment 3, the effects of contexts that did and did not form a texture gradient were compared. The magnitude of the illusion did not differ according to context lines. This result failed to support a perspective theory of the Ponzo illusion.     

Use of Live Supervision in Counselor Preparation

This study investigates the use of live supervision in counselor preparation programs. The perceived impact of live supervision on program management and student development are also considered.