The effect of redundant stimulus elements on visual discrimination as a function of element heterogeneity,equal discriminability,and position uncertainty

Garner and Lee (1962) showed no gain in visual discrimination accuracy with addition of redundant stimulus elements. Eriksen and Lappin (1965) showed a substantial gain. One experiment reported here indicates that the discrepancy is not due to the fact that the earlier experiment used heterogeneous stimulus elements. A second experiment indicated that the gain in discrimination accuracy does occur when the additional stimulus elements have the same discriminability as the original elements. It also showed that position uncertainty itself has no effect on the gain with redundant elements, but is a convenient procedural device for maintaining fixation and thus equal element discriminability. Three models of perceptual independence fit the data.     

Reaction time as a function of stimulus uncertainty on a single trial

In a discrete choice-reaction-time experiment, reaction times were measured between the onset of a light and the start of S’s pencil toward that light. The reaction time of unpracticed Ss, not aware that their first “practice” trial was being measured, increased as a linear function of stimulus uncertainty. Since this occurred without any prior experience, the effect must have been due to S’s set or expectancy regarding the nature of the future task, formed while the instructions for the task were being given.     

Illusion magnitude as a function of visual field exposure

Forty-eight right-handed subjects divided into four groups, each consisting of six males and six females, were employed in an investigation of cerebral hemispheric influence on the perception of tachistoscopically presented simultaneous and successive versions of the Mueller-Lyer figure. The simultaneous version exposed in the left visual field resulted in a larger effect than did right visual field exposures. The successive version exposed in the right visual field resulted in a larger illusion magnitude than it did in the left visual field. The magnitude of visual field differences in response to the successive version was greater than visual field differences found in response to the simultaneous version     

Performance of the vertical position in synchronized swimming as a function of skill, proprioceptive and visual feedback

This experiment assessed the efficacy of proprioceptive and visual information for the performance of "vertical position" by synchronized swimmers. Three skill groups of 5 senior, 5 intermediate, and 5 novice synchronized swimmers performed 40 vertical positions under four conditions. The conditions were: self-initiated with and without vision, and following experimenter perturbation, with and without vision. The dependent measure was degrees of error from true vertical. Analysis indicated that either proprioception or proprioception and vision may be used in performing vertical positions. A significant main effect was found among skill groups.     

Intentional and incidental visual memory as a function of cognitive level and color of the stimulus

Performance of two groups of youngsters, educable mentally retarded (CA 15-5; MA 11-4; IQ 74.3) and those of average ability (CA 10-5; MA 11-3; IQ 109.1) was compared for intentional and incidental visual memory as a function of cognitive level and color of the stimulus. Nonretarded subjects performed significantly better than the retarded ones of equal MA. Both groups performed better with a color than black-white card, and both groups did better on the tasks involving intentional rather than incidental memory.     

Differential encoding as a function of semantic polarity and form of visual stimulus presentation

The present study investigated the saliency of form of visual stimulus presentation (printed word or picture) and of the semantic evaluative dimension (positive or negative) as encoding attributes for fifth-grade children. Three short-term memory trials within one visual form of presentation or one pole of the evaluative dimension were followed by a fourth short-term memory trial on which the stimulus material was shifted on one or both attributes (experimentals) or held constant (controls). The recall of the experimental groups consistently exceeded that of the control groups on the shift trial, providing evidence for a release from proaetive inhibition and implying the saliency of both the form of visual stimulus presentation and the evaluative polarity of the stimulus concepts as encoding dimensions.