The SNS response decrement obtained by Mefferd and Wieland (1965) when a congitive task was imposed during a painful stimulus was reproduced with 15 Ss under conditions involving minimal motor activity. The results support the conclusion that cognitive activity/»er se was the major determinant of the decrement.After a decrease caused by alerting the S for the first passage no further significant changes in BSR occurred. The mean GSR (sum of transient decreases in resistance adjusted to a per minute basis) increased from .99 kilohms during the baseline period to 3.78 kilohms during the passage alone (two-tailed t test, p < 0.01) and to 6.60 kilohms during the cold pressor. Immediately after the passage was imposed on the cold pressor the GSR decreased, and the mean for the period was 4.00 kilohms-a significant decrease from the cold pressor period (p < 0.01, two-tailed t test). These results are the same as those obtained in our earlier study. They support the conclusion that the key determinant of the response decrement was not the motor activity of work association, and demonstrate that the results can be generalized to a larger population.

Sympathetic activity (SA) was reduced when a cognitive task was imposed during an ongoing response to cold pressor. However, this reduction effect was not obtained when CP was imposed 40‐sec after the onset of a cognitive task. Rather the response level appeared to be about that which would have been obtained from cold pressor alone. These results suggest that the reduction found in the former situation is not the result of distraction due to cognitive activity per se, as we had previously proposed, but it is the initial SA resulting from presentation of the cognitive task that causes the interaction. This suggests that the competition occurs at a level below that of cognition.

The nature of perspective reversal was examined using among other techniques a previously undescribed movement illusion specific to the non-veridical perception of actual depth. The apparent movement of the illusion proved to be veridical parallax movement displaced spatially. Apparent changes in direction of rotation and apparent oscillation were shown to be consequences of perspective. Objects seen in reversed perspective illustrated spectacularly the size-distance invariance. Detailed analysis revealed that depth perception per se is veridical, and only the apparent relocations of parts are involved in perspective reversal. When a perspective reverses, O misperceives the location of the near and far parts of the object, but those parts “reverse” about the veridical center in situ and on a strictly 1:1 depth basis. Perspective changes occur only at a plane perpendicular to O in the depth dimension—never in the horizontal-vertical plane. Parts of a single figure may reverse independently of others, thereby forming a separate perceptual unit, the configuration of which is determined by O‘s position rather than by properties of the stimulus. More complex figures (e.g., a rectangular prism composed of three cubes), may be perceived as an entire Gestalt, or as various smaller independent units each reversing perspective independently as verified by the movement illusion. The analysis of the nature of perspective reversal suggests that depth perception is composed of at least two processes: first, the perception of absolute depth, and second, the spatial ordering of objects or points on objects. The first process seems not to be related to perspective reversal, but the second seems to be implicated as the critical one. The depth dimension necessarily is represented nonveridically as a flat projection on the retina, while those parts of the visual field that are perpendicular to O are represented veridically. When O “reconstructs” the depth dimension from this flat retinal image (whether the depth is real or only apparent in the stimulus), depending on how he interprets the order of the corresponding parts, he will perceive the object in true or false perspective.

Uninstructed subjects choose to view, in sharp focus where possible, projected visual images in preference to various simpler auditory and visual stimuli (e.g., buzzers of flashing lights). The rate of responding on the lever rapidly increased above the operant level (projector inoperative) even though the stimuli were nonsense syllables. When focusing also was made contingent on responses, the subjects promptly started sharpening the focus of legible but blurred nonsense syllables. When the visual material was colored landscape scenes, the rates of slide-changing generally decreased, because of increased viewing time relative to the nonsense syllables, at the same time that the latencies of focusing decreased. Both the sharpness of focus and the total time spent with the image in sharp focus increased greatly with the colored slides, establishing that the subjects were under control of the stimulus events. Extinction of both responses occurred very rapidly when the controls became inoperative.

Galvanic skin responses (GSRs) were measured on 12 male Ss under four conditions: rest, reaction time measurements, a cold pressor, and a combination of cold pressor and reaction time measurements. Both reaction time measurements alone and cold pressor alone caused increased sympathetic activity, but when the former was combined with cold pressor the ongoing autonomic activity was depressed.