Perceived Depth in the ‘Sieve Effect’ and Exclusive Binocular Rivalry

An impression of a surface seen through holes is created when one fuses dichoptic pairs of discs, with one member of each pair black and the other member white. This is referred to as the ‘sieve effect’. The stimulus contains no positional disparities. Howard (1995, Perception24 67–74) noted qualitatively that the sieve effect occurs when the rivalrous regions are within the range of sizes, contrasts, and relative sizes where exclusive rivalry occurs, rather than binocular lustre, stimulus combination, or dominant rivalry. This suggests that perceived depth in the sieve effect should be at a maximum when exclusive rivalry is most prominent. We used a disparity depth probe to measure the magnitude of perceived depth in the sieve effect as a function of the sizes, contrasts, and relative sizes of the rivalrous regions. We also measured the rate of exclusive rivalry of the same stimuli under the same conditions. Perceived depth and the rate of exclusive rivalry were affected in the same way by each of the three variables. Furthermore, perceived depth and the rate of exclusive rivalry were affected in the same way by changes in vergence angle, although the configuration of the stimulus surface was held constant. These findings confirm the hypothesis that the sieve effect is correlated with the incidence of exclusive rivalry.

Adding and Averaging Effects in Impression Formation as a Function of the Situational Context

Male and female Ss made comparative judgments of paired sets of simultaneously presented income stimuli. The pairs were constructed so that the sum of the values was higher in one set than in the other, while the mean income was simultaneously higher in the latter set than in the former. When the incomes within a set were represented as all belonging to the same person or when the incomes were attributed to different members of a family, both men and women tended to rate higher in economic status whichever sets of stimuli had the higher sums in direct relation to the manipulated discrepancy between sums. When the same stimuli were attributed to different members of a group, both sexes rated higher in economic status whichever sets had the higher arithmetic mean values in direct relation to the manipulated discrepancy between arithmetic means. The significance of this finding is in demonstrating that the stimulus-combination rule in impression formation is at least partially predicated upon situational determinants and that neither simple summation nor simple averaging is an exclusively valid or invalid combinatory principle.

Olfactory analogue to directional hearing

The direction of a sound source can be determined binaurally by using the time difference and the loudness difference of the sound waves arriving at the two ears. Similarly, the direction of an olfactory source can be determined by using the time difference and the difference in sensation magnitude of the olfactory stimuli between the two nostrils as the air surrounding the odorous object is inhaled. Time differences of the order of 0.1 msec can be recognized—a value similar to that found in hearing. Thus the direction of an odor can be determined with a precision of 7–10° in spite of the small distance between the nostrils compared to the distance between the ears. In this respect, there is very little difference between observations made with such odorants as benzol, eucalyptus, cloves, and lavender. The existence of an analogy between hearing and smelling may help to delineate some electrophysiological correlates of the directional sensation, which is so well developed in both senses. localization of olfactory stimuli; interaction between the two nostrils during smelling; time pattern and olfactory localization; olfactory sensation magnitude and duration of stimulus; combination of smell and taste into a single sensation Submitted on November 1, 1963