Three experiments on tachistoscopic perception of visual stimuli demonstrate that the visual system is sensitive to global topological properties. The results indicate that extraction of global topological properties is a basic factor in perceptual organization. (Author)

Rod-isolation techniques show that light-adapted human rods detect flicker frequencies as high as 28 hertz, and that the function relating rod critical flicker frequency to stimulus intensity contains two distinct branches. (MLH)

Training improves the ability of human observers to discriminate between two similar directions of motion. This gradual improvement is specific to the direction on which an observer is trained, enduring for several months. Improvement does not affect motion perception generally, nor does it depend on recognition of details of the movement. (Author)

Contrast thresholds for sine-wave gratings of spatial frequencies of 2, 4, 12, and 16 cycles per degree were determined for normal and disabled readers at a range of stimulus durations. The differences in sensitivity pattern across spatial frequencies was greatest at stimulus durations approximately equal to fixation durations during reading.…

Reports research into the visual fixation of 3- to 11-week old infants as they observed adult faces. Reports a dramatic increase in fixations occurred between 5 and 7 weeks for all conditions. (SL)

Reports effects of context that are entirely perceptual. Visual discrimination was enhanced when line segments were flashed in a region that was perceived as a figure. Discrimination was substantially degraded when the same region was seen as ground although the physical stimulus remained identical throughout figure-ground reversals. (Author/JN)

Research shows that children of about 10 years can remember photographs of faces upside down almost as well as those shown upright and are easily fooled by simple disguises. This ability to encode orientation-specific configurations of a face may reflect maturational changes in the right cerebral hemisphere. (MLH)

Results of discriminating and monitoring tasks indicate that performance deteriorates over time when a specific object must be distinguished from previously presented nonspecific objects in a display which changes quickly. The results offer a basis for distinguishing between perceptual and response processes underlying the vigilance decrement.…

Summarizes the anatomical, physiological, and psychological evidence related to the primate visual system. States that comparison of perceptual abilities with the electrophysiological properties of neurons may help deduce functions of visual areas. (RT)