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Biomedical subjects

B Julesz

Publications and source records attributed to B Julesz.

80 records · Page 5Linked to original sources
PubMed1967

Stereopsis based on vernier acuity cues alone.

Random-line stereograms were generated in which the only monocular cues were minute breaks occurring at random in thin vertical (or horizontal) line grids. The breaks were binocularly correlated. The stereograms yielded global stereopsis (of a square standing out in front of a surface) even with monocular breaks of as little as 16 seconds of arc, which is below the threshold for resolving two lines. This technique led to the clarification of relations between local and global stereopsis.

Humans↗
PubMed1966

Binocular disappearance of monocular symmetry.

In an earlier demonstration binocular shapes were produced from monocularly shapeless, random-dot stereo images. A reversal of this phenomenon is demonstrated. A stereo image is devised in which the monocularly apparent shapes of bilateral symmetry disappear when stereoscopically viewed. This phenomenon sharpens the implications of the earlier one.

Humans↗
PubMedDate not supplied

Parallel versus serial processing in rapid pattern discrimination.

When stimuli are available for just a brief period (approximately 100 ms) only restricted spatial information can be processed by the visual system. If the stimuli are presented very briefly, eye movements are not possible. The time during which the after-image of the stimulus is available for inspection is terminated by presentation of a masking pattern. We show here that in these conditions a small pattern is easily detected against a background made up of many others, only if this target pattern differs from the background patterns in certain local features. In this case the detectability of the target is almost independent of the number of background elements, suggesting that a parallel process is operating. Detection of patterns not differing from their backgrounds in such features requires focal attention which is a serial process. The aperture of this attention is scaled to minimize the number of shifts of attention required.

Discrimination, Psychological↗
PubMedDate not supplied

Enhanced detection in the aperture of focal attention during simple discrimination tasks.

There is increasing evidence that it is possible to shift an aperture of focal attention to a position in visual space independent of fixation and that this can be done much faster than the eyes are able to move. Recently, we showed that such serial scrutiny by the aperture of focal attention is required before an observer is able to tell what a target is (for example, to know whether the orientation of a line segment is horizontal or vertical). Here we considered whether attention directed towards a specific position in the visual field for an orientation discrimination task improves performance on a simple detection task in the area to which attention is directed. We found that a small test flash could be detected when it was positioned near a peripheral line target presented briefly, if the orientation of the target had to be identified. The test flash could not be detected when presented at some distance from the same target or when another target had to be identified. This enhancement implies that even simple identification tasks such as orientation discrimination are not performed passively by the visual system.

Discrimination, Psychological↗