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J M Wolfe

Publications and source records attributed to J M Wolfe.

At least 55 records · Page 3Linked to original sources
PubMed1989

Guided search: an alternative to the feature integration model for visual search.

Subjects searched sets of items for targets defined by conjunctions of color and form, color and orientation, or color and size. Set size was varied and reaction times (RT) were measured. For many unpracticed subjects, the slopes of the resulting RT X Set Size functions are too shallow to be consistent with Treisman's feature integration model, which proposes serial, self-terminating search for conjunctions. Searches for triple conjunctions (Color X Size X Form) are easier than searches for standard conjunctions and can be independent of set size. A guided search model similar to Hoffman's (1979) two-stage model can account for these data. In the model, parallel processes use information about simple features to guide attention in the search for conjunctions. Triple conjunctions are found more efficiently than standard conjunctions because three parallel processes can guide attention more effectively than two.

Adult↗
PubMed1987

The vernier aftereffect.

Exposure to a vernier offset can cause a subsequently viewed straight contour to appear offset in the opposite direction. The size of this vernier aftereffect (VAE) varies systematically with the size of the adapting offset. The VAE may be a version of the tilt aftereffect.

Adaptation, Ocular↗
PubMed1987

Adaptation of the resting states of accommodation.

Without an adequate stimulus to focus, the eyes accommodate for a "resting state" that averages about 1.6 diopter (D) (62 cm). The resting state can be made more "myopic" by adaptation to a near accommodative or vergence stimulus. In the present experiment, 21 subjects were tested for adaptation to both types of stimuli. Resting state was measured before and after adaptation in the dark (dark focus) and in the presence of an illuminated empty field. The authors found that preadaptation resting states were more myopic in the light field than in the dark test conditions; accommodative and vergence stimuli produce myopic shifts in dark and light field resting states; and a subset of the subjects show much larger aftereffects in the light field conditions. These subjects also show the largest difference between preadaptation dark- and light-field measures. Differences between dark- and light-field measures of resting state in these and other experiments may require a re-examination of the hypothesis that there is a single resting state for each subject.

Accommodation, Ocular↗
PubMed1986

Briefly presented stimuli can disrupt constant suppression and binocular rivalry suppression.

An earlier study has shown that the intermittent suppression of one monocular stimulus by another in binocular rivalry does not occur when normally rivalrous stimuli are briefly presented. Constant suppression of stimuli presented to one eye is a common consequence of esotropia during development. A study is reported which demonstrates that constant suppression does not occur when stimuli are briefly presented. The dependence of suppression on stimulus duration is similar in both forms of suppression.

Functional Laterality↗
PubMed1986

Fatigue and structural change: two consequences of visual pattern adaptation.

In a tilt aftereffect (TAE) paradigm, 2 min of adaptation produced an aftereffect that decayed almost completely within 4 min. Four minutes of adaptation produced a TAE that lasted more than 2 wk. Two modes of adaptation contribute to the TAE and account for other aftereffects: short-term fatigue, produced very quickly and long-term structural change, requiring more extended adaptation.

Adaptation, Ocular↗
PubMed1985

Accommodation for flickering stimuli.

A laser optometer was used to measure accommodative responses of three observers for sinusoidal gratings presented in Maxwellian view at optical distances ranging from 0 to 4 diopters. Contrast of the stimuli was modulated spatially at 1.0, 4.2 and 6.5 cycles deg.-1 (cpd), and temporally at six frequencies ranging from 3.0 to 40 Hz. Accommodation was consistently more accurate for the 4.2 cpd than for either the 1.0 or 6.5 cpd gratings. Furthermore, accommodative responsiveness for the 4.2 cpd was not affected by temporal modulation, while that for the other spatial frequencies improved monotonically as a function of temporal frequency. These results reinforce earlier reports that accommodation is most responsive for contrast of intermediate spatial frequencies and they indicate that stimulus flicker generally degrades accommodation for spatial contrast.

Accommodation, Ocular↗
PubMed1984

Short test flashes produce large tilt aftereffects.

Using a staircase method, the tilt aftereffect (TAE) was measured with test flashes of durations ranging from 10 to 600 msec. The TAE is largest with brief duration test stimuli and reaches an asymptotic value at a test flash duration of 200-300 msec. A series of control experiments rule out a variety of explanations for this finding. The decline in TAE magnitude with increasing test duration is not due to decay, nor can the large TAEs produced by brief stimuli be explained in terms of their lower effective luminance or contrast. The results suggest that brief stimuli are processed by a different subset of processes or channels than are longer stimuli.

Adaptation, Ocular↗
PubMed1984

Reversing ocular dominance and suppression in a single flash.

An observer views a long (1-2 sec) monocular stimulus. Following stimulus offset there is a dark interstimulus interval (ISI). After the ISI, brief test flashes are presented to both eyes simultaneously. For ISIs less than 100-200 msec, only the test flash contralateral to the stimulated eye is seen. The test flash in the ipsilateral eye is not seen. For ISIs of 200-1000 msec, the contralateral test flash is seen more clearly and completely than the ipsilateral flash (Experiments 1 and 2). The initial and ipsilateral test flash need not be spatially similar. The initial stimulus can be dim but must be longer than 150 msec (Experiment 3). Experiment 3 precludes forward masking or light adaptation as explanation. The effect is relatively independent of the length of the test flash (Experiment 4). The results can be explained in terms of the known properties of binocular rivalry and reinforce the hypothesis (Fox and Check, 1968) that rivalry acts nonselectively, independent of factors such as spatial frequency, luminance, or orientation.

Adolescent↗
PubMed1984

Global factors in the Hermann grid illusion.

Most explanations of the Hermann grid illusion are local in nature. For example, in Baumgartner's model the effect is generated by the response of cells having concentric on-off or off-on receptive fields. Such models predict that the magnitude of the illusion at a given intersection should be the same whether that intersection is viewed in isolation or in conjunction with other intersections in a grid. Two experiments are reported. The first demonstrates that illusion magnitude grows with the number of intersections. The second shows that this growth is seen when the intersections are arranged in an orderly grid but not when they are placed irregularly. These results suggest that a purely local model for the Hermann grid illusion is not a complete explanation. Global factors must be involved.

Discrimination, Psychological↗
PubMed1983

Shared characteristics of stereopsis and the purely binocular process.

Wolfe and Held (1981) Vision Res. 21, 1755-1759 demonstrated the existence in the human visual system of a purely binocular process. A purely binocular process is defined as a process that responds only to binocular stimulation and not to stimulation of either eye alone. In this paper, some of the characteristics of the purely binocular process are investigated. We find: (1) the process is less sensitive to high spatial frequencies than is the visual system as a whole. (2) It is insensitive to stimuli near the detection threshold for the visual system as a whole. (3) It makes a greater contribution to the appearance of vertically oriented stimuli than to the appearance of horizontally oriented stimuli. (4) The function of the purely binocular process can be disrupted by blurring the image in one eye (artificial anisometropia). Each of these properties of the purely binocular process is similar to the known characteristics of stereopsis. This suggests that the purely binocular process is a necessary stage in stereopsis.

Adaptation, Ocular↗
PubMed1983

Hidden visual processes.

Isoluminant stimulus is an image whose edges are defined only by a change in color, not by change in brightness. The stimulus here is imperfect: the blue parts and the green parts of the image are only as nearly equal in brightness as they can be on the printed page. Moreover, the change in brightness beyond the edge of the page is apparent, and so is the fact that the reader is holding the magazine at reading distance. When such cues are removed under laboratory conditions, subjects faced with an isoluminant stimulus prove unable to bring its edges into focus. This deficiency contributes to making a familiar face hard to recognize. The experiment indicates that the brain process underlying visual accommodation (the focusing of the eyes) cannot "see" color; it is a hidden process distinct from the processes that lead to perception. The image shows Groucho Marx as he appeared in the motion picture Horse Feathers.

Color Perception↗
PubMed1983

Afterimages, binocular rivalry, and the temporal properties of dominance and suppression.

When different contours are presented to the two eyes, an unstable percept, binocular rivalry, is the result. Parts of each set of contours may be seen but the two sets are not seen in the same place at the same time. The contours need not be physically present. Afterimages will produce binocular rivalry. Normal rivalry can be prevented if intermittent stimulation is used. Previous work has shown that orthogonal gratings, flashed for less than 150 ms and separated by more than 150 ms, will appear to fuse into a plaid or checkerboard pattern. In the present experiment this phenomenon is examined with afterimages used to produce rivalry. This abnormal 'fusion' is seen when negative afterimages are stroboscopically illuminated at less than 5 Hz. The results obtained with afterimages are predictable from the previous results obtained with stimuli external to the eye.

Adult↗
PubMed1983

Influence of spatial frequency, luminance, and duration on binocular rivalry and abnormal fusion of briefly presented dichoptic stimuli.

Orthogonal gratings, presented dichoptically, do not fuse into a single percept. Parts of each are seen while other parts are suppressed in an unstable perception (binocular rivalry). However, it has been previously noted that, if the gratings are briefly flashed, they will appear to fuse into a plaid or checkerboard pattern. Three experiments are reported which have been designed to define more clearly the spatial and temporal parameters of this effect in the hope that this would lead to better understanding of the normal mechanisms of dominance and suppression. Stimuli appear fused if flashed for less than 150 ms. The effect is independent of substantial changes in spatial frequency and luminance. Single flashes that appear fused when presented in isolation produce rivalry if separated by intervals less than about 150 ms. Intervals greater than 150 ms produce continued abnormal fusion. Possible mechanisms are discussed.

Adolescent↗
PubMed1982

Binocular adaptation that cannot be measured monocularly.

The tilt aftereffect (TAE) is used to demonstrate the existence of a purely binocular process in human vision. A purely binocular process is a process that can be activated only by matched inputs to the two eyes. It is insensitive to monocular stimulation. The TAE can be produced by exposure to a bipartite field with the top tilted to the left of vertical, the bottom to the right. After such adaptation a pair of colinear lines appears bent in the opposite direction. A cyclopean random-dot stereogram can be used as an adapting stimulus. It produces a 2 degree TAE when a cyclopean test stimulus is used and a 1 degree TAE when a binocular but noncyclopean test stimulus is used. If the same noncyclopean pattern is viewed monocularly, no TAE is measurable. The TAE does not transfer from cyclopean adaptation to monocular testing. Apparently, cyclopean stimuli activate a 'purely binocular process' that cannot be activated by either eye alone.

Adaptation, Ocular↗