Biomedical subjects

F H Durgin

Publications and source records attributed to F H Durgin.

10 recordsLinked to original sources

PubMed2001

Visual aftereffects of sequential perception: dynamic adaptation to changes in texture density and contrast.

Two new aftereffects are described in which the comparison of successively presented textures can be affected by prior exposure (adaptation) to biased sequences. A dynamic aftereffect of texture density can be produced using changes in non-Fourier texture density (using balanced-dot textures). An analogous dynamic aftereffect is demonstrated for texture contrast. These two effects are dissociated experimentally by the near absence of cross-adaptation. Evidence is also presented that the density effect is not one of texture motion (e.g. expansion/contraction of texture).

Adaptation, Physiological↗

PubMed2001

Texture contrast aftereffects are monocular; texture density aftereffects are binocular.

Two experiments examined interocular transfer for simple and dynamic aftereffects of density and contrast. Simple aftereffects of texture contrast were shown to be primarily monocular. Texture density aftereffects were shown to be primarily binocular. Similarly, dynamic aftereffects to repeated changes in contrast were found to be completely monocular; those to repeated changes in density were found to be entirely binocular. Since contrast and density aftereffects differ in their sensitivity to eye-of-origin, they likely depend on different neural loci, and are not manifestations of the same underlying adaptation. Consistent with this conclusion, it is proposed that, whereas contrast normalization (and perhaps contrast aftereffects) may be localized to simple cells in V1, density coding and normalization require computations only available in complex cells and beyond.

Adaptation, Physiological↗

PubMed2000

The reverse Stroop effect.

In classic Stroop interference, manual or oral identification of sensory colors presented as incongruent color words is delayed relative to simple color naming. In the experiment reported here, this effect was shown to all but disappear when the response was simply to point to a matching patch of color. Conversely, strong reverse Stroop interference occurred with the pointing task. That is, when the sensory color of a color word was incongruent with that word, responses to color words were delayed by an average of 69 msec relative to a word presented in gray. Thus, incongruently colored words interfere strongly with pointing to a color patch named by the words, but little interference from incongruent color words is found when the goal is to match the color of the word. These results suggest that Stroop effects arise from response compatibility of irrelevant information rather than automatic processing or habit strength.

Color Perception↗

PubMed1999

Visuomotor adaptation without vision?

In 1995, an aftereffect following treadmill running was described, in which people would inadvertently advance when attempting to run in place on solid ground with their eyes closed. Although originally induced from treadmill running, the running-in-place after-effect is argued here to result from the absence of sensory information specifying advancement during running. In a series of experiments in which visual information was systematically manipulated, aftereffect strength (AE), measured as the proportional increase (post-test/pre-test) in forward drift while attempting to run in place with eyes closed, was found to be inversely related to the amount of geometrically correct optical flow provided during induction. In particular, experiment 1 (n=20) demonstrated that the same aftereffect was not limited to treadmill running, but could also be strongly generated by running behind a golf-cart when the eyes were closed (AE=1.93), but not when the eyes were open (AE=1.16). Conversely, experiment 2 (n=39) showed that simulating an expanding flow field, albeit crudely, during treadmill running was insufficient to eliminate the aftereffect. Reducing ambient auditory information by means of earplugs increased the total distances inadvertently advanced while attempting to run in one place by a factor of two, both before and after adaptation, but did not influence the ratio of change produced by adaptation. It is concluded that the running-in-place aftereffect may result from a recalibration of visuomotor control systems that takes place even in the absence of visual input.

Adaptation, Psychological↗

PubMed1997

Texture density aftereffects in the perception of artificial and natural textures.

Three experiments are reported concerning the texture density aftereffect. The experiments address the question of how visual texture density information is encoded by examining patterns of transfer between different textures. In the first two experiments, it is shown that manipulation of spatial frequency and orientation information does not affect the direction of the aftereffect of density (reduction in perceived density), though similarity between adaptation and test textures does influence aftereffect strength. The third experiment demonstrates that adaptation to density differences in artificial textures in which spatial frequency information is held constant produces density aftereffects in naturalistic test textures in which density and spatial frequency covary.

Adaptation, Ocular↗

PubMed1997

Global precedence in visual search? Not so fast: evidence instead for an oblique effect.

The evidence from an earlier report of global precedence in visual search is reexamined. Two new experiments are reported. The results of the first experiment indicate that the confusability of oblique orientations (a class-2 oblique effect) rather than global precedence was responsible for the earlier results. The results of the second experiment show that the effect critically depends on the presence of heterogeneous distractors rather than on differences in raw processing speed for different spatial scales. The possible role of symmetry is discussed.

Humans↗

PubMed1996

Visual learning in the perception of texture: simple and contingent aftereffects of texture density.

Novel results elucidating the magnitude, binocularity and retinotopicity of aftereffects of visual texture density adaptation are reported as is a new contingent aftereffect of texture density which suggests that the perception of visual texture density is quite malleable. Texture aftereffects contingent upon orientation, color and temporal sequence are discussed. A fourth effect is demonstrated in which auditory contingencies are shown to produce a different kind of visual distortion. The merits and limitations of error-correction and classical conditioning theories of contingent adaptation are reviewed. It is argued that a third kind of theory which emphasizes coding efficiency and informational considerations merits close attention. It is proposed that malleability in the registration of texture information can be understood as part of the functional adaptability of perception.

Adaptation, Physiological↗

PubMed1996

Visual aftereffect of texture density contigent on color of frame.

An aftereffect of perceived texture density contingent on the color of a surrounding region is reported. In a series of experiments, participants were adapted, with fixation, to stimuli in which the relative density of two achromatic texture regions was perfectly correlated with the color presented in a surrounding region. Following adaptation, the perceived relative density of the two regions was contingent on the color of the surrounding region or of the texture elements themselves. For example, if high density on the left was correlated with a blue surround during adaptation (and high density on the right with a yellow surround), then in order for the left and right textures to appear equal in the assessment phase, denser texture was required on the left in the presence of a blue surround (and denser texture on the right in the context of a yellow surround). Contingent aftereffects were found (1) with black-and-white scatter-dot textures, (2) with luminance-balanced textures, and (3) when the texture elements, rather than the surrounds, were colored during assessment. Effect size was decreased when the elements themselves were colored, but also when spatial subportions of the surround were used for the presentation of color. The effect may be mediated by retinal color spreading (Pöppel, 1986) and appears consistent with a local associative account of contingent aftereffects, such as Barlow's (1990) model of modifiable inhibition.

Adult↗

PubMed1995

Comparing depth from motion with depth from binocular disparity.

The accuracy of depth judgments that are based on binocular disparity or structure from motion (motion parallax and object rotation) was studied in 3 experiments. In Experiment 1, depth judgments were recorded for computer simulations of cones specified by binocular disparity, motion parallax, or stereokinesis. In Experiment 2, judgments were recorded for real cones in a structured environment, with depth information from binocular disparity, motion parallax, or object rotation about the y-axis. In both of these experiments, judgments from binocular disparity information were quite accurate, but judgments on the basis of geometrically equivalent or more robust motion information reflected poor recovery of quantitative depth information. A 3rd experiment demonstrated stereoscopic depth constancy for distances of 1 to 3 m using real objects in a well-illuminated, structured viewing environment in which monocular depth cues (e.g., shading) were minimized.

Adult↗

PubMed1995

On the filling in of the visual blind spot: some rules of thumb.

In monocular viewing there is a region in the peripheral visual field that is blind owing to the absence of photoreceptors at the site where the optic nerve exits the eye. This region, like certain other blind spots, nonetheless appears filled in. Several novel demonstrations of filling in at the blind spot have recently been reported. Here the implications of many of these effects are critically reevaluated. Specifically, it is argued that many blind-spot phenomena taken to support early filling in (eg pop out and alteration in apparent motion) are actually consistent with the thesis that the visual blind spot is treated by early perceptual processing as a region of reduced or absent information. In support of this, it is shown that many perceptual effects observed in blindspot completion are similar in detail to the amodally perceived completion of partly occluded objects viewed somewhat peripherally. The goals were to point out striking similarities between blind-spot completion and the amodal completion of occluded parts of surfaces, and to provide a common theoretical framework for understanding these phenomena in the context of surface segregation and perceptual interpolation.

Humans↗