Texture segmentation along the horizontal meridian: Nonmonotonic changes in performance with eccentricity.

Abstract

In 3 experiments, subjects were required to detect the presence of a small region of disparate texture embedded in a larger background at a range of eccentricities. Detection performance always peaked several degrees from fixation. Experiment 1 showed that the location of the peak was not retinally specific; scaling the display changed the location of the performance peak. Experiment 2 showed that poor foveal performance could not be explained by cross-frequency interference; filtering out high spatial frequencies did not lead to improved foveal performance. Experiment 3 showed that the effect is not unique to textures comprising left and right oblique line segments. A parsimonious account of these data is that, at the fovea, there is a mismatch between the scale of the texture and the scale of the mechanisms responsible for encoding texture differences. This mismatch diminishes as the textures are moved further into the periphery.

The effects of transient attention on spatial resolution and the size of the attentional cue

“…To further probe this resolution hypothesis, we enlarged the scale of the texture. Consistent with previous findings (Gurnsey et al, 1996;Joffe & Scialfa, 1995), increasing the texture scale moved the performance peak to farther eccentricities. Moreover, the central attentional impairment changed as a function of texture scale: Performance was impaired in a larger range of central retinal locations as the scale of the texture increased.…”

“…Instead, performance peaks at midperipheral locations and drops when the target appears at more central or farther peripheral locations. The finding that performance in this texture segregation task drops at central locations-the central performance drop-is attributed to a mismatch between the average size of spatial filters at the fovea and the scale of the texture (see, e.g., Gurnsey, Pearson, & Day, 1996;Kehrer, 1997). There is ample evidence that we process visual stimuli by means of parallel spatial filters.…”

“…At more peripheral regions, the filters' average size increases gradually, presumably reaching optimal size around the area of peak performance. At farther locations, the filters are too big, and their low resolution limits performance (e.g., Gurnsey et al, 1996;Joffe & Scialfa, 1995;Kehrer, 1989Kehrer, , 1997Potechin & Gurnsey, 2003).…”

A central performance drop with luminance stimuli requiring spatial integration

“…The performance drop in the foveal area may have been due to a shift in response criterion by the participants (in the direction of more conservative response behavior), and not to a shift in sensitivity. Although Gurnsey et al (1996), for example, showed that this was not the case in their conditions, it is still necessary to ensure that this also holds for luminance stimuli. Therefore, in Experiment 2 we collected data on the false alarm rate per target position in order to be able to calculate d .…”

“…In other words, performance first increases with increasing eccentricity and-after reaching a peak-declines with further eccentricity. This pattern of results is known as the central performance drop (CPD; Kehrer, 1987Kehrer, , 1989; see also, e.g., Gurnsey, Pearson, & Day, 1996;Joffe & Scialfa, 1995;Morikawa, 2000; and is mainly observed in texture segmentation tasks that use orientation differences between target and context elements.…”