Differential roles of distracters in reflexive and memory-based localization

Abstract

We investigated the effects of spatial and temporal factors on manual localization of a visual target by measuring accuracy, precision, and bias. Spatial factors included manipulation of display as with or without distracters, with invariant or variant distracters, and with near or far distracters, respectively, in Experiments 1, 2, and 3. The target and distracters were of 1degrees dots differing only by luminance parameter; they were presented concurrently for 150 or 1000 ms while observers had to memorize the target location maintaining a fixed gaze. The observers' task was to reproduce the location of the target with a mouse cursor available 150 ms following stimuli offset. Results from all experiments showed that localization performance for a briefly exposed target was as accurate and precise as that for a long exposed target. Moreover, manipulation of spatial factors had no systematic effects on accuracy and precision except that near distracters yielded higher precision. Interestingly, localization performance was unbiased in 150 ms condition when there were distracters in the display, while being biased towards the fovea in 1000 ms condition regardless of their presence or absence. These results suggest a temporal dynamics in dominance-suppression between egocentric and exocentric cues in the construction of memory for location.

Exploring the edges of visual space: The influence of visual boundaries on peripheral localization

“…One limitation of the two-process model is that it fails to predict whether a foveal or peripheral bias should occur in a given task, as the model focuses on absolute accuracy rather than bias. One proposal to account for biases is that the dissociation between the point of fixation and the locus of covert attention determines the direction of biases in spatial localization tasks, at least using perceptual reports (Uddin, 2006; Uddin et al, 2005a; Uddin, Kawabe, & Nakamizo, 2005b). According to this model, when fixation is maintained centrally and a peripheral target is presented, attention is focused at the point of fixation, resulting in a foveal bias in perceived location.…”

Gaze direction and the extraction of egocentric distance

“…A bias of this kind would predict overestimation when the point of regard is below the target and underestimation when the point of regard is above the target. However, there are also investigators that have reported a foveal bias (e.g., Adam et al, 2008; Tsal & Bareket, 2005; Uddin, Kawabe, & Nakamizo, 2005). Biases of these kinds would predict underestimation when the point of regard is below the target and overestimation when the point of regard is above the target.…”