Abstract
A previous study (Enns and Di Lollo, 2000) reported that the amount of object substitution masking (OSM) is influenced by the number of distractors in an orientation discrimination task. The current study investigates how the amount of OSM is influenced by the sizes of stimulus and attention field. Stimuli were Landolt Cs, and their size was either 1.2° (small) or 2.4° (large). Each display had four Landolt Cs, and each Landolt C was presented either at 1.4° (close) or 2.8° (far) away from the fixation cross. Note that we did not present large stimuli in the close distance. We also varied the duration of a trailing mask in five levels (12ms, 52ms, 104ms, until response, and no mask). Four Landolt Cs were presented simultaneously for 12ms, and one of them was presented with four dots. After 52ms, only four dots reappeared for the pre-specified duration. Participants were asked to report the orientation of the Landolt C presented with four dots. We found that the orientation discrimination did not differ between the small-close and large-far conditions but significantly differed between the small-close and small-far conditions. The amount of OSM was the largest in the small-far condition, even when a trailing mask was presented only for 12ms. These results suggest that the amount of OSM is related to the sizes of stimulus and attention field, consistent with the prediction from the normalization model of attention (Reynolds and Heeger, 2009).
Meeting abstract presented at VSS 2013