Abstract
Purpose: Results from previous studies indicate that the magnitude of attention effects depends on stimulus features/task (e.g., Lee et al, 1997; Morrone et al, 2002). Here, we used a full/poor attention paradigm to investigate attention effects on two different stimuli/tasks: direction of motion and orientation discrimination. Data were obtained for central (CVF), left (LVF) and right visual field (RVF) to see if attention effects vary across space.
Methods: On the motion task, subjects reported direction of a moving dot field (“left” vs. “right”). On the orientation task, subjects reported the tilt of a 0.8 cpd contrast grating (“clockwise” vs. “counterclockwise”). Stimuli subtended 5 degrees, and RVF and LVF stimuli were centered 5 degrees eccentric to fixation. Thresholds were obtained in two conditions: 1) Full Attention: Subjects performed a single-task, reporting direction (or orientation), and 2) Poor Attention: Subjects performed a dual-task, first counting the number of closed shapes at the fixation point, then reporting stimulus direction (or orientation). Attention effects were calculated as Thrpoor/Thrfull.
Results: For orientation, attention effects were constant across space (LVF=1.29, CVF=1.45, RVF=1.20). However, for motion, attention effects varied across space (LVF=1.74, CVF=1.41, RVF=1.07; p=0.002). The difference between the LVF and RVF was driven by lower thresholds in the LVF under full attention (1.2-fold, p=0.045), yet higher thresholds in the LVF under poor attention (1.3-fold, p=0.006).
Conclusions: The different attention effects for RVF vs. LVF motion suggest that attentional resources for motion may be enhanced in the RVF (perhaps from learning to read left-to-right, see Rayner 1998).
Supported by NSF BCS-0241557 (KRD)