Abstract
Introduction: Previous research has revealed performance advantages for stimuli presented across (bilateral) rather than within (unilateral) the left and right hemifields on a variety of spatial attention tasks (e.g., Awh & Pashler, 2000; Chakravarthi & Cavanagh, 2009; Reardon, Kelly, & Matthews, 2009). Here we investigated whether a bilateral advantage would also be observed for tasks limited by the temporal resolution of attention. Method: Twenty-three Denison University undergraduates completed a 3×3 within-subject experiment. The independent variables were attentional condition (bilateral, unilateral, diagonal) and distracter condition (absent, static, dynamic). Stimuli were Gabor patches in the 4 corners of the screen (14.55 deg diagonally from fixation); 2 were pre-cued as targets on each trial. In two-thirds of trials, 2 Gabor distracters were presented between each pair of corner target positions. In half of these trials, the distracters did not change orientation throughout the duration of stimulus presentation. In the remaining distracter trials, distracter orientations changed orthogonally at random time intervals. After correctly identifying a foveally flashed letter, participants judged whether or not the cued targets had changed orientation simultaneously. Results: When distracters were absent, proficiency (d′/RT) was significantly lower in the diagonal condition than in either of the bilateral or unilateral conditions, which were statistically indistinguishable. This diagonal disadvantage was eliminated in the presence of either distracter type. Discussion: The significantly lower proficiency in the diagonal condition-in which targets were in opposite hemifields-argues against an effect of laterality on this task. This lack of laterality effects in the temporal resolution of attention contrasts with the significant laterality effects previously reported on spatial attention tasks (Awh & Pashler; Chakravarthi & Cavanagh; Reardon, Kelly, & Matthews). This suggests different constraints on the spatial versus temporal resolution of attention, which is consistent with the conclusion of Aghdaee and Cavanagh (2007).