Abstract
Multifocal attentional tracking is characterized by hemifield independence (Alvarez & Cavanagh, JOV, 2015). Whereas the maximum tracking speed declines with the addition of new targets in the same hemifield, it is virtually unaffected by new targets in the opposite hemifield (Holcombe & Chen, Cognition, 2012). Hemifield independence likely relies on a network of competitive inter-hemispheric interactions (Battelli et al., JOCN, 2009). Considering known age-related changes in hemispheric asymmetry and cross-hemispheric communication (Davis et al., Cereb. Cortex, 2012), hemifield independence in attentional tracking may be affected in ageing and may contribute to the observed declines in multiple object tracking in ageing (Sekuler et al., Perception, 2008). We examined the effect of target and distracter laterality on tracking in 11 younger (M = 24.5 y.) and 11 older (M = 68.2 y.) participants. Stimuli comprised pairs of circles centred in one of four quadrants. There were 5 conditions: 2 unilateral targets (left or right), 2 bilateral targets (upper or lower), with and without distracter pairs in the remaining quadrants, and 4 targets (one in each quadrant). On each trial, participants tracked the targets while the circle pairs rotated at a constant speed along circular trajectories (2.5° radius) for 5s. Rotation speed varied across trials according to the method of constant stimuli. As expected, younger participants showed slower thresholds in the unilateral (M = 1.74, SD = 0.39) compared to the bilateral (M = 1.84, SD = 0.35) conditions. This bilaterality advantage was also seen in the older group (bilateral: M= 1.09, SD = 0.76; unilateral: M=0.93, SD = 0.65). There was no significant age by laterality interaction. Distracter pairs had no effect on performance in either group. Finally, thresholds for tracking four targets were the same as thresholds for tracking two unilateral targets in both groups. These results point to preserved hemifield independence in attentional tracking in ageing.
Meeting abstract presented at VSS 2016