Siobhan McCourt¹, Matt Peterson, Miguel Eckstein², Brad Duchaine¹; ¹Dartmouth, ²University of California, Santa Barbara

Individuals’ first eye movements to faces are consistently directed to a preferred fixation location (PFL). Observers show substantial individual differences in the vertical position of their PFL. Each individual also has an optimal fixation location (OFL) on the face at which performance is best and then rapidly declines when fixations deviate from it (retinotopic tuning). Most people’s PFLs and OFLs are tightly linked (Peterson & Eckstein, 2013), and these locations might be expected to remain stable across a lifetime, with participants consistently preferring to fixate on their optimal position. Two findings, however, suggest these positions may migrate down the face. PFLs were higher in younger adults than older adults in a small sample (Peterson et al., 2019), and discrimination of the eyes declines as adults age, whereas discrimination of the mouth remains stable (Fry et al., 2023). Here, we investigate PFLs’ shift down the face with age, and the relationship between PFLs and retinotopic face tuning. We utilized iTrak, a novel method for determining single fixation locations in internet-based studies. iTrak briefly presents a target stimulus that is immediately followed by a 27x27 grid of bigrams for 200ms. Participants must respond to the target stimulus and report the bigram they saw, with the bigram indicating fixation location. Participants completed two sex discrimination tasks: a free-fixation task to determine PFLs and a forced-fixation task to estimate retinotopic tuning curves. Results from the free-fixation task (N=43, age range=18-64) showed no correlation between age and vertical PFL r=-.05, p=.73). The forced-fixation task (N=19) revealed the expected negative correlation between distance from PFL and sex discrimination performance (r=-.52, p=.02). These findings indicate that PFLs remain stable with age and the match between PFLs and OFLs demonstrates that iTrak effectively collects eye position data.