Eye movements and the perceptual span in real-world scene search and sentence reading in young and older adults

The study was designed to measure the size of the visual or perceptual span in young and older adults in two everyday visual-cognitive tasks. Each participant completed an object-in-scene search task and a sentence reading task. Span size was estimated using the gaze-contingent moving window paradigm, with a low-pass filtered background. For each task, we tested nine window radii measuring 2 – 10º (visual search) and 2 – 18 characters (reading; 3.5 char = 1º). Search times and reading times in the no-window control condition were longer for older than for young adults. Relative to this baseline, in the object search task there was no difference in visual span size for the two age groups. The perceptual span during reading was somewhat smaller for older than for young adults, in agreement with previous research. The span was much larger during object-in-scene search (8º) than sentence reading (10 and 8 characters for young and older participants, respectively). Although this task effect has been suggested in the literature, it has never been tested directly in a within-subject design. Saccade amplitudes and fixation durations showed specific task and age-group effects, which contributed to the observed pattern of results.