Effects of aging, word frequency and text stimulus quality on reading across the adult lifespan: Evidence from eye movements

Reductions in stimulus quality may disrupt the reading performance of older adults more compared to young adults due to sensory declines that begin early in middle age. However, few studies have investigated adult age differences in the effects of stimulus quality on reading, and none have examined how this affects lexical processing and eye movement control. Accordingly, we report two experiments that examine the effects of reduced stimulus quality on the eye movements of young (18-24 years), middle-aged (41-51 years) and older (65+ years) adult readers. In Experiment 1, participants read sentences which contained a high or low frequency critical word and that were presented normally or with contrast reduced so that words appeared faint. Experiment 2 further investigated the effects of reduced stimulus quality using a gaze-contingent technique to present upcoming text normally or with contrast reduced. Typical patterns of age-related reading difficulty (e.g., slower reading, more regressions) were observed in both experiments. In addition, eye movements were disrupted more for older than younger adults when all text (Experiment 1) or just upcoming text (Experiment 2) appeared faint. Moreover, there was an interaction between stimulus quality and word frequency (Experiment 1), such that readers fixated faint lower frequency words for disproportionately longer. Crucially, this effect was similar across all age groups. Thus, while older readers suffer more from reduced stimulus quality, this additional difficulty primarily affects their visual processing of text. These findings have important implications for understanding the role of stimulus quality on reading behavior across the lifespan.