Adult age differences in early word processing: Evidence from eye movements during sentence reading

This thesis reports seven experiments which examine whether young and older adult readers differ in aspects of early word processing during reading. Further, this thesis explores whether the mechanisms underlying these processes differ between young and older adult readers. Despite age-related reading difficulties being well documented, little is known about the mechanisms underlying these difficulties. Many aspects of older adults’ processing have not previously been examined in detail. Accordingly, the current experiments provide a novel examination of various aspects of older adults’ early word recognition processing. Findings from Experiment 1 indicate that young and older adults make similar use of parafoveal orthographic information and have a perceptual span which is similar in size and symmetry. Experiments 2 and 3 revealed that older adults experience greater difficulty when reading low-contrast text than young adults. Further, Experiment 2 provided an initial indication that middle-aged readers do not yet experience the reading difficulty typically associated with older age. Experiments 4 and 5 suggest that young and older adults process letter position similarly (e.g. similar coding of “problem” and “rpoblem”). Experiments 4 and 5 also highlighted the potential for effects to be inflated in measures sensitive to rereading for groups that are more likely to reread. These groups may experience a “double-whammy” due to a greater likelihood of words being processed multiple times. Finally, Experiments 6 and 7 indicate that older adults may make more word misperception errors during reading when two words are both visually and orthographically similar and when the alternative reading of the word is higher frequency (e.g. mistaking “spice” for “space”). Overall, these experiments have advanced our understanding of adult age differences in early word recognition processes. These findings highlight key areas for development for future studies, models of eye movement control during reading and models of visual word recognition.