Adult age differences in the effects of word frequency during visual letter identification

Abstract

The experiment reported in this investigation examined whether older adults process both letter-level and word-level information simultaneously during a letter identification task as younger adults apparently do (Allen & Madden, in press; Johnson, Allen, & Strand, in press). Thus, the present study was an attempt to determine if older adults use parallel processing under the same conditions as do young adults. There was a curvilinear relationship between initial-letter identification reaction time (RT) and word frequency for younger adults. That is, letter identification RT for medium-high frequency words was greater than for very-high, medium-low, and low-low frequency words. However, the older adults exhibited longer letter identification RT for low-low frequency words than for very-high and medium-high frequency words. These data are consistent with a model that suggests younger adults process dual representations (i.e., letter-level and word-level) of words, whereas older adults form a unitary, word-level representation of words and then use top-down processing in order to determine the initial letter of words.