Age changes in the missing-letter effect reflect the reader's growing ability to extract the structure from text.

Readers searching for a target letter in text are more likely to miss it in frequent function words than in less frequent content words, and the magnitude of this effect increases with age. While this increase has been taken to indicate that proficient readers process familiar words in terms of larger orthographic units, we propose that it reflects the reader's growing ability to extract the structure of text, resulting in a reduced emphasis on function than on content words. Indeed, comparing 2nd graders (7 to 7 1/2 years) and college students (Experiment 1) this increase was found even when function and content words were equated for frequency. Scrambling words within a sentence (Experiment 2) improved letter detection in function compared to content words among 7th graders (12 to 13 years) and college students, but not among 3rd graders (8 to 9 years). Although letter detection was also affected by word frequency, the age differences noted above are possibly due not to the increasing familiarity of words, but rather to the growing sensitivity to their structural role in text.