Abstract
Experiment 1 was a study in which three times during the school year (in September, February, and April) first graders performed a discrete-trial Stroop task in which they named the colors of stimuli that were either letters, high-frequency words, or low-frequency words. The amount of interference caused by these stimuli was assessed by comparing the naming times to a control condition where the subject named a series of X's. In each testing period the interference caused by letters exceeded that caused by high-frequency words. There was also a nonsignificant tendency for interference caused by high-frequency words to exceed that caused by low-frequency words. There was a marked increase in interference between September and February, but very little change between February and April, indicating that the automaticity function had already flattened out by the end of first grade. There was a tendency for better readers to display more interference and to show interference earlier in the year. Experiment 2 replicated the developmental trends displayed in Experiment 1 and explored the relationship between interference and the speed and accuracy with which subjects named the stimuli. The overall pattern of results in the two experiments was reasonably consistent with the automaticity model of reading developed by LaBerge and Samuels (1974).