The role of phonetic processes in letter detection: A reevaluation

Abstract In seven experiments we investigated the finding that subjects often fail to detect the letter f in the word of . This effect was depressed in Experiment 1 when asterisks were inserted between all letters in a passage, suggesting that unitization processes contributed to the effect. Experiment 2 compared detection of the letters o and f and found a significant but much smaller effect for o , indicating that unitization can only provide a partial explanation for the effect with f . In Experiment 3 the effect was maintained for the letter f but not the letter o when subjects searched an auditory version of the passage, which implies that phonetic processes are involved in the effect for f . Experiments 4, 5, and 6 demonstrated that the effect is still observed when subjects are told to search for v as well as f , even with an auditory presentation of the passage and even when instructed to detect the phonemes rather than the letters. These findings are inconsistent with the proposal by Read (1983 , Memory and Cognition , 11, 390–399) that subjects miss the f in of because they are searching only for the phoneme /f/. Experiment 7 showed that the effect can be reduced if subjects are led to interpret the letter sequence of as a misspelled version of the word off and can be eliminated entirely if subjects are also required to write down every letter of the passage. The findings of Experiment 7 provide further evidence that unitization and phonetic processes together contribute to the effect. The results as a whole are taken to imply that both letter and phoneme levels need to be included in models of word identification as well as a cross-checking or communication between the two levels.