Syllable onsets are perceptual reading units.

Syllable onsets are defined as the initial consonant or consonant cluster in a syllable (e.g., BR in BREAD). In the present study, using a letter detection paradigm and French words, we tested whether syllable onsets are processed as units by the reading system. In Experiment 1, we replicated Gross, Treiman, and Inman's (2000) result of observing no difference between the detection latencies of letters embedded in a multi-letter syllable onset (e.g., c in ECLATER) relative to a single-letter syllable onset (e.g., C in ECARTER). In Experiment 2, participants took longer to detect the target letter when it was in the second position of a multi-letter onset (e.g., L in TABLIER) than when it was a single-letter onset (e.g., L in ECOLIER). In Experiment 3, this position effect was replicated for graphemes. In Experiment 4, we tested and ruled out an alternative explanation of the unitization effect, in terms of lateral masking. These results indicate that syllable onsets are processed as perceptual units by the reading system and that the unitization effect is position dependent.