Reading Aloud: On the Determinants of the Joint Effects of Stimulus Quality and Word Frequency

There are multiple reports, in the context of the time taken to read aloud, that the joint effects of stimulus quality and word frequency (a) interact when only words appear in the list but (b) are additive when nonwords are intermixed with words (O'Malley & Besner, 2008). This triple interaction has been explained in terms of the idea that different processing modes are in play in these different contexts. Processing is cascaded when only words appear in the list, allowing the effect of stimulus quality to influence the downstream process(es) affected by word frequency. In contrast, when nonwords appear in the list an early process affected by stimulus quality, but not word frequency, is staged (thresholded) so as to reduce the probability of lexicalizations (reading a nonword as a word) when stimulus quality is low. The present experiment addresses the issue of whether such thresholding in the presence of nonwords is driven by the orthography or phonology of the nonwords included in the stimulus set. Participants read words aloud that varied in word frequency and were randomly intermixed with nonwords that all sounded identical to words (e.g., BRANE for BRAIN). Stimulus quality and word frequency had additive effects on the time to read aloud in this context, consistent with the view that it is the orthography of the nonwords that matters. Other aspects of the results suggest that between level feed-back is in play when this particular kind of nonword is used.