Letter chunk frequency does not explain morphological masked priming: Affix frequency in masked priming

Research on visual word identification has extensively investigated the role of morphemes, recurrent letter chunks that convey a fairly regular meaning (e.g., lead-er-ship). Masked priming studies highlighted morpheme identification in complex (e.g., sing-er) and pseudo-complex (corn-er) words, as well as in nonwords (e.g., basket-y). The present study investigated whether such sensitivity to morphemes could be rooted in the visual system sensitivity to statistics of letter (co)occurrence. To this aim, we assessed masked priming as induced by nonword primes obtained by combining a stem (e.g., bulb) with (i) naturally frequent, derivational suffixes (e.g., -ment), (ii) non-morphological, equally frequent word-endings (e.g., -idge), and (iii) non-morphological, infrequent word-endings (e.g., -kle). In two additional tasks, we collected interpretability and word-likeness measures for morphologically-structured nonwords, to assess whether priming is modulated by such factors. Results indicate that masked priming is not affected by either the frequency or the morphological status of word-endings, a pattern that was replicated in a second experiment including also lexical primes. Our findings are in line with models of early visual processing based on automatic stem/word extraction, and rule out letter chunk frequency as a main player in the early stages of visual word identification. Nonword interpretability and word-likeness do not affect this pattern.