Case mixing impedes early lexical access: converging evidence from the masked priming paradigm

When letters are presented in mixed case (e.g., "PlAnE), word recognition is slowed. This case-mixing effect has been used to argue that early stages of word recognition operate holistically (on the entire visual word form) rather than merely letter-by-letter. Contrary to this holistic view, however, a masked priming study (Perea, Vergara-Martinez, & Gomez, Cognition 142:39-43, 2015) with Spanish words argued that case mixing has no effect on early stages of visual word recognition. Their participants made lexical decisions on an uppercase target (e.g., "PLANE") preceded by an identical prime (e.g., "plane") or an unrelated prime (e.g., "music"), presented in lowercase or mixed case. Because priming effects (unrelated-identical) were unaffected by case mixing, they concluded that case mixing does not impede early lexical access. We examined whether this finding applies to English words, while also including lowercase targets to prevent a strong bias against holistic word recognition. We found larger priming effects from lowercase primes than mixed-case primes regardless of target case (lowercase vs. uppercase) and whether target case was varied within blocks (Experiment 1) or between blocks (Experiment 2). Contrary to Perea et al.'s findings for Spanish, our results suggest an early locus for the case-mixing effect, consistent with the holistic view of word recognition.