The time course of the lowercase advantage in visual word recognition: An ERP investigation

Previous word identification and sentence reading experiments have consistently shown faster reading for lowercase than for uppercase words (e.g., table faster than TABLE). A theoretically relevant question for neural models of word recognition is whether the effect of letter-case only affects the early prelexical stages of visual word recognition or whether it also influences lexical-semantic processing. To examine the locus and nature of the lowercase advantage in visual word recognition, we conducted an event-related potential (ERP) lexical decision experiment. ERPs were recorded to words and pseudowords presented in lowercase or uppercase. Words also varied in lexical frequency, thus allowing us to assess the time-course of perceptual (letter-case) and lexical-semantic (word-frequency) processing. Together with a lowercase advantage in word recognition times, results showed that letter-case influenced early perceptual components (N/P150), whereas word frequency influenced lexical-semantic components (N400). These findings are consistent with those models of written word recognition that assume that letter-case information from the visual input is quickly mapped onto the case-invariant letter and word units that drive lexical access.