Consonant/vowel asymmetries in letter position coding during normal reading: evidence from parafoveal previews in Thai

Studies have revealed that consonants and vowels serve different roles during linguistic processing. Masked transposed-letter priming effects (i.e., faster word-identification times for words preceded by a transposed-letter than substitution-letter prime) occur for consonants but not for vowels in lexical decision (Perea & Lupker, 2004). Potential differences in letter position coding for consonants and vowels during silent normal reading were investigated in Thai using the boundary paradigm (Rayner, 1975). Thai has a distinctive alphabetic script with vowels taking a relatively subsidiary role in relation to consonants. Parafoveal processing of nonadjacent transposed-letter effects involving consonants and vowels was examined. Results for gaze durations revealed a transposition effect involving consonants but not vowels—thus extending previous findings with the masked priming technique but in a more ecological setting. Similar differential effects for consonants and vowels for first and single fixations were not found. An explanation is that consonants and vowels are not differentiated at this initial low level stage of processing (Johnson, 2007; Perea & Acha, 2009); it is only later in processing (as measured by gaze durations) that consonant/vowel status comes into play. Results support the claim that there are some fundamental processing asymmetries between vowels and consonants in normal reading.