Lexical Processing A Word Recognition

In visual word recognition, a whole word may be viewed at once (provided that it is short enough), and recognition is achieved when the characteristics of the stimulus match the orthography (i.e., spelling) of an entry in the mental lexicon. Speech perception, in contrast, is a process that unfolds over time as the listener perceives subsequent portions of the word. Upon hearing the first syllable of a spoken word such as the "un" in "understand," several words may be consistent with the input (e.g., "under," "until," and "untie"). As subsequent portions are perceived the pool (or "cohort") of words will be narrowed down, until only one word remains.

Despite these differences in the temporal course of processing, there are many commonalities in spoken and written word recognition. In both cases, the goal is to go from the perceptual information to the lexical form in order to access semantic and syntactic information about the word. In visual word recognition, a letter level intervenes between visual processing and lexical access. In auditory word perception, it is often assumed that a phoneme level intervenes between the acoustic input and lexical access. Phonemes are assumed to be the basic sound units of speech perception (and production). In English there are approximately 40 different phonemes, corresponding to the consonant and vowel sounds. The phonemes of other languages overlap those of English to a large degree, although some languages may lack some of the phonemes in English or may contain phonemes that do not exist in English. For example, Chinese does not distinguish between the "l" and "r" phonemes, and some African languages include clicking sounds as phonemes.

There is general agreement that spoken and written word recognition involve access to the same semantic and syntactic representations. There has been some disagreement, though, about whether there are separate lexical representations for spoken and written words. Some researchers have argued that written words have to be transformed into a sound representation in order to access semantic and syntactic information about the word. If so, then only a phonological representation (e.g., one that indicates the sequence of constituent phonemes and the stress pattern) is needed for each word. However, considerable neuropsychological evidence suggests that there are separate phonological and orthographic represen tations for words, and that access to word meaning can proceed for written words without conversion to a phonological form. Nonetheless, it is the case that for normal individuals the phonological representation of a written word appears to be computed automatically (through an implicit "sounding out" or "letter-sound" conversion process) when a written word is perceived. This derived phonological information can influence the time course of lexical access, making word recognition slower for words that have an unusual letter-sound correspondence, particularly if these words appear infrequently in print (e.g., "yacht"). Despite this slowing, the correct word is typically accessed, indicating that readers cannot be relying solely on letter-sound correspondences in accessing the meaning of written words.

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