The lexical quality hypothesis assumes that skilled readers rely on high quality lexical representations that afford autonomous lexical retrieval and reduce the need to rely on top-down context. This experiment investigated this hypothesis by comparing the performance of adults classified on reading comprehension and spelling performance. 'Lexical experts', defined by above average performance on both measures, were compared with individuals who are good readers/poor spellers, poor readers/good spellers, or poor on both measures. Sentences finishing with a homograph (e.g., She danced all night at the ball) were followed by a probe word and participants had to decide whether it had occurred in the sentence. Critical probe words were related to either the sentence-congruous or the sentence-incongruous meaning of the homograph (e.g., waltz vs. throw). Lexical experts showed less interference from related probes than the other groups. When the sentences were presented at fast rates, poorer spellers showed interference for sentence-congruous but not sentence-incongruous probes. However, at slower presentation rates, all groups showed equivalent interference for both types of probes. The results support the lexical quality hypothesis by showing that high quality lexical representations, indexed by better spelling, are associated with reduced reliance on sentence context.

Repetition blindness (RB) refers to the failure to report both occurrences of a repeated item in a series of rapidly presented visual stimuli. For instance, the sentence When she spilled the ink there was ink all over, presented word by word at a rate of around 100 msec/word, may be reported as "When she spilled the ink there was all over" (Kanwisher, 1987), even though the sequence is nongrammatical. RB also occurs for repeated items in lists of words and pictures (see Coltheart, 1999, for reviews), but the phenomenon is particularly striking in sentences, where its occurrence generally fails to respect the constraints of coherence or syntax. This has contributed to accounts that locate the phenomenon at the lexical level, rather than at the later stages of memory and recall. In the experiments reported here, novel variations of the standard RB sentence-processing paradigm were used to shed further light on the relative contribution of bottom-up and top-down processes to RB and, more generally, on the role of lexical activation in sentence processing. Kanwisher's (1987) original interpretation of RB drew upon the distinction between types and tokens. Reporting the identity of an item in a stimulus sequence requires not only activation of the existing representation of the item's type representation in memory, but also creation of a token representing the occurrence of that type in the processing episode (Kahneman & Treisman, 1984). For example, the conceptual processing required to build a coherent structure from the words of a sentence requires more than activation of word types in lexical memory; comprehension and recall depend on establishing tokens of these words and the sentential relationships between them in that specific sentence. In this framework, RB is the consequence of a perceptual limitation that impairs the rapid creation of separate tokens for two occurrences of the type. Type-Token Accounts of RBThere are two major variants of this type-token account that propose different sources for RB. According to the type refractoriness hypothesis, RB is due to the activation dynamics of type nodes, rather than to a problem with token formation or binding. The representation of a particular stimulus undergoes a period of reduced sensitivity immediately after firing, by analogy with the refractoriness of neurons. Accordingly, if the stimulus appears twice in close succession, the second occurrence may be unable to increase the node's activation enough to be recognized or induce a response. The second class of models attributes RB to problems in token individuation. Even though the two separate occurrences are both "recognized" at the type level, formation of a second token from a single type is briefly inhibited after the first token is individuated (e.g., Kanwisher, 1987).The type refractoriness hypothesis has been formalized in dynamical models based on a signal detection approach that implement a "rudimentary form of adaptation" (Bavelier & Jordan, 1992, p. 883). Bavelier and Jordan's model assumes that ...

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