Words are more than the sum of their parts: evidence for detrimental effects of word-level information in alexia.

The effects of sequential letter presentation on reading were investigated with both normal readers and an alexic patient. Normal readers showed longer naming latencies when words were presented letter-by-letter than when all the letters were presented simultaneously. In contrast, naming latencies for the alexic reader were shorter when words were presented letter-by-letter (error rates did not differ for the patient and the controls). Further experiments provided evidence for the patient being abnormally affected by lateral masking between stimuli, though she could access phonology from subword functional spelling units. The experiments demonstrate that, for alexic and normal readers alike, words are more than the sum of their individual letters; however, for normal readers a supra-letter reading strategy is useful whereas it can be detrimental in alexia.