Lexical recovery from extinction: Interactions between visual form and stored knowledge modulate visual selection

The effects of lexical knowledge on extinction were examined in a patient with bilateral parietal lesions and left extinction under double simultaneous stimulation: GK. GK was bilaterally presented with two letters that could form either a word or a nonword. In Experiments 1-3, the task was to identify each letter. GK showed better identification of left-side letters in words than in nonwords, whilst the identification of left-side letters in nonwords was worse than that of single letters presented in the same spatial positions (i.e., there was a word superiority effect under conditions in which extinction occurred). This lexical effect on completely correct responses tended to be larger for words with lower-case letters (Experiments 2 and 3) than for words with upper-case letters (Experiment 1). Different results arose when detection was measured. When letters could group by proximity and common contrast polarity, no word superiority effect was apparent. However, a word superiority effect re-emerged when low-level grouping was reduced by using letters with opposite contrast polarity (one white and one black on a grey background). The results are discussed in terms of the impact of different factors on selection in detection and identification tasks, and in terms of the modulatory roles of familiar form and stored knowledge on visual selection.