The role of bigram frequency in the perception of words and nonwords.

Adult subjects decided whether strings of four, five, or six letters formed words or nonwords. Words and nonwords were equally probable stimuli, and there were equal numbers of stimuli of high and low mean bigram frequency. Half the words were common and half occurred rarely i[~ printed English. Mean bigram frequency had no effect on subjects' response times for common words and for nonwords, but the reaction times for rare words were significantly longer for words of high mean bigram frequency than for words of low mean bigram frequency. This result may be accounted for by a modification of Rumelhart and Siple's (1974) model of word perception to include the mapping of simple features to units which correspond to common spelling patterns.