The effects of "neighborhood size" in reading and lexical decision

The effects of neighborhood size ("N")--the number of words differing from a target word by exactly 1 letter (i.e., "neighbors")--on word identification was assessed in 3 experiments. In Experiments 1 and 2, the frequency of the highest frequency neighbor was equated, and N had opposite effects in lexical decision and reading. In Experiment 1, a larger N facilitated lexical decision judgments, whereas in Experiment 2, a larger N had an inhibitory effect on reading sentences that contained the words of Experiment 1. Moreover, a significant inhibitory effect in Experiment 2 that was due to a larger N appeared on gaze duration on the target word, and there was no hint of facilitation on the measures of reading that tap the earliest processing of a word. In Experiment 3, the number of higher frequency neighbors was equated for the high-N and low-N words, and a larger N caused target words to be skipped significantly more and produced inhibitory effects later in reading, some of which were plausibly due to misidentification of the target word when skipped. Regression analyses indicated that, in reading, increasing the number of higher frequency neighbors had a clear inhibitory effect on word identification and that increasing the number of lower frequency neighbors may have a weak facilitative effect on word identification.