The spread and density of the phonological neighborhood can strongly influence the verbal transformation illusion.

When a recorded verbal stimulus repeats over and over, adaptation occurs and listeners hear competing forms. Reports of these "verbal transformations" (VTs) were obtained for 36 consonant-vowel (CV) syllables that varied both in frequency-weighted neighborhood density (ranging from 12.73 to 90.42) and in neighborhood spread [i.e., for 18 CVs, changes at either phoneme position could yield real words (spread = 2) while for the remaining 18 CVs, changes at only one position could yield words (spread = 1)]. The strength of the VT illusion, measured by the amount of time the stimuli were heard nonveridically during the 300-s repetition period, decreased substantially with both increasing neighborhood density [r=-0.74, F(1,34)=42.6, p<0.0001] and increasing spread [r=-0.75, F(1,34) = 44.1, p<0.0001]. Stepwise regression revealed that density and spread collectively accounted for approximately 70% of the variance in illusion strength [F(1,33)>=10.0, p<0.003 or better]. These effects are larger than, but generally consistent with, neighborhood effects obtained with other psycholinguistic tasks, and they suggest that VTs can provide a highly sensitive measure of lexical competition. [Work supported by NIH.].