We examined how phonological competition effects inspoken word recognition change with word length. Cohorteffects (competition between words that overlap at onset) arestrong and easily replicated. Rhyme effects (competitionbetween words that mismatch at onset) are weaker, emergelater in the time course of spoken word recognition, and aremore difficult to replicate. We conducted a simple experimentto examine cohort and rhyme competition using monosyllabicvs. bisyllabic words. Degree of competition was predicted byproportion of phonological overlap. Longer rhymes, withgreater overlap in both number and proportion of sharedphonemes, compete more strongly (e.g., kettle-medal [0.8overlap] vs. cat-mat [0.67 overlap]). In contrast, long andshort cohort pairs constrained to have constant (2-phoneme)overlap vary in proportion of overlap. Longer cohort pairs(e.g., camera-candle) have lower proportion of overlap (inthis example, 0.33) than shorter cohorts (e.g., cat-can, with0.67 overlap) and compete more weakly. This finding hasmethodological implications (rhyme effects are less likely tobe observed with shorter words, while cohort effects arediminished for longer words), but also theoreticalimplications: degree of competition is not a simple functionof overlapping phonemes; degree of competition isconditioned on proportion of overlap. Simulations withTRACE help explicate how this result might emerge.

What determines degree of competition among phonologicallysimilar words? One proposal is that proportion of overlappredicts competition independently of word length. We arguethat proportion of overlap may provide descriptive adequacy,but does not provide an explanation. We show that TRACEcorrectly predicts patterns previously attributed to proportionof overlap. In additional simulations, with independentmanipulations of word length and proportion of overlap,proportion of overlap fails to predict the full pattern of results.We discuss how competition dynamics in TRACE modulatecompetition as word length and proportion of overlap change.These results have implications for theories of human spokenword recognition, and will motivate experiments to test thesenew TRACE predictions.