Spoken word recognition in quiet and in noise by native and non-native listeners: Effects of age of immersion and vocabulary size

In spoken word recognition, high-frequency words with few neighbors and less frequently occurring minimal pair neighbors (lexically easy words) are recognized more accurately than low-frequency words with many and more frequently occurring neighbors (lexically hard words). Bradlow and Pisoni (1999) found a larger easy hard word effect for non-native than native speakers of English. The present study extends this work by specifically comparing word recognition by non-native listeners with either earlier or later ages of immersion in an English-speaking environment to that of native English speakers. Listeners heard six lists of 24 words, each composed of 12 lexically easy and 12 lexically hard words in an open-set word identification task. Word lists were presented in quiet and in moderate noise. A substantially larger easy-hard word effect was obtained only for the later learners, but a measure of oral vocabulary size was significantly correlated with performance for the non-native listener groups only. Thus, the increased easy-hard word effect for non-native listeners appears to be explained as an effect of phonetic proficiency and/or vocabulary size on the structure of the lexical neighborhoods.