Word segmentation abilities across the adult lifespan: Evidence from younger and older adult bilinguals

Humans break down continuous speech into meaningful units by integrating multiple cues whose importance and relative weight change throughout development. We investigate whether segmentation abilities differ between younger and older adults while exploring how age of acquisition, proficiency, language use, and frequency of language switch determine Basque-Spanish younger and older bilinguals' use of lexico-semantic, morphosyntactic, and phonological information in L2 word segmentation. Younger and older L1Spanish-L2Basque bilinguals (n = 158) varying across the four dimensions of interest and a control group of L1Basque bilinguals (n = 63) were tested on a phoneme localization task in Basque. Age did not affect word segmentation in either group. Proficiency modulated performance of the L2Basque bilinguals, with the greatest accuracy gains in sentences containing all sources of information, followed by sentences containing only morphosyntactic and phonological cues, then sentences comprising only phonological information. Frequency of language switch and fluid intelligence were associated with better overall performance, though their contribution to explaining the variance was very small. Finally, natives benefited more than non-natives from lexico-semantic cues, and from morphosyntactic and phonological cues for word-initial targets. These findings suggest the stability of segmentation abilities across the adult lifespan, and evidence how different bilingual factors shape multiple cue use in L2 segmentation.