Individual uniformity in phonetic imitation: Assessing the stability of individual variability across features and tasks

Extensive individual variability has been reported in both spontaneous phonetic convergence and in explicit phonetic imitation tasks. This work tests the consistency of these individual patterns: are some individuals just globally more imitative, showing greater-than-average imitation regardless of the specific phone being imitated, and regardless of the type of imitation, or does an individual’s extent of imitation depend heavily on the phonetic content or the type of task? We examine the stability of individual variability in imitation of two types of subphonemic differences (VOT of voiceless stops and F2 of the vowels /æ/ and /u/), in two types of imitation tasks (implicit and explicit). We found that individuals' degree of imitation was significantly related across different phones within the same class (e.g., imitation of /p/ vs. /t/) in both implicit and explicit imitation tasks, but that individuals' degree of imitation of phones from different classes (e.g., imitation of stops vs. vowels) was only related in explicit, but not implicit, imitation. Findings are consistent with the idea that general cognitive or personality traits may govern individual variability in explicit imitation, but challenge the idea that they play any measurable role in predicting individual variability in implicit or spontaneous imitation. We also found a weak but significant correspondence between individual performance on the implicit and explicit imitation tasks, providing evidence that the two tasks rely on shared mechanisms, as well as a significant relationship between discrimination performance and explicit, but not implicit, imitation.