Lecture by Christopher Heffner, PhD: Individual Differences
in Phonetic Plasticity: Rate, Accent, and Learning

Speech understanding requires constant adjustment. This can be seen most radically when encountering new speech sound tokens in a second language, where categorizing non-native sounds requires learning. Yet adjustment to phonetic categories can be observed even within a native language, where tolerating variation between talkers in speech rate or in accent requires adaptation. Though non-native and native speech perception share similarities, it is unclear whether they rely on common cognitive and neural resources. In the present study, we explore individual differences in each process in behavior, then compare these differences in behavior to neural (structural, DTI, and resting-state functional) measures. In the end, we find interrelationships in performance on three of our measures of phonetic plasticity: explicit learning, accent adaptation, and rate adaptation, but not with incidental phonetic learning. Better learners of non-native tokens in explicit tasks were also better adapters. This suggests that learning and adaptation may depend on shared behavioral plasticity. These differences are related to differences in brain structure, particularly in auditory temporal areas.