Short-term retention of learning after rapid adaptation to native and non-native speech

Non-native, accented speech spoken by unfamiliar talkers can be challenging to recognize, but rapid improvements in perception are often observed after a short period of exposure. However, it is not clear whether these improvements are retained over multiple sessions. Stimulus variability facilitates learning for non-native speech, so it is possible it may also induce increased retention of learning for speech produced with an unfamiliar accent. In this paper, we conduct a retrospective analysis of a dataset well suited to examine learning of non-native English speech on both a within-session and across-session basis. During data collection, participants completed a protocol involving recognition of matrix sentences recorded by native and non-native talkers with different first languages. Listeners completed the protocol in a self-paced approach, including 15 blocks of 50 trials over 4-7 days, separated by an average of 1-2 days. Learning was strongest within the first day, and improvements were retained at subsequent test sessions. The pace of learning was faster for stimuli produced by native speakers of English as compared to non-native English speakers.