Speaking rate normalization with and without segregation of simultaneous context sentences

Speech perception is shaped by acoustic properties of earlier sounds influencing recognition of later speech sounds. For example, when a context sentence is spoken at a faster rate, the following target word (varying from “deer” to “tier”) is perceived as “tier” (longer VOT) more often; when a slower context sentence is spoken, the following target word is perceived as “deer” (shorter VOT) more often. This is known as a temporal contrast effect (TCE, a.k.a. speaking rate normalization). Recently, Bosker, Sjerps, and Reinisch (2020 Scientific Reports) concluded that selective attention (to one of two simultaneous talkers) had no impact on TCEs. However, their paradigm was not an ideal test of this question; the voices heard were different talkers presented to each ear, and thus relatively easy to perceptually separate. Here, on each trial, the same talker spoke one sentence to both ears (no segregation), two sentences simultaneously to both ears (poor segregation), or a different sentence to each ear (easier segregation). Fast or slow context sentences preceded target words varying from “deer” to “tier.” TCE magnitudes were similar across all presentation modes. Results are consistent with the claims set forth by Bosker et al. – TCEs are automatic and low-level, not modulated by selective attention.