Redundancy in the speech signal helps amusics perceive prosody

Abstract

Speech is information dense, rapidly conveying segmental, semantic, syntactic, and prosodic information through the manipulation of a small handful of acoustic cues. As a result, impaired perception of one of these cues could impede acquisition of linguistic structure at multiple levels. For example, impaired perception of temporal patterns has been linked to developmental language delays. However, auditory impairments do not necessarily lead to language delays, suggesting that some people are able to compensate for difficulties with sound perception. This may be due to the perceptual redundancy of speech—the fact that multiple auditory dimensions often convey the same linguistic information. We tested this hypothesis by examining prosody perception in individuals with amusia, i.e., severe difficulties with the perception of musical melodies. First, we find that amusics show decreased functional connectivity between auditory and motor cortices during speech perception, suggesting that amusia is a domain-general deficit in pitch perception stemming from decreased auditory-motor connectivity. Second, we find that amusics compensate for their impairment by relying upon preserved perceptual abilities, suggesting that redundancy makes speech somewhat robust to individual differences in perceptual skill.