Tailored perception: Individuals’ speech and music perception strategies fit their perceptual abilities.

Abstract

Perception involves integration of multiple dimensions that often serve overlapping, redundant functions, for example, pitch, duration, and amplitude in speech. Individuals tend to prioritize these dimensions differently (stable, individualized perceptual strategies), but the reason for this has remained unclear.Here we show that perceptual strategies relate to perceptual abilities. In a speech cue weighting experiment (trial N ϭ 990), we first demonstrate that individuals with a severe deficit for pitch perception (congenital amusics; N ϭ 11) categorize linguistic stimuli similarly to controls (N ϭ 11) when the main distinguishing cue is duration, which they perceive normally. In contrast, in a prosodic task where pitch cues are the main distinguishing factor, we show that amusics place less importance on pitch and instead rely more on duration cues-even when pitch differences in the stimuli are large enough for amusics to discern. In a second experiment testing musical and prosodic phrase interpretation (N ϭ 16 amusics; 15 controls), we found that relying on duration allowed amusics to overcome their pitch deficits to perceive speech and music successfully. We conclude that auditory signals, because of their redundant nature, are robust to impairments for specific dimensions, and that optimal speech and music perception strategies depend not only on invariant acoustic dimensions (the physical signal), but on perceptual dimensions whose precision varies across individuals. Computational models of speech perception (indeed, all types of perception involving redundant cues e.g., vision and touch) should therefore aim to account for the precision of perceptual dimensions and characterize individuals as well as groups.

Altered functional connectivity during speech perception in congenital amusia

“…Follow-up post-hoc testing indicated that performance in the Combined condition (with pitch and duration cues simultaneously present) was more accurate than either Pitch-Alone (T(84) = 2.3, p = 0.02) or Time-Alone (T(84) = 2.1, p = 0.03), a result that was also predicted and which replicates the behavioral findings in Jasmin et al (2019a).…”

“…Overall, proportion correct across amusia and control groups was matched (main effect of Group, F(1,84) = 0.16, p = 0.69), interaction of Group by Condition (F(2,84) = 0.374, p = 0.96). This lack of interaction was predicted based on previous results obtained from a similar paradigm using out-of-scanner data but from the same participants (Jasmin et al, 2019a). There was a main effect of condition (F(2,84) = 3.32, p = 0.04.…”

“…As mentioned, the acoustic speech signal carries multiple co-occurring acoustic dimensions (e.g. roughly described as pitch, duration, and amplitude), which often provide redundant cues to disambiguate a linguistic category (Patel, 2014;Winter, 2014;Jasmin et al, 2019a). Individuals with typical pitch perception have learned through a lifetime of experience with speech acoustics that vocal pitch is a useful and reliable cue.…”

“…Given that amusics have unreliable perception of and memory for pitch and have low pitch cue weights during language processing (Jasmin et al, 2019a), do they also exhibit correspondingly decreased functional connectivity between regions typically found to be involved in pitch processing and frontal regions associated with speech and language? Here we set out to answer these questions.…”

“…The benefit of this approach is that any set of regions could emerge, not only ones reported in previous literature. Crucially, task performance was matched between the groups (based on prior behavioural testing (Jasmin et al, 2019a), ensuring that any neural differences did not simply represent an inability to perform the task.…”