Redundancy makes music and speech robust to individual differences in perception

Abstract

In speech, linguistic information is conveyed redundantly by many simultaneously present acoustic dimensions, such as fundamental frequency, duration and amplitude. Listeners show stable tendencies to prioritize these acoustic dimensions differently, relative to one another, which suggests individualized speech perception strategies. However, it is unclear what drives these strategies, and more importantly, what impact they have on diverse aspects of communication. Here we show that such individualized perceptual strategies can be related to individual differences in perceptual ability. In a cue weighting experiment, we first demonstrate that individuals with a severe pitch perception deficit (congenital amusics) categorize linguistic stimuli similarly to controls when their deficit is unrelated to the main distinguishing cue for that category (in this case, durational or temporal cues). In contrast, in a prosodic task where pitch-related cues are typically more informative, amusics place less importance on this pitch-related information when categorizing speech. Instead, they relied more on duration information. Crucially, these differences in perceptual weights were observed even when pitch-related differences were large enough to be perceptually distinct to amusic listeners. In a second set of experiments involving musical and prosodic phrase interpretation, we found that this reliance on duration information allowed amusics to overcome their perceptual deficits and perceive both speech and music successfully. These results suggest that successful speech - and potentially music - comprehension is achieved through multiple perceptual strategies whose underlying weights may in part reflect individuals perceptual abilities.