Abstract
Language comprehension in noise can sometimes lead to mishearing, due to the noise disrupting the speech signal. Some of the difficulties in dealing with the noisy signal can be alleviated by drawing on the context – indeed, top-down predictability has shown to facilitate speech comprehension in noise. Previous studies have furthermore shown that strong reliance on the top-down predictions can lead to increased rates of mishearing, especially in older adults, which are attributed to general deficits in cognitive control in older adults. We here propose that the observed mishearing may be a simple consequence of rational language processing in noise. It should not be related to failure on the side of the older comprehenders, but instead would be predicted by rational processing accounts. To test this hypothesis, we extend earlier studies by running an online listening experiment with younger and older adults, carefully controlling the target and direct competitor in our stimuli. We show that mishearing is directly related to the perceptibility of the signal. We furthermore add an analysis of wrong responses, which shows that results are at odds with the idea that participants overly strongly rely on context in this task, as most false answers are indeed close to the speech signal, and not to the semantics of the context.
Highlights
Noisy Channel Model of Rational CommunicationWhen listening to speech, there are usually at least two sources of information available to decode the speaker’s message: There is the sensory information in the form of the acoustic speech signal, and there is contextual information that can help guide predictions (Boothroyd and Nittrouer, 1988; Nittrouer and Boothroyd, 1990)
We argue that the larger mishearing effect observed in older adults compared to younger adults may be a simple consequence of rational integration of the bottom-up and top-down information, i.e., that their performance is not necessarily an effect related to deficits in cognitive control, but may reflect a combination of stronger top-down expectations due to increased linguistic experience, and lower confidence in the bottom-up input, due to first experiences of hearing loss
To be able to distinguish between different accounts that explain the mishearing effect, we investigate the effect of noise on different types of speech sounds, and how these are affected by false hearing
Summary
Noisy Channel Model of Rational CommunicationWhen listening to speech, there are usually at least two sources of information available to decode the speaker’s message: There is the sensory information in the form of the acoustic speech signal, and there is contextual information that can help guide predictions (Boothroyd and Nittrouer, 1988; Nittrouer and Boothroyd, 1990). We rarely listen to other people speaking in perfectly quiet surroundings. There is a lot of noise going on in the background, for example, other people speaking, traffic noise, or working machinery. The noise puts extra strain on our speech comprehension processes, something especially older adults can struggle with (Li et al, 2004). Comprehenders take into account uncertainty in the perceptual input (for example, due to background noise). The noisy channel model (Shannon, 1949; Levy, 2008; Levy et al, 2009) proposes that language comprehension is a rational process, where we make use of all available sources of information. Bottom-up information from the speech signal is supplemented with
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