Combined effects of form- and meaning-based predictability on perceived clarity of speech.

Abstract

The perceptual clarity of speech is influenced by more than just the acoustic quality of the sound; it also depends on contextual support. For example, a degraded sentence is perceived to be clearer when the content of the speech signal is provided with matching text (i.e., form-based predictability) before hearing the degraded sentence. Here, we investigate whether sentence-level semantic coherence (i.e., meaning-based predictability), enhances perceptual clarity of degraded sentences, and if so, whether the mechanism is the same as that underlying enhancement by matching text. We also ask whether form- and meaning-based predictability are related to individual differences in cognitive abilities. Twenty participants listened to spoken sentences that were either clear or degraded by noise vocoding and rated the clarity of each item. The sentences had either high or low semantic coherence. Each spoken word was preceded by the homologous printed word (matching text), or by a meaningless letter string (nonmatching text). Cognitive abilities were measured with a working memory test. Results showed that perceptual clarity was significantly enhanced both by matching text and by semantic coherence. Importantly, high coherence enhanced the perceptual clarity of the degraded sentences even when they were preceded by matching text, suggesting that the effects of form- and meaning-based predictions on perceptual clarity are independent and additive. However, when working memory capacity indexed by the Size-Comparison Span Test was controlled for, only form-based predictions enhanced perceptual clarity, and then only at some sound quality levels, suggesting that prediction effects are to a certain extent dependent on cognitive abilities. (PsycINFO Database Record

Hearing Impairment and Perceived Clarity of Predictable Speech

“…We tend to hear what we expect to hear-this is a common observation and recently supported by data showing that the perceived clarity of degraded speech is enhanced by both predictability based on form (i.e., phonological/lexical) at the word level and on meaning (i.e., semantic) at the sentence level (Signoret et al 2018). For individuals with hearing impairment (HI) who may struggle particularly hard to understand degraded speech, the potential support of such predictability could be invaluable.…”

“…For individuals without HI, this effect, known as the "pop-out effect," has been investigated extensively (Davis et al 2005;Davis & Johnsrude 2007;Hervais-Adelman et al 2011;Wild et al 2012), whereas it has not, to our knowledge, been reported whether individuals with HI experience the pop-out effect. For individuals without HI, presenting matching text only 200 msec before presenting a degraded spoken sentence, improves the perceived clarity of the sentence more than meaningless consonant strings (Wild et al 2012;Signoret et al 2018). This improvement in perceptual clarity is thought to be related to knowledge-based predictions about the phonological/lexical form of the upcoming word influencing upcoming speech processing (Sohoglu et al 2014;Signoret et al 2018).…”

“…For individuals without HI, presenting matching text only 200 msec before presenting a degraded spoken sentence, improves the perceived clarity of the sentence more than meaningless consonant strings (Wild et al 2012;Signoret et al 2018). This improvement in perceptual clarity is thought to be related to knowledge-based predictions about the phonological/lexical form of the upcoming word influencing upcoming speech processing (Sohoglu et al 2014;Signoret et al 2018). Perceptual clarity of degraded spoken sentences is also greater for sentences with high compared with low semantic coherence (Signoret et al 2018).…”

“…This improvement in perceptual clarity is thought to be related to knowledge-based predictions about the phonological/lexical form of the upcoming word influencing upcoming speech processing (Sohoglu et al 2014;Signoret et al 2018). Perceptual clarity of degraded spoken sentences is also greater for sentences with high compared with low semantic coherence (Signoret et al 2018). Such an improvement may be explained by the fact that knowledge-based predictions about the semantic meaning of the upcoming sentence facilitate processing by reducing the number of lexical candidates (Federmeier 2007).…”

Age-related differences in auditory cortex activity during spoken word recognition

“…Auditory cortex is positioned in a hierarchy of speech processing regions that include both ascending and descending projections (Davis and Johnsrude, 2007;Peelle et al, 2010a) . Auditory cortex is sensitive not only to changes in acoustic information, but also reflects top-down effects of expectation and prediction (Sohoglu et al, 2012;Wild et al, 2012;Signoret et al, 2018) . Thus, the observed age differences in auditory cortex may reflect differential top-down modulation of auditory activity in young and older adult listeners.…”