Clarity in communication: “Clear” speech authenticity and lexical neighborhood density effects in speech production and perception

Abstract

Speech produced in the context of real or imagined communicative difficulties is characterized by hyperarticulation. Phonological neighborhood density (ND) conditions similar patterns in production: Words with many neighbors are hyperarticulated relative to words with fewer; Hi ND words also show greater coarticulation than Lo ND words [e.g., Scarborough, R. (2012). "Lexical similarity and speech production: Neighborhoods for nonwords," Lingua 122(2), 164-176]. Coarticulatory properties of "clear speech" are more variable across studies. This study examined hyperarticulation and nasal coarticulation across five real and simulated clear speech contexts and two neighborhood conditions, and investigated consequences of these details for word perception. The data revealed a continuum of (attempted) clarity, though real listener-directed speech (Real) differed from all of the simulated styles. Like the clearest simulated-context speech (spoken "as if to someone hard-of-hearing"-HOH), Real had greater hyperarticulation than other conditions. However, Real had the greatest coarticulatory nasality while HOH had the least. Lexical decisions were faster for words from Real than from HOH, indicating that speech produced in real communicative contexts (with hyperarticulation and increased coarticulation) was perceptually better than simulated clear speech. Hi ND words patterned with Real in production, and Real Hi ND words were clear enough to overcome the dense neighborhood disadvantage.

Lexically conditioned phonetic variation in motherese: age-of-acquisition and other word-specific factors in infant- and adult-directed speech

“…Although these effects might seem contrary to the increased coarticulation in IDS (Andruski and Kuhl 1996), and in later-acquired words in IDS in particular (in the current study), they could in fact be interpreted as having a similar goal: to provide better information about the segments in a word. More extreme vowel articulation and more canonical consonant allophones straightforwardly provide better information about the identity of these segments; increased (consonant-to-vowel) coarticulation provides temporally-distributed and predictive information about the identity of the upcoming consonant (e.g., Ali et al 1971;Lahiri and MarslenWilson 1991;Beddor et al 2013;Scarborough and Zellou 2013). Thus, the confluent increase in degree of contextual nasalization (from consonant to vowel) and more extreme vowel articulation in ostensibly harder, later-acquired words in IDS are not incompatible and may even serve a similar purpose.…”

“…Recall that prior studies have found evidence of consistent ND effects on hyperarticulation and coarticulation in laboratory speech, elicited as standard citation form speech or as explicitly (adult) listener-directed (e.g., Wright 2003;Munson and Solomon 2004;Scarborough 2013;Scarborough and Zellou 2013).…”

“…In fact, explicitly instructing talkers to speak 'clearly', relative to 'conversational' or 'citation' speech, produces a range of acousticphonetic adjustments, including increased intensity (Picheny et al 1986), longer segment durations and slower speech rate (e.g., Picheny et al 1986;Bradlow et al 2003), larger F 0 range (Bradlow et al 2003), and enhancement of higher frequency ( > 1000 Hz) components in the long-term spectrum (Krause and Braida 2003). Prior studies have also shown more segmentally-focused spectral effects in clear speech in the form of vowel hyperarticulation or vowel space expansion (Picheny et al 1986;Lindblom 1989, Moon andLindblom 1994;Bradlow et al 2003;Krause and Braida 2003;Scarborough and Zellou 2013), as well as maintained or increased consonant-to-vowel coarticulation (Mathies et al 2001;Bradlow 2002;Scarborough and Zellou 2013). Indeed, these clear speech modifications yield speech that is more intelligible than 'conversational' speech (Picheny et al 1986;Bradlow et al 1996).…”

“…Gahl et al 2012). For instance, the hyperarticulation in high-ND words has been interpreted as serving to mitigate lexical difficulty, since the hyperarticulated vowels would render the high-ND words more distinguishable from their competitors (Wright 2003;Scarborough 2013;Scarborough and Zellou 2013). The increase in coarticulation that cooccurs with increased hyperarticulation in high ND words suggests that the coarticulation too may serve to improve the perceptibility of these words (Scarborough 2013).…”

“…Speech exhibiting hyperarticulated vowels has been shown to be more intelligible than speech with less hyperarticulated vowels (Bradlow et al 1996). Furthermore, words produced with hyperarticulation and the greatest increased nasal coarticulation, as found in listener-directed clear speech, are perceived more quickly than words produced with hyperarticulation but decreased nasal coarticulation (Scarborough and Zellou 2013). Also, earlier onset of anticipatory nasality in a vowel preceding a nasal consonant speeds lexical identification (Beddor et al 2013).…”