Perceptual parsing of acoustic consequences of velum lowering from information for vowels

Abstract

Three experiments were designed to investigate how listeners to coarticulated speech use the acoustic speech signal during a vowel to extract information about a forthcoming oral or nasal consonant. A first experiment showed that listeners use evidence of nasalization in a vowel as information for a forthcoming nasal consonant. A second and third experiment attempted to distinguish two accounts of their ability to do so. According to one account, listeners hear nasalization in the vowel as such and use it to predict that a forthcoming nasal consonant is nasal. According to a second, they perceive speech gestures and hear nasalization in the acoustic domain of a vowel as the onset of a nasal consonant. Therefore, they parse nasal information from a vowel and hear the vowel as oral. In Experiment 2, evidence in favor of the parsing hypothesis was found. Experiment 3 showed, however, that parsing is incomplete.Theories of speech perception differ in their characterization of phonological categories and of the stimulus information that listeners are presumed to use to detect the phonological properties ofspoken utterances. In some theoretical accounts, phonological categories are cognitive categories in the mind; listeners identify intended phonological properties of an utterance from associated acoustic and, sometimes, optical cues. The results of initial stages of auditory (visual) analysis of a speech stimulus are mapped onto the mental phonological categories. In other accounts, phonological categories are gestural in nature; listeners identify the phonological properties of utterances by extracting acoustic and, sometimes, optical information about them that is available because gestural causes have specifying acoustic and, sometimes, optical consequences.As distinct as these views are conceptually, they have proven difficult to distinguish experimentally. Generally, researchers agree on what serves as acoustic information for the phonological properties of words. They disagree on what the acoustic information serves as information for: abstract, mental categories or phonological actions of the vocal tract.One approach that we have taken to try to distinguish the views experimentally has been to look closely at listeners' modes of attention to the acoustic speech signal. Although researchers generally agree on what serves as acoustic information, there may be some cases in which listeners who are attempting to extract information about gestures should differ in their mode of attention to the

The role of stimulus cross-splicing in an event-related potentials study. Misleading formant transitions hinder automatic phonological processing

“…Focussing on coarticulatory effects between vowels and obstruents, several studies investigated the impact of F2 transitions and acoustic parameters of the obstruents such as, for example, the spectrum of the friction noise (among many others Harris 1958;Whalen, 1983Whalen, , 1984Wagner et al, 2006;Nowak, 2006), or the burst (for example, Cho and McQueen, 2006;Smits et al, 1996). Furthermore, coarticulatory information has been manipulated by means of cross-splicing to behaviorally investigate the impact of phonological processes such as assimilations on speech processing (e.g., Fowler and Brown, 2000;Gow, 2001;Mitterer and Blomert, 2003;Gaskell and Snoeren, 2008;Hwang et al, 2010), or to investigate the impact of phonetic analysis on higher-order processes such as lexical access (Whalen, 1991).…”

Sensorimotor adaptation affects perceptual compensation for coarticulation

“…One example of the coarticulated nature of speech can be found in vowel-consonant coarticulation; in English, a vowel preceding a nasalized consonant will also tend to be nasalized (Bell-Berti and Krakow, 1991). Both behavioral (Fowler and Brown, 2000) and neuroimaging experiments (Flagg et al, 2006) reveal that English listeners are sensitive to this nasalization as an indicator of an upcoming nasal consonant. The ability of listeners to recognize segments as the same under such varying conditions, and to utilize such cues, was a primary factor leading to the characterization of representations involved in speech perception as ultimately articulatory in nature (Liberman and Mattingly, 1985).…”

“…For example, in the study by Fowler and Brown (2000) on the perception of vowel-nasal consonant sequences, listeners were found to perceive a nasalized vowel as less nasal if it was followed by a nasal consonant compared to when it was followed by an oral consonant. Perceivers perceptually "compensated" for the coarticulatory effects of the nasal consonant on the preceding vowel by attributing acoustic information from one segment to the following segment.…”

Phonological knowledge in compensation for native and non-native assimilation

“…Gow (2001Gow ( , 2002aGow ( , 2003 proposed a language independent processing mechanism called Feature Cue Parsing to handle both coarticulation and systematic phonological variation. In this mechanism, temporally distributed acoustic cues of feature values are grouped and integrated into segmentally aligned phonetic features (see also Fowler 1996;Fowler and Brown 2000). Gow's specific proposal is that feature parsing can account both for coarticulatory compensation and compensation for phonological assimilation, at least in the (frequent) cases where assimilation is not complete.…”