Effects of cognitive workload on speech production: Acoustic analyses and perceptual consequences

Abstract

The present investigation examined the effects of cognitive workload on speech production. Workload was manipulated by having talkers perform a compensatory visual tracking task while speaking test sentences of the form "Say hVd again." Acoustic measurements were made to compare utterances produced under workload with the same utterances produced in a control condition. In the workload condition, some talkers produced utterances with increased amplitude and amplitude variability, decreased spectral tilt and F0 variability and increased speaking rate. No changes in F1, F2, or F3 were observed across conditions for any of the talkers. These findings indicate both laryngeal and sublaryngeal adjustments in articulation, as well as modifications in the absolute timing of articulatory gestures. The results of a perceptual identification experiment paralleled the acoustic measurements. Small but significant advantages in intelligibility were observed for utterances produced under workload for talkers who showed robust changes in speech production. Changes in amplitude and amplitude variability for utterances produced under workload appeared to be the major factor controlling intelligibility. The results of the present investigation support the assumptions of Lindblom's ["Explaining phonetic variation: A sketch of the H&H theory," in Speech Production and Speech Modeling (Klewer Academic, The Netherlands, 1990)] H&H model: Talkers adapt their speech to suit the demands of the environment and these modifications are designed to maximize intelligibility.

Recognition of spoken words by native and non-native listeners: Talker-, listener-, and item-related factors

“…These studies, and many others, have provided a great deal of new information about the way in which individual talkers modify and adjust their articulatory patterns to accommodate situational demands. However, aside from establishing that the "clear" speech style does indeed provide an intelligibility advantage over "conversational" speech (Picheny et al, 1985), considerably less attention has been paid to the direct perceptual consequences, from the listener's point of view, of different styles of speech (see Summers et al, 1988;Lively et al, 1993). Important questions that remain to be answered are: (1) Which of the clear speech transformations are most effective in aiding speech communication?…”

Modeling hyperarticulate speech during human-computer error resolution

“…Even young preschool children actively adapt their speech to accommodate perceived listener characteristics (Shatz and Gelman, 1973). Systematic speech modifications also have been observed in noisy environments (Hanley and Steer, 1949;Junqua, 1993;Schulman, 1989;Summers et al, 19881, in environments involving heavy workload or that precipitate psychological stress (Brenner et al, 1985;Lively et al, 1993;Tolkmitt and Scherer, 1986;Williams and Stevens, 19691, and when speakers are asked to "speak clearly" in laboratory settings Butterfield, 1990, 1991;Moon, 1991;Moon and Lindblom, 1994).…”

“…In addition, the adaptations observed in Lombard speech have sometimes included variability due to gender effects (Junqua, 1993). Under conditions of high workload, speakers typically increase both amplitude and variability in amplitude, while simultaneously speaking at a faster rate and with decreased pitch range (Lively et al, 1993). When speakers are stressed by their environment, noteworthy adaptations include an increase in fundamental frequency and change in pitch variability (Brenner et al, 1985;To&mitt and Scherer, 1986;Williams and Stevens, 1969).…”

“…For example, in a variety of studies involving normal and impaired listeners, the following hyper-clear speech characteristics have been associated with improved intelligibility -increased duration of speech segments and pauses, slower speaking rate, increased duration of vowels and clearer differentiation of the vowel space with respect to formant values, more distinct VOT distributions for voiced and voiceless consonants, increased amplitude and reduced variability in amplitude, increased consonant-to-vowel amplitude ratio, and increased pitch and expansion of pitch range (Bond and Moore, 1994;Chen, 1980;Cutler and Butterfield, 1990;Gordon-Want, 1987;Lively et al, 1993;Moon, 1991;Payton et al, 1994;Picheny et al, 1985;Uchanski et al, 1996). These studies confirm that listeners can recover lexical content more successfully when speech is adapted toward the hyperarticulate end of the spectrum, rather than being conversational.…”

Team Communication as a Collaborative Process

“…However, other studies have suggested that increased disfluency rate may be due to coordination processes rather than planning difficulties associated with workload (Swerts, 1998;Bortfeld et al, 2001;Clark and Krych, 2004). In terms of speech, Lively et al (1993) found that utterance length decreases with workload, but more recent work by Khawaja et al (2012) found increases in sentence length as well as in speech rate, words indicating disagreement, and the usage of plural personal pronouns (e.g., "we" and "us"). Finally, Urban et al (1995) found that under high workload, effective teams asked fewer questions, made fewer requests, and made fewer responses to requests.…”