Abstract
A prominent pitch accent is known to trigger immediate contrastive interpretation of the accented referential expression. Previous experimental demonstrations of this effect, where [L+H* unaccented] contours led to an increase in earlier responses than [H* !H*] contours in contrastive context, may have benefited from the use of laboratory speech with stylized, homogenous pitch contours as well as data collected from a uniform participant group—college students. The present study tested visitors to a science museum, who better represent the general public, comparing lab and spontaneous speech to replicate the contrast-evoking effect of prominent pitch accent. Across two eye-tracking experiments where participants followed spoken instructions to decorate Christmas trees, spontaneous two-word [L+H* unaccented] contours led to faster eye-movements to contrastive ornament sets than [H* !H*] contours with no delay as compared to lab speech. The differences in the fixation functions were overall smaller than those in a previous study that used clear lab speech in richer contexts. Detailed acoustic analyses indicated that the lab speech tune types were distinguishable by any of several independent F0 measures on the adjective and by F0 slope. In contrast, no single phonetic measure on the spontaneous speech adjective distinguished between tune types, which were best classified according to independent noun-based measures. However, a non-linear combination of the adjective measures was shown to be equal to the noun measures in distinguishing between the [H* !H*] and [L+H* unaccented] tunes. The eye-movement data suggest that naive listeners were comparably sensitive to both lab and spontaneous prosodic cues on the adjective and made anticipatory eye-movements accordingly.
Highlights
Experiment 1 Data from twenty-eight participants were excluded from the analysis due to frequent track loss (15), calibration problems (4), other system failure (3), and other reasons such as a participant being a non-native speaker of American English, color blind, under age, etc. (4), leaving 66 participants in each speech type group
Experiment 1 confirmed the predicted eye-movement patterns that suggest the contrastive interpretation of the [L+H* unaccented] contours in both lab speech and spontaneous speech: In the Contrastive sequences, the looks to the target ornament cell increased faster with the [L+H* unaccented] contours than with the [H* !H*] contours, while in the NonContrastive sequences, [L+H* unaccented] contours led to more incorrect looks to the previously mentioned ornament set than the [H* !H*] contours
The overall timing of fixations tended to be faster for the spontaneous speech group than for the lab speech group
Summary
Stimuli and participants Laboratory investigation of speech perception or comprehension is often bound to two types of invariance: One comes by choice and another as a practical constraint. Stimuli are carefully handpicked such that all items in an experimental condition conform to the intended sound pattern and differ from the items of a comparison condition in a consistent manner. Any given item from a particular condition should. Ito et al: Allophonic tunes of contrast sound different from any given item from the comparison condition. In order to clear this non-trivial requirement, researchers often ask highly trained laboratory personnel to produce the stimuli (or synthesize/artificially modulate particular acoustic parameters of natural speech) for their experiments
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