Abstract
Multi-talker conversations challenge the perceptual and cognitive capabilities of older adults and those listening in their second language (L2). In older adults these difficulties could reflect declines in the auditory, cognitive, or linguistic processes supporting speech comprehension. The tendency of L2 listeners to invoke some of the semantic and syntactic processes from their first language (L1) may interfere with speech comprehension in L2. These challenges might also force them to reorganize the ways in which they perceive and process speech, thereby altering the balance between the contributions of bottom-up vs. top-down processes to speech comprehension. Younger and older L1s as well as young L2s listened to conversations played against a babble background, with or without spatial separation between the talkers and masker, when the spatial positions of the stimuli were specified either by loudspeaker placements (real location), or through use of the precedence effect (virtual location). After listening to a conversation, the participants were asked to answer questions regarding its content. Individual hearing differences were compensated for by creating the same degree of difficulty in identifying individual words in babble. Once compensation was applied, the number of questions correctly answered increased when a real or virtual spatial separation was introduced between babble and talkers. There was no evidence that performance differed between real and virtual locations. The contribution of vocabulary knowledge to dialog comprehension was found to be larger in the virtual conditions than in the real whereas the contribution of reading comprehension skill did not depend on the listening environment but rather differed as a function of age and language proficiency. The results indicate that the acoustic scene and the cognitive and linguistic competencies of listeners modulate how and when top-down resources are engaged in aid of speech comprehension.
Highlights
Conversations with friends, co-workers, healthcare providers, and others often occur in noisy environments in which there are a number of different sound sources that could interfere with one’s ability to communicate effectively
One of the nonnative-English listeners had an Revised Speech Perception in Noise (R-SPIN) threshold of 22 dB signal-to-noise ratios (SNRs) in the virtual no separation condition. Since this value was more than three standard deviations above the mean for that group, this value was identified as an outlier and was replaced by the average R-SPIN threshold of the nonnative-English listeners group after excluding the outlier (6 dB SNR)2
The SNR levels required for 50% correct repetition of the last word in low-context sentences was highest when there was no spatial separation vs. when there was a separation between the target sentences and the babble background, and were on average lower for real than for virtual locations
Summary
Conversations with friends, co-workers, healthcare providers, and others often occur in noisy environments (e.g., malls, restaurants, stores, offices) in which there are a number of different sound sources that could interfere with one’s ability to communicate effectively. The presence of other talkers, who are not part of the conversation, can be distracting when one is trying to follow a conversation between two or more people Such multi-talker auditory scenes increase the complexity of both the perceptual and cognitive processes required for comprehension. To effectively follow a multi-talker conversation, the listener needs to perceptually segregate the talkers from one another, efficiently switch attention from one talker to another, keep track of what was said by whom, extract the meaning of each utterance, store this information in memory for future use, integrate incoming information with what each conversational participant has said or done in the past, and draw on the listener’s own knowledge of the conversation’s topic to extract general themes and ideas (Murphy et al, 2006; Schneider et al, 2010). It is not surprising that people in general find such situations stressful, and that older individuals, whose auditory and cognitive systems may be in decline, and even young, healthy listeners who are operating in their second or third language, find such situations devastating
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