| Summary: | The purpose of the present study was to investigate how adverse listening conditions
affect the ability of normal-hearing listeners to identify the boundaries between discourse
topics, or when "what is being talked about" has changed. Twelve subjects (21 to 35 years)
listened to digitized recordings of a single speaker's monologues presented in three
background noise conditions (+5, 0 and -5 dB S:N). Subjects were asked to push a button
when they thought that a change of topic was about to occur in the monologue. Subject
responses were analyzed for the latency of topic boundary identification and the number and
location of responses. The role of prosodic cues in the identification of topic boundaries was
also evaluated. It was found that as the listening condition became less favourable, listeners
were slower to identify topic boundaries, were less certain as to where topic boundaries
occurred, and relied more heavily on cues to topic initiation than on cues to topic
termination for identification of topic boundaries. It was also shown that as the signal-tonoise
ratio decreased, listeners were less able to utilize cues to topic boundary that are
present in low amplitude utterances such as pitch range and contour, laryngealization and
pre-boundary syllable lengthening, but that listeners relied on the prosodic cue of pause
duration to identify topic boundaries equally in all three listening conditions.
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