The effects of directing, switching, and misdirecting auditory spatial attention in a complex listening situation were investigated in 8 younger and 8 older listeners with normal-hearing sensitivity below 4 kHz.
In two companion experiments, a target sentence was presented from one spatial location and two competing sentences were presented simultaneously, one from each of two different locations. Pretrial, listeners were informed of the call-sign cue that identified which of the three sentences was the target and of the probability of the target sentence being presented from each of the three possible locations. Four different probability conditions varied in the likelihood of the target being presented at the left, center, and right locations. In Experiment 1, four timing conditions were tested: the original (unedited) sentences (which contained about 300 msec of filler speech between the call-sign cue and the onset of the target words), or modified (edited) sentences with silent pauses of 0, 150, or 300 msec replacing the filler speech. In Experiment 2, when the cued sentence was presented from an unlikely (side) listening location, for half of the trials the listener’s task was to report target words from the cued sentence (cue condition); for the remaining trials, the listener’s task was to report target words from the sentence presented from the opposite, unlikely (side) listening location (anticue condition).
In Experiment 1, for targets presented from the likely (center) location, word identification was better for the unedited than for modified sentences. For targets presented from unlikely (side) locations, word identification was better when there was more time between the call-sign cue and target words. All listeners benefited similarly from the availability of more compared with less time and the presentation of continuous compared with interrupted speech. In Experiment 2, the key finding was that age-related performance deficits were observed in conditions requiring anticue but not cue responses.
The findings from Experiment 1 suggest that for both age groups, stream continuity mediates the process of allocating and maintaining auditory spatial attention when the target originates at an expected location, but that time is needed for the reallocation of auditory spatial attention when the target originates at an unexpected location. The findings from Experiment 2 suggest that when attention is momentarily misdirected, difficulties disengaging attention may help explain why older adults with good hearing report difficulty communicating in multi-talker listening situations.