Task demands affect lipreaders’ search for information

Two experiments were conducted to determine whether a lipreader’s task (making phonemic or prosodic distinctions about the spoken message) changes the regions of the talker’s face from which information is needed, and whether lipreaders are sensitive to these changes. An initial experiment found that when face movement was limited to the talker’s lips‐plus‐mandible region, the accuracy of intonation judgments was reduced but the accuracy of phonemic judgments was not. A second experiment then recorded gaze direction of lipreaders as they attempted to make judgments about the phonemic, stress, or intonation contour characteristics of short utterances. Results indicated that they spent more time looking at upper portions of the face when judging intonation contours than in the other conditions. Other differences in the eye movement patterns were also found among task conditions. Thus lipreaders are aware that different aspects of the speech information are signaled at different facial regions, and can adjust their direction of gaze to take advantage of this knowledge.