A value-driven McGurk effect: Value-associated faces enhance the influence of visual information on audiovisual speech perception and its eye movement pattern.

This study investigates whether and how value-associated faces affect audiovisual speech perception and its eye movement pattern. Participants were asked to learn to associate particular faces with or without monetary reward in the training phase, and, in the subsequent test phase, to identify syllables that the talkers had said in video clips in which the talkers' faces had or had not been associated with reward. The syllables were either congruent or incongruent with the talkers' mouth movements. Crucially, in some cases, the incongruent syllables could elicit the McGurk effect. Results showed that the McGurk effect occurred more often for reward-associated faces than for non-reward-associated faces. Moreover, the signal detection analysis revealed that participants had lower criterion and higher discriminability for reward-associated faces than for non-reward-associated faces. Surprisingly, eye movement data showed that participants spent more time looking at and fixated more often on the extraoral (nose/cheek) area for reward-associated faces than for non-reward-associated faces, while the opposite pattern was observed on the oral (mouth) area. The correlation analysis demonstrated that, over participants, the more they looked at the extraoral area in the training phase because of reward, the larger the increase of McGurk proportion (and the less they looked at the oral area) in the test phase. These findings not only demonstrate that value-associated faces enhance the influence of visual information on audiovisual speech perception but also highlight the importance of the extraoral facial area in the value-driven McGurk effect.