Eye blinks are perceived as communicative signals in human face-to-face interaction.

Paul Hömke,Judith Holler,Stephen C Levinson,Nicholas D Duran

doi:10.1371/journal.pone.0208030

Paul Hömke, Judith Holler + Show 2 more

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https://doi.org/10.1371/journal.pone.0208030

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Abstract

In face-to-face communication, recurring intervals of mutual gaze allow listeners to provide speakers with visual feedback (e.g. nodding). Here, we investigate the potential feedback function of one of the subtlest of human movements—eye blinking. While blinking tends to be subliminal, the significance of mutual gaze in human interaction raises the question whether the interruption of mutual gaze through blinking may also be communicative. To answer this question, we developed a novel, virtual reality-based experimental paradigm, which enabled us to selectively manipulate blinking in a virtual listener, creating small differences in blink duration resulting in ‘short’ (208 ms) and ‘long’ (607 ms) blinks. We found that speakers unconsciously took into account the subtle differences in listeners’ blink duration, producing substantially shorter answers in response to long listener blinks. Our findings suggest that, in addition to physiological, perceptual and cognitive functions, listener blinks are also perceived as communicative signals, directly influencing speakers’ communicative behavior in face-to-face communication. More generally, these findings may be interpreted as shedding new light on the evolutionary origins of mental-state signaling, which is a crucial ingredient for achieving mutual understanding in everyday social interaction.

Highlights

Human communication is a joint activity [1]
‘no feedback’ control condition were statistically indistinguishable (β = 0.87, SE = 1.41, t = 0.618, p = .537). These results show that speakers were sensitive to the absence of visual feedback, and to subtle differences in blink duration
Are speakers sensitive to listener blink duration in face-to-face communication? Our results reveal that subtle, millisecond differences in blink duration caused speakers to design answers to questions that differed substantially in length, namely by several seconds

Summary

Introduction

Human communication is a joint activity [1]. Rather than just one party being active at a time by producing speech, both speaker and listener contribute signals critical to progressing the exchange of information. Listener feedback (or ‘back-channel’ responses [2]), such as ‘mhm’ or ‘uhu’, are crucial for successful communication since they facilitate the process of grounding [3] and the achievement of mutual understanding. Eliminating or reducing listener feedback is detrimental to speakers’ behavior [4]. Humans tend to engage in mutual gaze when communicating without necessarily signaling aggressive intent or affiliative interest [5,6]. For successful face-to-face communication, these recurring intervals of mutual gaze are important, as they allow listeners to provide speakers with visual feedback, such as nodding.

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