
The ubiquity yet brevity of eye contact in natural conversation, averaging 1.9 s ( 9), also suggests that these attentional nudges are not scattered randomly but occur at precise times to optimize the attention of both parties. It is possible that the known effects of eye contact on arousal ( 10 – 12) and attention ( 13 – 15) may nudge partners at critical moments in the conversation that facilitate this exchange. Eye contact-when two people look at each other’s eyes-occurs ubiquitously in conversation, often at the ends of turns when partners pass the conversational baton ( 6 – 9). There are several reasons to believe that eye contact may play an instrumental role. Engaging conversation must continuously negotiate the delicate balance between creating shared understanding while allowing the conversation to move forward and evolve. Even deciding when conversation should end is a feat of social coordination ( 5). When there is insufficient common ground, people talk past each other. Given too few independent insights, conversation stagnates. Conversation partners must weave shared understanding from alternating independent contributions ( 1 – 4) in an act of spontaneous, dynamic cocreation. This effortlessness obscures the complexities involved. Good conversations proceed effortlessly, as if conversation partners share a single mind. Furthermore, we speculate that eye contact may play a corrective role in disrupting shared attention (reducing synchrony) as needed to facilitate independent contributions to conversation. This relationship suggests that eye contact signals when shared attention is high. However, rather than elicit synchrony, eye contact commences as synchrony peaks and predicts its immediate and subsequent decline until eye contact breaks. We find that eye contact is positively correlated with synchrony as well as ratings of engagement by conversation partners. Here we test whether eye contact, a common feature of conversation, predicts this coordination by measuring dyadic pupillary synchrony (a corollary of shared attention) during natural conversation. How two minds achieve this coordination is poorly understood. Every conversation weaves a unique shared narrative from the contributions of independent minds, requiring partners to flexibly move into and out of alignment as needed for conversation to both cohere and evolve. Its frequency and ease belie its complexity. Conversation is the platform where minds meet: the venue where information is shared, ideas cocreated, cultural norms shaped, and social bonds forged.
