Pupillometry reveals communication-induced object expectations in 12- but not 8-month-old infants

Several interaction-based and looking-time studies suggest that 1-year-old infants understand the referential nature of deictic gestures. However, these studies have not unequivocally established that referential gestures induce object expectations in infants prior to encountering a referent object, and have thus remained amenable to simpler attentional highlighting interpretations. The current study tested whether nonlinguistic referential communication induces object expectations in infants by using a novel pupil dilation paradigm. In Experiment 1, 12-month-olds watched videos of a protagonist who either pointed communicatively toward an occluder in front of her or remained still. At test, the occluder opened to reveal one of two outcomes: an empty surface or a toy. Results showed that infants' pupils were larger for the unexpected outcome of an empty surface following a point compared to the control condition (an empty surface following no point). These differences were not caused by differences in looking times or directions. In Experiment 2, an attention-directing nonsocial control cue replaced the referential communication. The cue did direct 12-month-olds' attention to the occluder, but it did not induce an object expectation. In Experiment 3, we tested 8-month-olds in the setting of Experiment 1. In contrast to 12-month-olds, 8-month-olds did not reveal object expectations following communication. Findings demonstrate that communicative pointing acts induce object expectations at 12 months of age, but not at 8 months of age, and that these expectations are specific to a referential-communicative as opposed to an attention-directing nonsocial cue.