The ability to monitor epistemic uncertainty is critical for self-directed learning. However, we still know little about youngchildren’s ability to detect uncertainty in their mental repre-sentations. Here we asked whether a spontaneous informationgathering behavior – social referencing – is driven by uncer-tainty during early childhood. Children ages 2-5 completed aword-learning task in which they were presented with one ortwo objects, heard a label, and were asked to put the labeledobject in a bucket. Referential ambiguity was manipulatedthrough the number of objects present and their familiarity. InExperiment 1, when there were two novel objects and a novellabel, the referent was ambiguous; when there were two famil-iar objects, or only one novel or familiar object, the referentwas known or could be inferred. In Experiment 2, there wereeither two novel objects, two familiar objects, or one familiarand one novel object; in the latter case the referent could be in-ferred by excluding the familiar object. To further manipulatethe availability of referential cues, the experimenter gazed ateither the target or the center of the table while labeling the ob-ject. In both experiments, children looked at the experimentermore often while making their response when the referent wasambiguous. In Experiment 2, children also looked at the ex-perimenter more when there was one familiar and one novelobject, but only when the experimenter’s gaze during label-ing was uninformative. These results suggest that children’ssocial referencing is a sensitive index of graded epistemic un-certainty.
