In a sample of 141 preschoolers, ages 4 to 6, we find children display overconfidence in cognitive and motor skill tasks, a result that replicates that of adults. Both set of findings suggest the bias may not be learned behavior. Moreover, we find right-handed children to display more overconfidence in the cognitive task, whereas low digit-ratio children show more overconfidence in fine and gross motor skill tasks. Handedness polymorphism has been linked to neurological differences, and in literature low digit ratios are commonly associated with high fetal testosterone.