Stable individual differences in infants’ responses to violations of intuitive physics

https://www.pnas.org/content/118/27/e2103805118

Infants look longer at impossible or unlikely events than at possible events. While these responses to expectancy violations have been critical for understanding early cognition, interpreting them is challenging because infants’ responses are highly variable. This variability has been treated as an unavoidable nuisance inherent to infant research.

Here we asked whether the variability contains signal in addition to noise: namely, whether some infants show consistently stronger responses to expectancy violations than others. Infants watched two unrelated physical events 6 mo apart; these events culminated in either an impossible or an expected outcome.

We found that infants who exhibited the strongest looking response to an impossible event at 11 mo also exhibited the strongest response to an entirely different impossible event at 17 mo. Furthermore, violation-of-expectation responses in infancy predicted children’s explanation-based curiosity at 3 y old.

In contrast, there was no longitudinal relation between infants’ responses to events with expected outcomes at 11 and 17 mo, nor any link with later curiosity; hence, infants’ responses do not merely reflect individual differences in attention but are specific to expectancy violations. Some children are better than others at detecting prediction errors—a trait that may be linked to later cognitive abilities.

Finally, as an exploratory investigation, at 37 mo we collected parental reports of children’s explanation-based curiosity and interest in novelty [using the Interest and Deprivation Young Children Curiosity Scales (11)], and expressive vocabulary [using the Developmental Vocabulary Assessment for Parents (12)] (experiment 3, n = 50) (these were collected via parental report because the COVID-19 pandemic precluded in-person testing). An example item from the explanation-based curiosity measure was, “My child devotes considerable effort trying to figure out things that are confusing or unclear.” An example from the novelty seeking measure was, “My child is attracted to new things in his/her environment” (SI Appendix).

First, our findings raise the question of whether individual differences in infants’ responses to expectancy violations impact later development. Children’s learning is enhanced immediately following an expectancy violation (5). Combined with the results of our longitudinal study, this points to the possibility that some children not only respond more to violations but also learn better from them.

Stahl & Feigenson (2015) Observing the unexpected enhances infants’ learning and exploration. Science 348, 91–94.