No clear evidence for a domain-general violation of expectation effect in the pupillary responses of 9- to 10-month-olds

Violation of expectation (VOE) paradigms are key to understanding infants' early knowledge. In VOE paradigms, infants are presented sequences of events either according with or violating regularities of their physical or social environment. Infants' violated expectations may result in a surprise response, such as longer looking times or specific neural correlates. There is an increasing interest in utilizing infants' pupil dilation as an index of their surprise. However, to date, no study has systematically examined infants' pupillary response across different VOE paradigms. In this preregistered study, we measured 9- to 10-month-olds' pupil dilation (N = 21) in response to a common VOE paradigm across four knowledge domains (action, cohesion, number, solidity). In a pre-registered analysis, infants' pupillary response did not differ between expected and unexpected outcomes in any of these domains. We compared the effect of different analyses parameter choices in a specification curve analysis which revealed that very few choices would have led to significant results. The results demonstrate that across analytical decisions regarding data preprocessing and analysis we do not find evidence for the hypothesized effect. A subsequent permutation test revealed that our original data slightly diverges from randomly shuffled data. We can therefore not unambiguously reject the null hypothesis. We discuss these findings theoretically and methodologically and highlight the need for combining multiple measures to better understand the methods we apply to examine infants' knowledge about their environment.