Perceptual and conceptual novelty independently guide infant looking behaviour: a systematic review and meta-analysis

Human infants are born with their eyes open and an otherwise limited motor repertoire; thus, studies measuring infant looking are commonly used to investigate the developmental origins of perception and cognition. However, scholars have long expressed concerns about the reliability and interpretation of looking behaviours. We evaluated these concerns using a pre-registered ( https://osf.io/jghc3 ), systematic meta-analysis of 76 published and unpublished studies of infants' early physical and psychological reasoning (total n = 1,899; 3- to 12-month-old infants; database search and call for unpublished studies conducted July to August 2022). We studied two effects in the same datasets: looking towards expected versus unexpected events (violation of expectation (VOE)) and looking towards visually familiar versus visually novel events (perceptual novelty (PN)). Most studies implemented methods to minimize the risk of bias (for example, ensuring that experimenters were naive to the conditions and reporting inter-rater reliability). There was mixed evidence about publication bias for the VOE effect. Most centrally to our research aims, we found that these two effects varied systematically-with roughly equal effect sizes (VOE, standardized mean difference 0.290 and 95% confidence interval (0.208, 0.372); PN, standardized mean difference 0.239 and 95% confidence interval (0.109, 0.369))-but independently, based on different predictors. Age predicted infants' looking responses to unexpected events, but not visually novel events. Habituation predicted infants' looking responses to visually novel events, but not unexpected events. From these findings, we suggest that conceptual and perceptual novelty independently influence infants' looking behaviour.