Pupillometric VoE paradigm reveals that 18- but not 10-month-olds spontaneously represent occluded objects (but not empty sets)

Altercentric Memory Error at 9 Months But Correct Object Memory by 18 Months Revealed in Infants' Pupil

It was recently proposed that infants have a memory bias for events witnessed together with others. This may allow infants to prioritize relevant information and to predict others' actions, despite limited processing capacities. However, when events occur in the absence of others, for example, an object changes location, this would create altercentric memory errors where infants misremember the object's location where others last saw it. Pupillometry presents a powerful tool to examine the temporal dynamics of such memory biases as they unfold. Here, we showed infants aged 9 (N = 97) and 18 months (N = 79) videos of an agent watching an object move to one of two hiding locations. The object then moved from location A to B, which the agent either missed (leading to her false belief) or witnessed (true belief). The object subsequently reappeared either at its actual or, surprisingly, its initial location. As predicted by the altercentric theory, 9-month-old infants expected the object where the agent falsely believed it to be and not where it really was, as indicated in their pupil dilation. In contrast, 18-month-old infants seemed to remember the object's actual location. Infants' memory errors did not predict correct action anticipation when the agent reached into one of the locations to retrieve the object. This indicates that infants show altercentric memory errors at a young age, which vanish in the second year of life. We suggest that this bias helps young infants to learn from others, but recedes as they become more capable of acting on the world themselves.

Out of sight, not out of mind: New pupillometric evidence on object permanence in a sample of 10- and 12-month-old German infants

Findings on the emergence and interpretation of early object representation in the first year of life diverge widely between designs that employ looking times versus action-based measures. As a promising new approach, pupillometry has produced evidence for object permanence at 18 months of age, but not younger as of yet. In the current study, we (re)investigated object permanence following occlusion events in a pupillometric violation-of-expectation paradigm optimized for younger infants. During each trial, infants observed a toy object's occlusion and prompt reveal in the expected condition or its absence in the unexpected condition. Across two experiments, we show that 10- and 12-month-old infants' (total N = 82) pupils dilate in response to unexpected object disappearances relative to expected appearances. Control analyses revealed no differences between the scenes before the experimental manipulation, excluding perceptual interpretations. We further report an age-dependent effect of condition on pupil responses, with unexpected outcomes triggering greater pupil dilation in the older group. These results provide positive pupillometric evidence in support of object permanence in the context of a violation-of-expectation paradigm at 10 and 12 months of age.

The pupil collaboration: A multi-lab, multi-method analysis of goal attribution in infants

The rise of pupillometry in infant research over the last decade is associated with a variety of methods for data preprocessing and analysis. Although pupil diameter is increasingly recognized as an alternative measure of the popular cumulative looking time approach used in many studies (Jackson & Sirois, 2022), an open question is whether the many approaches used to analyse this variable converge. To this end, we proposed a crowdsourced approach to pupillometry analysis. A dataset from 30 9-month-old infants (15 girls; Mage = 282.9 days, SD = 8.10) was provided to 7 distinct teams for analysis. The data were obtained from infants watching video sequences showing a hand, initially resting between two toys, grabbing one of them (after Woodward, 1998). After habituation, infants were shown (in random order) a sequence of four test events that varied target position and target toy. Results show that looking times reflect primarily the familiar path of the hand, regardless of target toy. Gaze data similarly show this familiarity effect of path. The pupil dilation analyses show that features of pupil baseline measures (duration and temporal location) as well as data retention variation (trial and/or participant) due to different inclusion criteria from the various analysis methods are linked to divergences in findings. Two of the seven teams found no significant findings, whereas the remaining five teams differ in the pattern of findings for main and interaction effects. The discussion proposes guidelines for best practice in the analysis of pupillometry data.

The pupillometry of the possible: an investigation of infants' representation of alternative possibilities

Contrasting possibilities has a fundamental adaptive value for prediction and learning. Developmental research, however, has yielded controversial findings. Some data suggest that preschoolers might have trouble in planning actions that take into account mutually exclusive possibilities, while other studies revealed an early understanding of alternative future outcomes based on infants' looking behaviour. To better understand the origin of such abilities, here we use pupil dilation as a potential indicator of infants' representation of possibilities. Ten- and 14-month-olds were engaged in an object-identification task by watching video animations where three different objects with identical top parts moved behind two screens. Importantly, a target object emerged from one of the screens but remained in partial occlusion, revealing only its top part, which was compatible with a varying number of possible identities. Just as adults' pupil diameter grows monotonically with the amount of information held in memory, we expected that infants' pupil size would increase with the number of alternatives sustained in memory as candidate identities for the partially occluded object. We found that pupil diameter increased with the object's potential identities in 14- but not in 10-month-olds. We discuss the implications of these results for the foundation of humans' capacities to represent alternatives. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.