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

Abstract

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’.

Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny

“…There are at least four plausible explanations for these conflicting findings. First, in line with Cesana-Arlotti et al's [47] interpretation of the infant data, non-human animals may possess the conceptual apparatus necessary to solve both types of tasks yet fail the physical uncertainty tasks because of difficulties with action planning and decision-making [105]. Second, animals may be able to reason over mutually exclusive possibilities in situations of epistemic but not physical uncertainty [106]-opposite to the pattern observed in young children [67].…”

“…In recent years, multiple lines of research have begun to map the early origins of representing and reasoning about possibilities (and probabilities) in humans, often using behavioural and physiological measures that enable the testing of nonverbal infants [46]. In this issue, Cesana-Arlotti et al [47] build on their previous work [11,12] and present novel pupillometric evidence that even 14-month-old infants can simultaneously represent two mutually exclusive possibilities, which contrasts with previous studies showing that children younger than 4 years struggle to prepare for such possibilities (e.g. [17]).…”

“…B 377: 20210333 thinking in behaviour, at least, undergoes a protracted development in humans. A key question for future research will be to uncover whether this gradual development merely reflects improvements in action planning and decision-making, as Cesana-Arlotti et al [47] would have it, or whether it reflects genuine conceptual transformation, as Harris [48] and Grigoroglou & Ganea [57] would have it.…”

The re-emergence of the language of thought hypothesis: consequences for the development of the logic of thought

“…Thus, we may expect that if infants have no logical operators, they will simulate and store just one disjunct at the time (for a similar prediction, see (Leahy & Carey, 2020)). A new study provides evidence that infants do NOT respond to objects with multiple possible identities by simulating just a single identity at the time (Cesana-Arlotti et al, 2022), as their pupil diameterindexing processing loadincreases with the number of possible identities. While infants might have simulated multiple models, the proposal of a single complex logical representation (e.g., "the elephant OR the ball") may best account for this result, considering their limited cognitive resources.…”

“…(C) Infants watched visually identical events where a half-hidden object was compatible with a varying number of identities (one or two). Infants' pupil dilation (an index of processing load) was higher when there were two alternatives compatible with the object, suggesting that infants were not simulating just a single identity regardless of the alternative possibilities (adapted from (Cesana-Arlotti et al, 2022)).…”