Background/ the question: Imagining and contrasting possibilities is central to many human activities, in the arts and sciences, as well as in everyday life. For example, when ordering dinner we often contrast alternative options (ordering ceviche or a steak?), we consider alternative hypothesis (is raw fish or grilled meat the main dish of the restaurant?), and predict possible scenarios (if the raw fish were the flagship dish of the kitchen, many people would be having ceviche.) Thus, the ability to consider multiple possibilities is a fundamental support when we prepare for future events and try to make the most adaptive choices. Yet, despite its importance for human cognition, we don’t know what the origin of this capacity is. Contemporary cognitive scientists are vividly debating whether language and experience are necessary to imagine possibilities, or else thinking of possibilities is a basic human ability and thus emerges early. One way to answer this question is to explore whether infants are able to go beyond the here and now and imagine future possibilities.
One reason of skepticism regarding infants and young children understanding of possibilities is that they often make striking mistakes when facing uncertainty. For example, if you tell a four-years-old-child that she has to catch a ball that you are going to drop in a forking tube with two exits (i.e., the ball will roll down either on the right or on the left arm of the tube), she will prepare for all possible outcomes, covering both exits with her hands. However, the 2-year-olds often cover only one exit (Redshaw and Suddendorf, 2016), diminishing their chance to catch the ball. This failure was often explained by the lack of modal concepts that would enable them to imagine and prepare for alternative future possibilities at this age.
However, there can be alternative interpretations of young children’s failure. Perhaps, they DO have an intuitive understanding of possibilities, but they are not very good strategists and they make mistakes when they have to generate action plans considering all possible outcomes. To test the hypothesis that infants may already possess a basic understanding of possibilities, we devised a new method to measure this ability without asking to plan actions or make decisions: the pupillometry of the possible. Previous studies with adults have shown that the pupil has the surprising property to dilate when we make a mental effort (e.g., try to remember an increasing number of things or make complex mental calculations). We asked whether this would be also the case when infants can represent multiple possibilities. Recording infants’ pupil diameter, thus, allowed us to test whether the pupil size increases in function of the number of possibilities they could encode.
We presented 14-month-olds infants with movies depicting physical events where there was uncertainty about the identity of an object that was in partial occlusion. All objects we used shared some visual features: e.g. the upper parts of a toy elephant, a doll and a ball looked the same. Then, these objects participated in a series of occlusion events. We contrasted the pupil dilation elicited by scenes where the identity of the partially occluded object could be known (e.g. the toy elephant) with scenes, where the visible fragment (the top of the object) was insufficient for reidentification, so infants could only think about possibilities: e.g. is this the doll or it is the ball?. We found that infants’ pupil dilated more when they were observing a hidden object with multiple possible identities, than when the object had only one possible identity. This is what one should expect if the babies are imagining the possible identities of the object.
The scientific key points: a new paper to be published in the Philosophical Transactions of the Royal Society B in the dedicated theme issue Thinking about possibilities: mechanisms, ontogeny, functions, and phylogeny on 10/31/2022 finds that babies as young at 14 months spontaneously think about multiple possibilities when presented with an “ambiguous” object appearance. By recording the diameter of the infants’ pupil, we could measure the mental effort produced by the generation of the alternative hypotheses. This reveals that the foundation of our capacity to imagine and reason about alternative possibilities is already present very early on, in infants that cannot yet speak.
The study: In a series of experiments performed at the Cognitive Development Center of the Central European University, Nicolò Cesana-Arlotti (Johns Hopkins University) together with Bálint Varga (Central European University) and Ernő Téglás (Central European University) asked whether 14- and 10-month-olds infants can represent alternative possibilities when facing uncertain events, by using their 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 (a doll, a toy elephant and a ball) 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, one in one condition (i.e., the elephant), two in the other (i.e., the doll or the ball). 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. This result indicates that infants spontaneously react to ambiguous events with the representation of alternative possibilities.
Why this matter: We learn, predict, and decide by conceiving small arrays of possibilities that cannot jointly happen but one of which we assume must occur. The developmental foundations of our intuitive sense of the relevant possibilities are, however, unknown. Our pupillometric tests indicate that one milestone of such cognitive resources, the capacity to represent multiple mutually incompatible possibilities, is in place in humans at least from the second year of life.
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Cite the article: Cesana-Arlotti N, Varga B, Téglás E. 2022 The pupillometry of the possible: an investigation of infants’ representation of alternative possibilities. Phil. Trans. R. Soc. B 377: 20210343. https://doi.org/10.1098/rstb.2021.0343
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Contact:
Nicoló Cesana-Arlotti: nicolocesanaarlotti@gmail.com
Varga Bálint: Varga_Balint02@phd.ceu.edu
Téglás Ernő: teglase@ceu.edu