How toddlers make decisions under uncertainty

On the road to introspection, toddlers seek evidence when they are confronted with epistemic uncertainty

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If you give a 2-year-old a new, complicated toy, she may look puzzled at first and perhaps turn to a caregiver for help. Yet once she figures out how the toy works, she is likely to launch right into playing with it. Anyone who has ever interacted with toddlers has observed them giving quizzical looks that suggest uncertainty, or giving satisfied grins that suggest confidence. Before becoming a mom, I rarely interacted with young children because my research focused on cognitive development during the school years.  

But when my aunt caught my son on camera (picture below) responding with gestures to the question: “Where is mommy?” I started paying attention. I started wondering about the meaning of these expressions. Was he aware that he did not know where I was, or had he simply learned to respond this way to any situation that did not quite go his way (e.g., mommy is not around, toy is hard to play with)? Did he actually experience uncertainty?

Photo by Serena Turci

In my work with school-aged children, I often ask them how sure or unsure they feel about each of their answers in our laboratory tasks. Clearly this is not possible with very young children. So, together with my PhD student, Sarah Leckey, and other coauthors, I started thinking about alternatives. Our goal was to figure out whether situations that elicit experiences of uncertainty in older children and adults would cause toddlers to pause and seek out additional information. If so, common mechanisms may underlie both toddlers’ behavioral responses and older children subjective experiences. 

To test these ideas, we had 2-year-olds make easy and difficult perceptual decisions. They had to identify a target, such as an animal, from two partially occluded pictures that were either similar (making it harder to find the correct one) or dissimilar (making it easier to do so). Two-year-olds were less accurate in similar trials. We modeled their response times with drift diffusion models and found that toddlers accumulated evidence more slowly during similar trials. We also analyzed their eye movements and found that toddlers took longer to settle the gaze on the selected image on inaccurate responses, and switched their gaze between response options more frequently on inaccurate and similar trials. And, an analysis of our video recordings of the experimental sessions showed that the most difficult trials were also the ones in which toddlers were most likely to turn to the experimenter for help and state “I don’t know.”

Overall, the toddlers in our study responded cautiously to uncertain situations by slowing down and collecting disambiguating information. These behaviors seem integral to the experience of uncertainty, and suggest that even toddlers may begin to experience uncertainty in the same way and for the same reasons as older children and adults.  Our hypothesis is that as young children continue to face situations requiring decisions with uncertain outcomes, they will learn to recognize the most informative cues to uncertainty, and learn to map those cues to subjective feelings to verbal labels to describe them.  Our next step will be to assess young children over time to see whether their early behavioral responses indeed reflect an emerging awareness of uncertainty and promote a capacity for introspection.

Leckey, S., Selmeczy, D., Kazemi, A. et al. Response latencies and eye gaze provide insight on how toddlers gather evidence under uncertainty. Nat Hum Behav (2020).

Simona Ghetti

Professor, University of California, Davis