“Yay! Yuck!” Toddlers use incongruent emotions to reason about hidden objects
Infants show impressive sensitivity to others’ emotions from early on, attending to and discriminating different facial emotions, using emotions to decide what to approach or avoid, and recognizing that certain objects and events are likely to produce certain emotional responses. But do infants and toddlers also recognize more abstract features of emotions—features that are not tied to any one emotion in particular? Here we examined the development of the higher order expectation that emotions are more or less mutually exclusive, asking whether young children recognize that people generally do not express two conflicting emotions towards a single stimulus. We first asked whether 26-month old toddlers can use an agent’s incongruent versus congruent emotional responses (“Yay! Yuck!” versus “Yay! Wow!”) to reason about how many objects were hidden in a box. We found that toddlers inferred that incongruent emotions signaled the presence of two numerically distinct objects (Experiment 1). This inference relied on the incongruent emotions being produced by a single agent; when two different agents gave two incongruent emotional responses, toddlers did not assume that two objects must be present (Experiment 2). Finally, we examined the developmental trajectory of this ability. We found that younger, 20-month olds failed to use incongruent emotions to individuate objects (Experiment 3), although they readily used incongruent novel labels to do so (Experiment 4). Our results suggest that by 2-years of age, children use higher order knowledge of emotions to make inferences about the world around them, and that this ability undergoes early development.