Integrating expectations and outcomes: Preschoolers’ developing ability to reason about others’ emotions

People's emotional experiences depend not only on what actually happened, but also on what they thought would happen. Inferring others' expectations and how these expectations influence others' emotions is an important aspect of human social intelligence, allowing us to understand how others feel even when outcomes are uninformative and expectations are not explicitly communicated. Prior work suggests an abstract understanding of how expectations modulate emotional responses may not emerge until 7 to 8 years of age. Using a novel paradigm that capitalizes on intuitive physics to generate contextually plausible expectations, we sought to find earlier evidence for expectation-based emotion inference. Given two bowlers who experienced identical outcomes (hitting 3 out of 6 pins), we varied the physical trajectory of their balls such that one would initially expect to hit all pins (High-Expectation), while the other would expect to hit nothing (Low-Expectation). In Experiment 1, while both 4- and 5-year-olds appropriately adjusted the characters' happiness ratings upward (Low-Expectation) or downward (High-Expectation) with respect to their initial emotions, only 5-year-olds made adjustments robust enough to manifest as higher happiness ratings for the Low-Expectation than High-Expectation character. We replicate these results in Experiments 2-3 and show that 5-year-olds reliably differentiate the characters' emotions even when explicit information about their expectations is unavailable and must be inferred from the physical context (i.e., ball trajectories). Together, these results provide the earliest evidence for expectation-based emotion reasoning and suggest that the ability to spontaneously generate and consider others' expectations continues to develop during preschool years.