Project Summary/Abstract Optimism – a cognitive bias to overestimate positive future outcomes – may play a critical function in the early years of life, driving how children learn, confront challenges, and persevere in the face of setbacks. Roughly 80% of adults make optimistically biased predictions, and although optimism is adaptive and provides motivational, social, and health benefits, virtually no empirical research has tested how optimism develops. Further, the lack of an optimism bias – either presented as realism or pessimism – is associated with depression in adolescents and adults, and may be driven by early life experiences. My objective is to develop an integrated and systematic framework for the development of optimism in preschool-aged children, focusing on the role of early experience (positive and negative) on these processes, and specifying connections between early optimism and depressive symptoms/negative affect states. Estimates are that 1-2% of preschoolers exhibit symptoms that meet the diagnostic criteria for Major Depressive Disorder, whereas 9-12% exhibit sub-clinical symptoms. Further, these prevalence rates are likely higher in children from disadvantaged backgrounds, and when considering negative affect more widely. My predictions are that optimism is present early in a broad capacity and influences how children learn from and about the world. As they experience event outcomes, and probabilistic reasoning improves, the magnitude of their optimistic predictions diminishes. Further, divergent developmental trajectories may emerge such that optimism declines more steeply in children who experience more negative life events, compounding the disadvantages they face. Lack of early optimism may also be a key symptom of depression in preschoolers and/or perpetuate symptoms over development. Recent data from our lab indicate that at least a subset of preschoolers do have an optimism bias – they make optimistic predictions for events that concern themselves but not others – providing initial support for these predictions. The proposed studies will test 3- to 5-year-olds from racially and socioeconomically diverse backgrounds to determine how early optimism is expressed and maintained, socioeconomic and family factors affecting optimism, and how optimism guides learning in typically developing children and those with elevated depressive symptoms. I introduce new experimental methods to test optimism, learning, and probabilistic reasoning in preschoolers, coupled with extensive parent reports on family background, children's experiences, motivational approach, parenting style, and an established measure of child depression. Experimentally, I will test if children offer optimistic, accurate, or pessimistic predictions for event outcomes, assess domain and state-related variability in optimism, and determine if children incorporate new positive, but not negative, information into their beliefs about how likely an event is to occur (...