Goulding, Brandon2021-09-072021-09-072021-09-072021-08-04http://hdl.handle.net/10012/17352Deciding what is possible is an essential human ability, and our judgments about possibility often appear effortless and straightforward. But how do we actually decide whether something is possible or impossible? This dissertation explores two strategies that children might use to infer the possibility of strange or improbable events. The first posits that children think about the causal circumstances that could enable an event when judging whether it could happen. The second instead suggests that children’s inferences about possibility are guided by a memory-based heuristic that compares potential events to known events. Children’s (N = 1,068) use of these strategies are explored across three papers. Chapter 2 investigated 4- to 7-year-old’s beliefs about the possibility of improbable events and impossible events in dreams and stories, finding that children judged more events to be possible in these fantastical worlds than in real life. However, across all worlds children more often judged improbable events possible than impossible events, and children only affirmed impossible events if the events were especially dream- or story-like. The findings suggest that children’s beliefs about fantastical worlds are partly constrained by their real-world intuitions, and partly driven by what they know to have occurred in each kind of world. Chapter 3 explored whether 4- to 6-year-old children use a memory-based similarity heuristic to infer possibility, in which events are judged possible if they are similar to a known event. The findings provide evidence for a similarity heuristic in 5- and 6-year-olds possibility judgments: children judged similar improbable events possible, but did not affirm dissimilar improbable events or similar impossible events. Finally, Chapter 4 examined whether providing 4- to 7-year-old children with information about enabling causal circumstances would lead them to affirm the possibility of improbable events. It also contrasted the effect of this kind of causal information with information about similar events. The findings show that causal information alone did little to alter children’s beliefs about possibility. However, the findings again show evidence for a similarity heuristic in 5- and 6-year-olds possibility judgments, as children more often affirmed improbable events if they were first told about a similar event. Further, this study provides tentative evidence that a combination of enabling causal knowledge and information about a similar event has the greatest positive impact on children’s possibility judgments for improbable events. Together, this work suggests that our beliefs about possibility are largely driven by our familiarity with, and memory of, past events.endevelopmental psychologyconceptual developmentcognitive developmentpossibilityextraordinary eventsheuristicsDoctoral Thesis