The Development of Modal intuitions: A Test of Two Accounts

• In Event: How Children Judge the Possibility of Improbable and Impossible Events

Abstract

Pet peacocks and polka-dotted planes may not be things that a person encounters every day; indeed, an individual may never encounter these things. Yet even without first-hand evidence, adults report that unusual entities and phenomena like these are possible and can exist in real life, whereas young children (4-6 years) usually report that these things are not possible and cannot exist (e.g., Shtulman, 2009). What drives this developmental difference in beliefs about what is possible?

We explored two competing accounts for this developmental shift. The development=reflection account posits that age-related differences in possibility judgements are driven by an emerging ability to reflect on modal intuitions before judging possibility. In contrast, the development=intuition account posits that these age-related differences are driven by changes in modal intuitions themselves, as a result of age-related changes in how individuals search through memory to generate these intuitions. We tested between these accounts by measuring how long children and adults took to decide whether events could occur. We anticipated that participants’ reaction times would reveal whether they reflected before judging possibility, and whether reflection increased with age.

We asked 5-to-9-year-old children (N=115) and adults (N=40) to judge whether 26 ordinary, 26 improbable, and 26 impossible events could happen and measured how long they took to respond. We found that participants were more likely with age to affirm ordinary events, ps≤.002, and improbable events, ps≤.032, whereas judgments for impossible events were stable after age 5, ps≥.230 (Figure 1). At all ages, improbable events were judged slowest and ordinary events were judged fastest, with impossible events falling in between, ps≤.001. After controlling for overall processing speed, we found that relative RTs for improbable and impossible events did not significantly differ with age, ps≥.301. Further, we found that participants were slower to make incorrect than correct responses for ordinary and impossible events, ps≤.001, but responded at similar rates for improbable events regardless of whether these events were affirmed or denied, p=.423 (Figure 2).

Lastly, we fit a drift-diffusion model to our data to examine participants’ “evidence accumulation” when judging possibility. Our model suggests that children accumulate evidence from memory in a similar manner as adults, though young children seem to have an “impossibility” bias. However, this bias is apparently due to the direction of evidence accumulation rather than a predisposed bias to deny rather than affirm events.

Our findings favor the development=intuition account over the development=reflection account. We find no evidence that adults engage in more reflection before judging possibility than children. Instead, we find that people at all ages take longer to judge the possibility of improbable events than ordinary or impossible ones. We also find that children, like adults, appear to search their memories for evidence of an event’s possibility before affirming or denying it. However, children appear biased to search for disconfirming rather than affirming evidence. We propose that a developmental shift in how memory is searched leads to a shift in modal intuitions with age, and that these intuitions are what drive possibility judgments.

Authors

• Brandon Wade Goulding, University of Winnipeg
  Presenting Author

• Farishteh Khan

• Keisuke Fukuda

• Jonathan D. Lane, Vanderbilt University

• Samuel Ronfard, University of Toronto