The Weekly Newsletter of MIT Linguistics

LingLunch (11/3) - Brian Leahy (Harvard)

Speaker: Brian Leahy (Harvard)
Title: Problems with Possibilities
Time: Thursday, November 3rd, 12:30pm – 1:50pm

Abstract: I will present the results of several studies that test preschoolers’ ability to talk about and think about mutually incompatible possibilities. These studies reveal systematic errors in how preschoolers (a) answer questions about what can and has to happen, and (b) form contingency plans when choosing actions in the face of multiple open possibilities. For example, when choosing between a container that must contain a prize and two additional containers that merely might contain a prize, older 2-year-olds choose a risky option half of the time. They take a risk when they could have a sure thing. This error slowly becomes less frequent with age, but is still common among 4-year-olds.

In this talk I will quickly sketch some of the behavioral results, and put an explanation on the table that accounts for the observed patterns of errors: when faced with multiple incompatible possibilities, children use simulation to generate one possible outcome and then treat that outcome as the fact of the matter. They do not mark the simulated outcome as merely possible and check whether there are other possibilities that need to be accounted for.

After sketching the behavioral results, I will present our language comprehension studies. There is no doubt that learning the English modal auxiliary system is difficult: each modal auxiliary can express many different meanings, and many different auxiliaries can express the same meaning. I will present evidence that comprehension of modal vocabulary appears late, around the same time that children start succeeding on the behavioral tasks described earlier. I will argue that the complexity of the mapping problem cannot fully account for children’s struggles. In particular, I will show that there are correlations in children’s ability to answer questions about what has to happen and their ability to apply nonmodal vocabulary like ‘all’ and ‘only’ in the modal domain. Children comprehend ‘all’ and ‘only’ by age 4, so these correlations are surprising if children’s struggles with modal auxiliaries arise only from the complexity of the mapping problem.

What is the additional problem that children face? Why is there such consistency across age in children’s ability to talk about and think about mutually incompatible possibilities? One candidate answer is that the ability to mark representations as merely possible emerges late in the preschool years, typically after age 4. Existing data do not rule out this hypothesis, and it offers a tidy explanation for all of the observed data. This motivates a direction for future research: If the ability to mark representations as merely possible is one that emerges with age, what are the mechanisms by which it emerges?