Social Science Statistics Blog

One question is whether children are capable of using the difference between evidence from observations and evidence from intervention (manipulation) to build a different causal structure. The well-named "theory theory" theory of development suggests that children are like small scientists and should therefore be quite sophisticated causal reasoners at an early age. To test this, Schulz, Kushnir, & Gopnik [pdf showed preschool children a special "stickball machine" consisting of a box, out of which two sticks (X and Y) rose vertically. The children were told that some sticks were "special" and could cause the other sticks to move, and some weren't. In the test condition, children saw X and Y move together on their own three times; the experimenter then intervened to pull on Y, causing it to move and X to fail to move. In the experimental condition, the experimenter pulled on one stick (X) and both X and Y moved three times; a fourth time the experimenter pulled on Y again, but only it moved (X was stationary).

The probability of each stickball moving conditioned on the other are the same in both cases: however, if the children reason about causal interventions, then the experimental group -- but not the control group -- should perceive that X might cause Y to move (but not vice-versa). And indeed, this was the case.

Children are also good at detecting interventions that are obviously confounded, overriding prior knowledge, and taking base rate into account (at least somewhat). As I said, this is a huge (and exciting) literature, and understanding people's natural propensities and abilities to do causal reasoning might even help us address the knotty philosophical problems of what a cause is in the first place.