Sensitivity to Confounding in Causal Inference: From Childhood to Adulthood

Sensitivity to Confounding in Causal Inference: From Childhood to Adulthood E. Christina Schofield (christis@ucla.edu) Department of Psychology, Box 951563 Los Angeles, CA 90095-1563 USA Patricia W. Cheng (cheng@psych.ucla.edu) Department of Psychology, Box 951563 Los Angeles, CA 90095-1563 USA Abstract confounding when there are two candidate causes for a novel outcome. A necessary condition for correctly assessing causality is the absence of confounding causes. This set of experiments assesses whether people are sensitive to confounding when they infer causation . Two stories were constructed, one in which two candidate causes and an outcome perfectly covaried (confounded), and one in which one candidate cause occurred independently of a second candidate cause that perfectly covaried with an outcome (unconfounded). If people reason by forming contrast groups that hold alternative causes constant, then in the confounded case, subjects should say that it is impossible to determine causality when two candidate causes are confounded. In the unconfounded case, subjects should be able to say that the candidate is causal. If people are not sensitive to confounding, then they should attribute causality to both candidates in the confounded case, and the results for the target candidate should be the same as those in the unconfounded case. This experiment was conducted with children and adults. Children saw one of the two conditions, while adults saw both conditions. Both children and adults make a distinction between confounded and unconfounded causes when making attributions of causality. Our results As well as being a potential means of improving science instruction and for examining whether children assess causality in the same manner as adults, assessing children’s sensitivity to confounded causes is also important for differentiating between two models of causal attribution: the unconditional ∆P model (Jenkins & Ward, 1965), and the focal sets approach (Cheng and Novick, 1992). Under the unconditional ∆P model, people compare the frequency of e, an effect of interest, when c, a potential cause, is present, with the frequency of e when the potential cause is not present: ∆P = P(e|c) – P(e|~c) show that children are able to state the indeterminacy of confounded causes at an age much earlier than previously documented. Introduction One view of how children learn is that they approach the world as scientists and form theories about the world (e.g. Gelman, 1996) using information about variation and covariation to establish causal connections (Gopnik, Sobel & Schulz, 2001). Further, they intervene upon the world in order to discover these relationships (Schulz, 2003). Although children may have misconceptions in their explanations, as when a child states that he thinks God made the sun out of gold and lit it with fire (Siegler, 1998), the presence of such misconceptions does not mean that children are unable to use the data present in the environment to form correct causal attributions. Given that adults have had many more experiences than children, we should not expect children’s theories to be the same as adult’s theories, especially for complex phenomena. What is important is whether the same process is utilized when determining causality. In particular, this paper seeks to examine whether both children and adults are sensitive to If ∆P = 0, then the candidate is considered noncausal; if ∆P is noticeably greater than 0, then the candidate is thought to cause the outcome, and if ∆P is noticeably less than 0, the candidate is thought to prevent the outcome. In the unconditional version of this model, people ignore confounding and pool over all the information known about the candidate cause. Using this formulation, if both candidate causes perfectly covary with each other and the outcome, then both will be judged as causal. Under the focal sets approach, the same formula can be used, but is evaluated only when comparing across groups where alternative causes are held constant. If people utilize the focal sets approach, they could make a determination when no confounding was present, but would be indeterminate in the case of perfect covariation because no focal set could be formed. One study looking at third, sixth and ninth graders, as well as non college young adults and undergraduate college students found that before the ninth grade, students were unlikely to state that there was insufficient evidence to determine causality when there is confounding (Kuhn, Amsel, O’Loughlin, 1988). But, these experiments involved causes for which the students were likely to have prior theories, and people interpret ambiguous data in ways that are consistent with their prior beliefs (Darley & Gross, 1983). Kuhn et. al. do not indicate whether students who did not notice the indeterminacy were answering in a manner consistent with their prior theory. Also, this set of studies