Sensing the Coherence of Biology in Contrast to Psychology: Young Children’s Use of Causal Relations to Distinguish Two Foundational Domains


  • This research was supported by the National Institutes of Health Grant R37-HD023922 to Frank C. Keil. We thank the staff, parents, and students at Bell-Graham, Gales Ferry, Guilford Lakes, and Thalberg elementary schools for their support. Special thanks to Yaw Anim, Amy Hart, and Jared Aguirre for their assistance with this research.

concerning this article should be addressed to Jane E. Erickson, Department of Psychology, Yale University, 2 Hillhouse Ave., New Haven, CT 06520-8205. Electronic mail may be sent to


To what extent do children understand that biological processes fall into 1 coherent domain unified by distinct causal principles? In Experiments 1 and 2 (= 125) kindergartners are given triads of biological and psychological processes and asked to identify which 2 members of the triad belong together. Results show that 5-year-olds correctly cluster biological processes and separate them from psychological ones. Experiments 3 and 4 (= 64) examine whether or not children make this distinction because they understand that biological and psychological processes operate according to fundamentally different causal mechanisms. The results suggest that 5-year-olds do possess this understanding, and furthermore, they have intuitions about the nature of these different mechanisms.