1. Department of Biological Sciences, and Program in Cognitive Science (C.J.S.), Lehigh University, Bethlehem, Pennsylvania 18015;
2. Department of Psychology (L.R.-H.), University of Massachusetts, Amherst, Massachusetts 01003;
3. Departments of Integrative Biology and Physiology, Ecology and Evolutionary Biology, and Laboratory for Neuroendocrinology (B.A.S.), University of California-Los Angeles, Los Angeles, California 90095