Self-Sensitivity in Fetal Development

It is an inconvenient truth that the onset of behavior is before birth. In all the mammalian species, for example, behavior begins in utero, hidden within the mother’s body. This simple bit of biology has made it difficult to observe or to access fetuses, leaving the beginnings of behavior to the imagination or, even worse, allowing it to be forgotten or ignored. Such truncation of perspective probably helped many to consider behavioral capabilities first seen at birth in a separate, special category termed inborn or “innate.” Gradually, however, behavioral embryologists began to accrue observations of fetal behavior (e.g., Narayanan, Fox, & Hamburger, 1971). They learned how to probe into fetal behavior with questions and methods to obtain rudimentary answers. The early pioneers were joined by some developmental psychobiologists, who brought other traditions to the area (Krasnegor & Lecanuet, 1995; Smotherman & Robinson, 1995). When studying behavioral embryology in oviparous (egg-laying) species, the living embryo is virtually presented to the investigator, who can cut a window into the eggshell or gain direct access to the embryo within it (e.g., Gottlieb, 1985; Kuo, 1967). With viviparous species, investigators bring the fetus out of the mother’s body, carefully preserving the umbilical and placental connections. These dramatic preparations allow researchers to see directly, manipulate directly, and measure more directly, which effectively gave birth to a new field of study. My comments here are inspired mostly by the impressive and important report by Robinson, Kleven, and Brumley (this issue). This research is a contribution to a continuing literature on rat behavioral embryology and, indeed, to developmental studies in general.