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THE GRIGINS GF AN IN’IUITIVR BIOLOGY IN INFANCY

Rebecca Hill & Rosemary Rosser, Department of Wucational Psychology, The University of Arizona Tucson, AZ 85721

The “theory” theory perspective on cognitive development presupposes that individuals are able to slice up the world into coherent conceptual chunks and construct domain-specific explanatory systems uniquely applicable to those chunks. A prerequisite to theory construction is the identification of the set of entities, distinct from other entities, to which a particular explanatory belief system would apply. Recent literature indicates that by early toddler years, youngsters are well on their way to differentiating “object*’ things from “mind” things--classes of entities to tiich an intuitive physics and a theory of mind would respectively apply. The literature also points to an early emerging intuitive biology, a theory of “live” things, based initially on a differentiation of objects whose behavior is explainable by external factors (eg., forces) from those whose behavior is attributable instead to internal factors. The question addressed in this research is whether infants are able to discriminate “live“ things from “not-live” things, an ontological distinction which would seem prerequisite to the construction of a rudimentary biology. Gntological kind is a stable property of entities. Except in fairy tales and Ghostbuster movies, inanimate physical entities remain so and do not switch ontological classes to become biological entities. To the adult and older child, such an ontological leap would be construed as an anomaly, an irrpossible event. Would an infant react similarly?

To address this question w adapted an object occlusion task designed for assessing infants’ object me.mory and concept of object identity. In our version: (1) The infant observes a target object presented on a lighted stage, (2) the object is occluded, and (3)after a brief delay, the occluder is removed. The expected (CONTROL) event is that the original object will remain in the location where it was occluded. Experimental variations entail the generation of unexpected events, seemingly *‘inpossible” object changes. Infants reactions to these changes (as signaled by increased looking time) to the violation of expectations, is observed. Six- and g-month-old babies were exposed to a physical object engaged in a rigid motion (rotation). Subsequently, the target object was occluded, a delay (15sec) was imposed, then the occluder was removed. The revealed object could be either (1) the same object undergoing a different rigid motion (translation), MOTIGN CHANGR), (2) an new object, also non-biological undergoing the original motion (GBJRCT CHANGR), or (3) an new object live and biological carrying on its own characteristic motion (ONTOLOG ICAL CHANGE). All objects were presented in identical, cage-like containers. The aspect of the stimli relevant to the conceptual question: The target object (toy-white-hamster) was featurally identically to the live object (live-albino-hamster) and featurally different from the other non-biological object (toy-green-truck), Looking time (LT) to the change event was contrasted with LT generated in a control condition and with an absolute criterion expected under the null hypothesis. An analysis of variance on the LT data indicated no effect for age. For both age groups: (1) The MGTION CHANGR did not lead to a significant increase in LT. (2) The OEUEXT CHANGE did yield a weak but signif icant increase in LT (p<. 051, and (3) the WlULGGICAL CHANGE also yielded a significant effect (p<.Ol). (4) The GNTUWGICAL CMNGR resulted in a significantly greater increase in LT than did the OBJECT CHANGR (p<.O5) even though the target object and the live object were featurally identical. Ancillary data (reaching) were consistent with object discrimination on the basis of ontological kind. These data suggest that by six-months of age, infants do differentiate biological entities from other entities and that such a difference in kind is in fact highly salient.