Publications of Koos, O.

One-year-old infants use teleological representations of actions productively

Two experiments investigated whether infants represent goal-directed actions of others in a way that allows them to draw inferences to unobserved states of affairs (such as unseen goal states or occluded obstacles). We measured looking times to assess violation of infants' expectations upon perceiving either a change in the actions of computer-animated figures or in the context of such actions. The first experiment tested whether infants would attribute a goal to an action that they had not seen completed. The second experiment tested whether infants would infer from an observed action the presence of an occluded object that functions as an obstacle. The looking time patterns of 12-month-olds indicated that they were able to make both types of inferences, while 9-month-olds failed in both tasks. These results demonstrate that, by the end of the first year of life, infants use the principle of rational action not only for the interpretation and prediction of goal-directed actions, but also for making productive inferences about unseen aspects of their context. We discuss the underlying mechanisms that may be involved in the developmental change from 9 to 12 months of age in the ability to infer hypothetical (unseen) states of affairs in teleological action representations. (C) 2002 Cognitive Science Society, Inc. All rights reserved.

Goal attribution without agency cues: the perception of 'pure reason' in infancy

The proper domain of naive psychological reasoning is human action and human mental states but such reasoning is frequently applied to nora-human phenomena as well. The studies reported in this paper test the validity of the currently widespread belief that this tendency is rooted in the fact that naive psychological reasoning is initially restricted to, and triggered by, the perception of self-initiated movement of agents. We report three habituation experiments which examine the necessary conditions under which infants invoke a psychological principle, namely the principle of rational action, to interpret behaviour as goal directed action. Experiment 1 revealed that the principle of rational action already operates at 9 (but not yet at 6) months of age. Experiment 2 demonstrated that perceptual cues indicating agency, such as self-propulsion, are not necessary prerequisites for interpreting behaviour in terms of the principle of rational action. Experiment 3 confirmed that this effect cannot be attributed to generalisation of agentive properties from one object to another. These results suggest that the domain of naive psychology is initially defined only by the applicability of its core principles and its ontology is not restricted to (featurally identified) object kinds such as persons, animates, or agents. We argue that in its initial state naive psychological reasoning is not a cue-based but a principle-based theory. (C) 1999 Elsevier Science B.V, All rights reserved.