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THE PERCEPTION OF SOCIAL CAUSALITY BY 3- TO g-MONTH-OLD INFANTS

Rachel Morgan and Philippe Rochat

Emory University, Atlanta, GA 300322

Previous research has shown that adults perceive meaningful relationships in the motion of abstract objects. They attribute causal (Michotte, 1963) social, and intentional relationships to moving geometric figures (Heider & Simmel, 1944; Bassili, 1976). In recent research (Rochat, Morgan, Carpenter, in press), it was found that infants as young as three months discriminate between the movements of two discs on a computer screen that never contact each other but that either move dependently (chase event) or Independently of one another (non-chase event). The present study expands this research by investigating the devebpmental emergence of an ability to detect a role reversal between two abstract enttties chasing one another. In particular, we tested infants ranging in age from 3- to 9-months of age for evidence of an ability to discriminate a role reversal between chaser and chasee. This discrimination is considered to be indicative of an intentional stance in the development of early social understanding.

Fifty-one healthy, full term infants were tested. Thirteen were 3-4-month-olds, 13 were 5-6- month-ok&, 12 were 7-8-month-old% and 13 were 9-month-olds. An habituation/dishabituatttn paradigm was used. Infants were seated in their parents’ laps facing a large computer monitor. Parents wore opaque sunglasses to avoid looking at the display. An experimenter stood behind the stimulus display pressing the keyboard each time the infants looked towards the monitor. A computer program recorded the number of seconds looking and signaled the experimenter when habituation trials ended and test trials began. An additional experimenter, sitting behind the infant controlled a keyboard that changed the display presented to the infants on the computer screen. Infants saw two types of displays: a red disc chasing a blue disc or the reverse of this scenario (the test trials). Both discs were identical in size (1.7 cm in diam.) only identifiable by either their red or blue color. The stimuli consisted of repeated 7 second chase events (computer generated by a random algorythmic seed) in which one disc chased the other but never came Into contact with it. In each event, when the chaser reached a set distance from the chasee, the latter accelerated away at a faster cruising velocity until it reached a “relax” distance and the sequence began again.

A one-way ANOVA conducted on ratio scores comparing test trials to habituation trials for the 4 groups of infants revealed that only the 9-month-olds looked significantly longer at the role reversal test trial than the younger groups. A ratio score was computed as the duration of the first test trial divided by the mean of the last 3 habituation trials (i.e., infants scoring a ratio over 1 .O showed more looking to the test). In addition, a correlation performed on the ratio scores as a function of age in days revealed a steady progression in infants’ tendency to look longer at the role reversal test trials compared to the habituation trials (r = .416, pc .0024) with a dramatic increase in the proprortion of individuals who noticed the change by 275 days (g-months). The results suggest that by g-months, infants reliably detect the role~reversal in the chase event, but not before, although younger infants show a progressive trend towards such detection. The results support an important developmental transition by 9months in the development of social cognition and suggest that by this age, the relative movements of animately moving objects specify social meaning to young infants.

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Michotte, A. (1963). The Per-n of Cau8&ty. London: Methuen. Rochat, P., Morgan, R., & Carpenter, M. (in press). Young infants’ sensitivity to movement

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