@article {1808,
	title = {Continuous representations of action efficiency in infancy},
	year = {2016},
	month = {01/2016},
	abstract = {<p>In reasoning about action, infants apply the principle of efficiency, recovering attention when agents pursue goals using curvilinear paths if a straight path was available (Csibra et al., 1999). What representations support these capacities? The present research explores the hypothesis that infants represent cost as a continuous function within a naive utility calculus (Jara-Ettinger et al., 2015) by testing 6-month-old infants{\textquoteright} expectations for efficiency using action trajectories differing in curvature. In Study 1, we habituated infants to a rational agent, whose goal-directed actions were constrained by tall barriers, and then measured how long infants attended when the same agent navigated over a novel, low barrier efficiently or inefficiently. In Study 2, we asked whether infants recover attention to inefficient actions solely on the basis of low-level perceptual properties by repeating Study 1 but moving the barrier beyond the agent{\textquoteright}s goal, causing all actions to be unconstrained. In Study 3, we used the unconstrained habituation events from Study 2 and the constrained test events from Study 1 to test whether infants expect an irrational agent to act efficiently given a novel constraint. Across these studies, we demonstrate that 6-month-olds (1) analyze trajectories of goal-directed action differing in curvature on the basis of their efficiency, (2) expect minimally costly action given novel constraints, even for previously irrational agents, and (3) differentiate between these actions on the basis of efficiency, not low-level perceptual differences in height or motion. Our findings indicate that continuous cost representations support an early, robust expectation for rational action.\&nbsp;</p>
},
	author = {Shari Liu and Elizabeth S Spelke}
}
