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Infants rationally decide when and how to deploy effort


The ability to decide whether, when and how to try is central to human learning. We investigated whether infants can make rational inferences about when and how to try on a novel problem-solving task. After learning from an adult that the task was either easy, difficult or impossible to solve, infants varied in whether, when and how they tried based on the type of social evidence that they received and on their own ongoing experience with the task. Specifically, infants formed expectations about the task, their own ability to solve the task and the experimenter’s ability to solve the task, in light of accumulating evidence across time that impacted their time spent trying, trying force, affect, and help-seeking behaviour on the task. Thus, infants flexibly integrate social input and first-hand experience in a dynamic fashion to engage in adaptive persistence.

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Fig. 1: Experimental procedure.
Fig. 2: Infants’ trying behaviour across all three indices of trying, conditions and test trials.
Fig. 3: Infants’ affect and recovery trial support across conditions.
Fig. 4: Infants’ help-seeking behaviour plotted against time spent trying.

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All code used for the analyses in the manuscript can be found at


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We thank the researchers of the Early Childhood Cognition Lab at the University of Washington for their help in participant recruitment, data collection and coding. In particular, we thank A. Sedlacek, Y. Xu, J. Lee, S. Cho, K. McManus, M. Rozaniti, K. Ventura and P. Carpentier. We also thank B. Kuykendall for his assistance with the force gauge installation and data extraction, as well as the families and infants who participated in this study. This work was supported by a grant from the Society of Research on Child Development awarded to K.L., and through a grant from NICHD (no. 1R01HD076949-01) awarded to J.A.S. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

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K.L., R.H. and J.A.S. made substantial contributions to the conception and design of the work. R.H. collected the data. K.L. coordinated data coding and performed all data analyses. J.A.S. provided critical oversight and feedback of the work. K.L. and J.A.S. wrote the manuscript. R.H. provided critical feedback.

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Correspondence to Kelsey Lucca.

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Lucca, K., Horton, R. & Sommerville, J.A. Infants rationally decide when and how to deploy effort. Nat Hum Behav 4, 372–379 (2020).

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