The Development of the Concepts of Effort and Ability, Perception of Academic Attainment, and the Understanding That Difficult Tasks Require More Ability

John G. Nicholls, The Development of the Concepts of Effort and Ability, Perception of Academic Attainment, and the Understanding That Difficult Tasks Require More Ability, Child Development, Vol. 49, No. 3 (Sep., 1978), pp. 800-814