We estimate a structural model of endogenous short-run human capital invest- ment focusing on a learner’s leisure-study choices, influenced by external costs/benefits and two key internal factors: learning productivity and willingness to engage in study activity. Our novel self-investment framework rigorously quantifies models of learning that have existed in the psychology literature for decades. Our identification strategy combines panel data and study-incentive variation to point identify student-level parameters. Empirically, we find that idiosyncratic productivity and motivation traits are uncorrelated, and that low productivity is the stronger predictor of academic struggles, not low motivation. We investigate the influence of external factors on student learning and find that school quality affects it through 3 channels: augmenting productivity, augmenting skill production TFP, and by altering the mapping between learning activity and permanent skill gains.