Shedding new light on an old problem: The estimation of shadow sizes in children and adults

Two experiments using the ‘projection of shadows’ paradigm investigated multidimensional reasoning, implicit and explicit knowledge, and the nonlinearity concept in 5-, 9-, and 13-year-olds and adults. Participants estimated the resulting shadow lengths of differently sized objects, placed at varying distances from a light source. Experiment 1 (N = 80) revealed that, on the group level, 5-year-olds took both object size and light–object distance into account when estimating shadow size. Moreover, half of the children in this age group even considered the subordinate distance dimension. In addition, we found a large discrepancy between implicit and explicit knowledge about shadows in 5-year-olds that decreased with age. Finally, only a minority of older participants and very few younger children recognized the nonlinear relationship between light–object distance and shadow size, suggesting domain dependence of the nonlinearity concept. Experiment 2 (N = 20) predominately replicated the findings for 5-year-olds using slightly different stimuli.