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.