Children between eight and twelve years of age were administered a battery of object and viewer transformation tests.
Analyses of variance showed that performance on these tasks increased with age.
Confirmatory factor analysis revealed no differentiation of object and viewer transformation ability under 10.5 years of age.
A dissociation of object and viewer transformation ability was observed between 10.5 and 12 years of age.
Spatial functions specialize between 8 and 12 years of age, reflecting an interesting time window for interventions.