A computerized technique for estimation of the reaction time of motor responses to visual stimuli was advanced. The testing includes three stages. The following kinds of reactions were studied: simple reactions at the first stage, simple choice between 2 and 4 alternatives at the second stage, and, finally, reactions of the complex choice between 2 and 4 alternatives at the third stage. The authors think that each kind of reactions reflects specific components of child's sensorimotor activity. It is planned to study the rate of ontogenetic development of different links included into the functional system of voluntary sensorimotor reactions (perceptual, motor, decision making and others) using the proposed technique.