Piaget would say that this is an example of sub-stage 1 (simple reflexes) of the sensorimotor stage.
The sensorimotor stage is the first stage in Piaget's theory of cognitive development. Piaget described this stage as a period of immense growth and change. The sub-stage 1 of sensorimotor lasts from birth to 1 month. During this sub-stage, the child involuntarily responds to inborn stimuli such as sucking and looking and do not try to locate objects that vanish from sight.