From the birth to about two years old is the sensorimotor stage, during which infants learn about the world through their senses, and their synaptic connections are sculpted by sensory experience.
As beautifully described by Stanley Graven and Joy Browne in the article Sensory Development in the Fetus, Neonate, and Infant: Introduction and Overview, “with each sensory system, the initial stimulation is internal or endogenous, but at a critical or sensitive point in development, outside stimulation and experience are needed for further development. The outside stimulation of the sensory systems must occur in appropriate sequence, intensity, and form.” They emphasized the sensory environment – the exposures to and experiencing of sound, voice, touch, movement, smell, and vision, are the processes of neurosensory development, which are critical for memory, learning and long-term brain neural circuit connections, and preservation of brain plasticity for continued learning and development over the life of the individual.
The development of the visual, auditory, olfactory, and somesthetic systems of a baby is also associated with the critical periods, during which the environmental stimuli makes the most impact to the child’s sensory development. Once the critical period is over, the environmental stimuli will no longer significantly make effect, because some irreversible changes will have taken place at the synaptic level. For instance, children who are deprived of the use of one of their senses during its critical period at the start of their lives may have permanent gaps in this sense, even if they reacquire the use of it later on. In contrast, teaching a baby to read with large print, precise and coordinated information can create simultaneous contributions to both visual and auditory pathways of the baby brain, and help the baby to build a systematic and a coherent memory of knowledge base, which consequently stimulate the baby’s intelligence, understanding and creativity at an early age.