We all know that it is easier to learn a new language or musical instrument as a child rather than in adulthood. At no other time in life does the surrounding environment so potently shape brain function – from basic motor skills and sensation to higher cognitive processes like language – than it does during childhood. This experience-dependent process occurs at distinct time windows called “critical periods”, which are times of great opportunity but also of great vulnerability for the developing brain. Early disruption of proper sensory or social experiences will result in mis-wired circuits that will respond sub-optimally to normal experiences in the future. Comparable effects are also seen for the development of vision, where if a child’s binocular vision is compromised and not corrected before the age of eight, amblyopia (‘lazy eye’) is permanent and irreversible.