Stop and Ponder:

Cognitive Development: Gradual orderly changes by which mental processes become more complex and sophisticated

Critical periods:

Early Experience:

Later Experience:

Continuity vs. Discontinuity: A third major issue in developmental  psychology.

•  Does change occur smoothly over time?

Nature vs. Nurture: the debate of relative contributions of inheritance and the environment is deemed one of the oldest issues in philosophy and psychology

• Plato and Descartes supported the ideas that some ideas are inborn. 
• John Locke on the other hand argues the mind is a blank slate at birth with experience determining our knowledge. 

Critical Periods: If learning doesn't happen during these periods, it never will. \

• Are there critical periods where certain abilities need to develop?
• There is no critical period that limits the possibility of language learning by adults. Adults have more learning strategies and greater knowledge of language in general to bring to bear in mastering a second language. 
• However recent research indicates "there is a 'sensitive period' for optimal bilingual language and reading exposure and mastery"
• There is a critical period for learning accurate language pronunciation 

Critical Periods to Know
There are many specific physical, psychosocial (also called social/emotional or relating), and cognitive development milestones that most typically developing children go through. One of the earliest psychosocial critical periods is bonding. This happens in the newborn period. Holding, soothing, and caring for your baby makes it easy for her to move through this critical period. (In understaffed, overpopulated orphanages where babies do not receive the nurturing they need in this critical period, irreparable damage can be done emotionally, making it difficult for those children later in life to form close relationships.)

"Following birth there is a period of rapid brain reorganization that is a/the critical period in brain development during which children are most sensitive to environmental stimuli.”

Resource: http://www.babyzone.com/baby/baby-development/critical-periods-development_77806

Decades of research show the brain may then undergo changes that could permanently alter future functionality. However, recent studies suggest it may be possible to extend critical periods, perhaps one day offering treatment options for people who are deprived of early sensory input or experience brain injury later in life.