The specifically human ...

The specifically human capacity for language enables children to provide for auxiliary tools in the solution of difficult tasks, to overcome impulsive action, to plan a solution to a problem prior to its execution, and to master their own behavior.
 Lev S. Vygotsky

Quotes from the same author

Learning is more than the acquisition of the ability to think; it is the acquisition of many specialized abilities for thinking about a variety of things.
 Lev S. Vygotsky
What a child can do today with assistance, she will be able to do by herself tomorrow.
 Lev S. Vygotsky
... People with great passions, people who accomplish great deeds, people who possess strong feelings, even people with great minds and a strong personality, rarely come out of good little boys and girls.
 Lev S. Vygotsky
A child’s greatest achievements are possible in play, achievements that tomorrow will become her basic level of real action.
 Lev S. Vygotsky