Culture impacts thought and speech development because it defines, at least partially, the experiences and types of experiences that children have. For example, many cultures still restrict the social activities and career opportunities for women; in remote parts of the rural south, in the Middle East, Asia, and South America, women get little if any education, stay home, help their mothers, get married, raise the children, etc. The experiences are primarily anchored to the domain of domestic life.
Contrast this to a women who has a less-fettered existence: she goes to school, has social interactions beyond her family (in some cases, with males), she goes on to higher education, enters a career, etc.
These two cultures manifest totally different outcomes as adults; the standards that they operate within are imbued in the children as they are reflected by the adults who raise and lead them. Even before they can think or speak, children’s experiences are being shaped by their culture. Infants often spend most of their time with mothers, aunts, grandmothers and other females; in some cultures, fathers have little physical contact with their newborns.
Thought develops on the basis of experience; speech develops in an attempts to communicate within those experiences. A small boy might be given a picture book to keep him occupied while mother is busy, even though he cannot read. But would the same mother give a book to a small girl, knowing that she will never have a use for books? Possibly not.
The impact of culture is often subtle; but always strong. We can develop programs to change this. But the programs’ progress will be slow and success is uncertain. I heard a great quote last week at EDUCAUSE: “Culture eats strategy for breakfast every day.”