For more details see:

http://www.apa.org/research/action/segregation.aspx

American Psychological Association, May 28, 2003, Revised July 2007

Cited Research

Clark, K. B., & Clark, M. K. (1939). The development of consciousness of self and the emergence of racial identification in Negro preschool children. Journal of Social Psychology, 10, 591-599.

Clark, K. B., & Clark, M. K. (1939). Segregation as a factor in the racial identification of Negro pre-school children: A preliminary report. Journal of Experimental Education, 8, 161-163.

Clark, K. B. & Clark, M. K. (1940). Skin color as a factor in racial identification of Negro preschool children. The Jou...

Based on Research by Mamie K. Clark, Ph.D. and Kenneth B. Clark, Ph.D. Psychology Science Minute written by American Psychological Association, adapted by Juanita N Baker, Ph.D.

Psychology Research has contributed to the law of our land.

Psychologists Mamie and Kenneth Clark in the 1940s investigated black children’s racial identification and preference. Using drawings and dolls of black and white children, they asked Black pre- and elementary school children to pick which drawing or doll they preferred and which looked most like them and matched their own skin color. The Clarks found that Black children often chose the white doll. They drew and colored the child drawing a shade lighter than their own skin, illustrating that they viewed white as good and pretty, but black not so. 
Quoting the
Clarks: Many Black children, “indicate a clear-cut preference for white. It is clear that the Negro child, by five, is aware of the fact that to be colored in contemporary American society is a mark of inferior status. A child accepts as early as six, the negative stereotypes about his own group.”

With the help of the Clark’s research findings, that illustrated the effect of prejudice and discrimination on a child’s development, the plaintiffs in Brown v. Board of Education were able to show that segregated schools were inherently unequal, leading to the Supreme Court’s unanimous decision that segregated schools are unconstitutional.