http://www.quadcitychess.com/benefits_of_chess.html

In a 1973-74 Zaire study, conducted by Dr. Albert Frank, employing 92 students, age 16-18, the chess-playing experimental group showed a significant advancement in spatial, numerical and administrative-directional abilities, along with verbal aptitudes, compared to the control group. The improvements held true regardless of the final chess skill level attained.