Reported at the National Science Teachers Association in April, 1972, in New York City, this investigation was designed to test the importance of pupil manipulation of science materials in the attainment of science process skills for kindergarten and third grade students. It has focused on a specific kind of learning task: acquisition of science process skills. Direct manipulation of materials by kindergarten children was determined to significantly increase their attainment of process skills. However, the attainment of science process skills by third grade children directly manipulating science materials was not significantly better than the attainment by children not manipulating these materials. It was concluded that the influence of direct, first-hand, manipulative experiences in the development of process skills may well be more important for the early primary grade child than for older children. (CP)