Definition of "manipulative"

As in much of biology, the most satisfying truths in ecology derive from manipulative experimentation. Tinker with nature and quantify how it responds.

2012 January, Robert M. Pringle, “How to Be Manipulative”, in American Scientist‎, volume 100, number 1, archived from the original on 3 October 2013, page 31

Some children need manipulatives to learn math basics, Dr. Clements said, but only as a starting point.

2008 April 25, Kenneth Chang, “Study Suggests Math Teachers Scrap Balls and Slices”, in New York Times‎