An extensive literature search revealed three prior reviews and five meta-analyses focused on comparing manipulative use to traditional instructional methods in mathematics.However, findings and conclusions differed in important ways and suggested variables potentially associated with differential intervention effects. Early reviews (i.e., Fennema, 1972; Suydam & Higgins, 1977) suggested that manipulatives supported student understanding of underlying mathematical concepts but reached different conclusions about differential effects based on student grade level. An annotated bibliography compiled by Gerling and Wood (1976) listed 103 research studies conducted from 1970 to 1975 on the use of manipulatives, but no
conclusions were drawn about the effectiveness of manipulative use on learning.