The ultimate expression of applying behavioral principles is instruction, particularly instruction of students who have learning challenges and are often therefore hard to teach and motivate. Siegfried (Zig) Engelmann has an unparalleled record in this arena. The instructional programs authored by Engelmann have been used with more than 10 million children since the late 1960s. Engelmann's programs have been used in both regular education and special education classes. The majority of regular education use has been in high-poverty schools. The programs have been used to serve special education children with many kinds of disability, including children with Down syndrome, hearing loss, behavior problems, and mental retardation. When properly implemented, Engelmann's instructional techniques have produced astonishing performance gains.

Engelmann was raised in Chicago. In 1955, ...