 In 2015, he published a retrospective summary of his professional work, behavioral momentum.He is known primarily for the development of Behavioral Momentum Theory  following his 1974 article on resistance to change of pigeons' operant behavior.He received research support from the National Science Foundation and the National Institutes of Health throughout his career, most recently from the National Institute of Child Health and Human Development for application of momentum-based approaches to the treatment of severe problem behavior, conducted in collaboration with Drs.