I did a thesis in experimental nuclear physics under the direction of Samuel K. Allison.

; Mermod R. After high school Cronin stayed in Dallas and obtained an undergraduate degree at Southern Methodist University in physics and mathematics in 1951. While in graduate school he also met his wife Annette Martin whom he married in 1954.

Cronin is a member of the Board of Sponsors of The Bulletin of the Atomic Scientists. Cronin was born in Chicago Illinois and attended Southern Methodist University in Dallas Texas. Specifically they proved by examining the decay of kaons that a reaction run in reverse does not merely retrace the path of the original reaction which showed that the interactions of subatomic particles are not indifferent to time.