Stevens was born in Ogden, Utah to Stanley and Adeline (Smith) Stevens and educated in Latter-day Saint-affiliated schools in Salt Lake City, Utah. He spent much of his childhood in the polygamous household of his maternal grandfather Orson Smith. At the death of his parents in 1924, he spent the next 3 years on an LDS mission in Switzerland and Belgium. He attended the University of Utah from 1927 to 1929 and Stanford University for the next two years, graduating with an A.B. in psychology in 1931.