Slater's father, born in Virginia, who had been an undergraduate at Harvard, became head of the English Department at the University of Rochester, which would also be Slater's undergraduate alma mater. Slater's youthful interests were with things mechanical, chemical, and electrical. A family helper, a college girl, finally put a name (then little-known as a subject) to his set of interests: "physics". When Slater entered the University of Rochester in 1917 he took physics courses and as a senior assisted in the physics laboratory and did his first independent research for a special honors thesis, a measurement of the dependence on pressure of the intensities of the Balmer lines of hydrogen.