Myrtle was born in Birmingham, Alabama, the fifth of seven children of the farmer Riley McGraw and his seamstress wife Mary Byram.
[5][unreliable source] McGraw successfully enrolled as a graduate student[6] in the Teachers College at Columbia University, majoring in religious education.
[4] Accepting a teaching job at Florida State College for Women as assistant professor of psychology,[6] McGraw began research for her dissertation.
Her study was concerning performance differences between Caucasian and African-American children, using a battery of standard tests[1] developed by the Austrian developmental psychologist Charlotte Bühler.
She completed her dissertation, titled, "A comparative study of a group of southern white and negro infants",[9] and was awarded a doctorate from Columbia in 1931.
[1] With the onset of the Great Depression causing her concern about finding a post-doctoral internship, a former professor of McGraw advised her to talk to Fred Tilney, the director of the Neurological Institute of the College of Physicians and Surgeons of Columbia.
[3] She was appointed associate director of the Normal Child Development Study at Babies Hospital in New York City[1] by Tilney in 1930.
[3] McGraw collaborated with Tilney and neuroembryologist George E. Coghill, and incorporated the ideas of John Dewey, to try and understand the growth process.
Her work, in collaboration with others including John Dewey, advanced a focus on the reciprocal relationship between experience and the process of neural growth during early development.
[14] Her insights have influenced the work of other scientists, including Ronald Oppenheim, Gilbert Gottlieb, Esther Thelen, and Adele Diamond.