Seashore was born in Mörlunda, Hultsfred Municipality, Kalmar County, Sweden and emigrated to the United States in 1870. He graduated from Gustavus Adolphus College, St. Peter, Minnesota in 1891. Seashore attended Yale when that school had just opened its psychology department under George Trumbull Ladd. In 1895, Seashore was awarded the school’s first PhD in psychology for his dissertation on the role of inhibition in learning.
After a fellowship at Yale, he accepted a position at the University of Iowa where he spent the remaining 50 years of his life. He was made chairman of the Department of Psychology and dean of the Graduate School.
Seashore was particularly interested in Audiology, the Psychology of Music, the Psychology of Speech and Stuttering, the Psychology of the Graphic Arts, and Measuring Motivation and Scholastic Aptitude. His complete publication list from 1893 to 1949 includes 237 books and articles.