Final answer:
Hugo Münsterberg was the industrial psychologist who was president of the American Psychological Association at the beginning of World War I.
Step-by-step explanation:
The industrial psychologist who was president of the American Psychological Association at the beginning of World War I was Hugo Münsterberg. Münsterberg was a pioneer in the field of industrial psychology and made significant contributions to the study of employee selection, training, and effective advertising. He published the book Psychology and Industrial Efficiency in 1913, which covered these topics.