Between 1880 and 1930, entrepreneurial individuals in academic psychology and engineering converged on a common interest in the human side of enterprise. Both disciplines subsequently overlapped in marketing their professional business services. Separating from academic psychology, applied psychologists alluded to being "human engineers" offering a personnel selection technology to industry. Conversely, scientific management diverged from engineering with psychological claims of fostering a "mental revolution" of management-labor cooperation. Although psychology's testing technology was accepted, scientific management's psychological claims were challenged. This article details the entrepreneurial individuals (e.g., F