Almost concurrent with commercial development of the computer was psychological research and a proliferation of psychological instruments which attempt to identify the aptitudes which lead to success in selecting and training the human side of computation. Most of the early research was concerned with small groups of programming trainees in courses conducted by manufacturers or large users, and from these studies there emerged a small number of either intelligence tests or aptitude tests which gained widespread usage and acceptance as selection devices. The most widely used tests were IBM's Programmer Aptitude Test (PAT), the Wonderlic Personnel Test, and the test of Primary Mental Abilities (PMA).