The importance of instrument firms in the development of psychology, and science in general, should not be underestimated since it would not have been possible for various leading psychologists at the turn of the twentieth century to conduct certain experiments without the assistance of instrument makers, as is often the case today. To illustrate the historical perspective introduced here, the example of Alfred Binet is taken, as he is an interesting case of a psychologist working in close collaboration with various French instrument designers of the time. The objective of this article is twofold: (1) to show the considerable activity carried out by early psychologists to finalize new laboratory instruments in order to develop their research projects; (2) to reassess the work of a major figure in French psychology through his activity as a designer of precision instruments. The development of these new instruments would certainly have been difficult without the presence in Paris of numerous precision instrument manufacturers such as Charles Verdin, Otto Lund, Henri Collin, and Lucien Korsten, on whom Binet successively called in order to develop his projects in the field of experimental psychology.