ABSTRACT
The genesis was described by psychologists based on the opposition of instinct and intelligence. The instinctive tendency prompts the subject to go straight to the point, with the risk of hitting the obstacle the experimenter placed in the way. Intelligence shows in the ability to make detours. Guillaume and Meyerson using animal experiments including chimpanzees, described what constitutes the difficulty of detours, and regarded the tool as a form of a particularly complex detour. While in the early XXth century some psychologists started to measure intelligence, others, on the contrary, attempted to describe it and furthermore, to find tangible indicators to support their description. The theory of evolution motivated them in studying prehistorical anthropological works, first, and secondly, animal intelligence. Research in animal psychology helps make comparisons. The genesis of the tool can also be studied in the child. From a developmental perspective, the making of a tool is obviously a significant step in evolution.
