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Social recognition test on mice. The mouse tested, referred to as the reference mouse, is placed in the middle of a system comprising three chambers linked by doors. A mouse familiar to the reference mouse is placed in a cage in a chamber at one end. Another mouse, not known by the reference mouse, is placed at the other end. A trajectory analysis device quantifies the frequency of interactions between the free mouse and each of the other two mice. The test is performed on mice with Alzheimer’s disease or depression. Depressed mice show the same behaviour towards the individual they know as towards the individual they do not know. This behaviour goes against the natural exploratory tendencies of mice, which would normally tend to approach the unknown mouse.