When you are depressed you say that you see everything gray. This metaphor has been studied by the University of Freiburg, by a group of researchers headed by the psychiatrist Ludger Tebartz Van Elst.
The group of researchers looked for the nexus between the depressedness and the gray color, concluding that the depression causes that the contrast between the black and white colors is diluted.
To reach that conclusion, the researchers used electrodes to record the electrical activity of the retina in response to a series of flashes. Depressed patients responded to the flashes with less contrast in the photoreceptor cells of the retina.
Thus, the metaphor of seeing everything gray is not entirely incorrect, since it is closely linked with the person's state.
