To test their idea the researchers developed a game based on some scenes from Duke Nukem, a game in which players navigate around a virtual town. The participants, who were already familiar with the town, were asked to find their way to as many landmarks as possible within a set amount of time.

Depressed people found their way to an average of 2.4 locations compared with 3.8 locations for healthy controls. Indeed, the more depressed a person was, the lower the score (The American Journal of Psychiatry, vol 164, p 516). Gould hopes the test may eventually provide a quantifiable measure of depression.