SAGE Publications Ltd,

A molecular geneticist advised me recently that no study of a new strain of mutant mice would survive peer review unless the Open Field Test has been used to profile their locomotor (ambulatory) activity. This would certainly help to explain why the number of publications extracted by keywords ‘open field ’ with ‘locomotor activity ’ has increased fourfold in the last 10 years, but it’s worry-ing. Although it is not at all certain what the Open Field Test actu-ally measures, it is absolutely clear that it does not give a simple index of the status of motor output. It is easy to see why the Open Field Test is so alluring. The modest approach is to score the number of times the rodent crosses a matrix of lines that has been painted on the floor of the arena. Higher-tech labs have the option of using activity meters, which record the number of times the animal intercepts parallel beams of light that span the arena. When two adjacent infrare