Send Orders of Reprints at bspsaif@emirates.net.ae The Timing Accuracy of General Purpose Computers for Experimentation and Measurements in Psychology and the Life Sciences

Abstract: General purpose computers find increased use within behavioural, psychological, and neuroscientific experimentation, which raises concern for the timing accuracy that can be obtained with such systems. Here, we assessed the timing accuracy of such machines, considering both differences between different hardware and different versions of the Windows™ operating system (OS); Windows XP, Vista and Windows 7. The variability varied widely across machines and OS versions. The indeterministic variability within each OS and computer combination was mostly within +/-30 ms, and had a non-normal distribution with many small deviations and few large deviations. These large deviations are a characteristic feature that seems to constitute occasional additional delays up to about 150 ms. Thus, although measurements recorded from a general purpose PC running Windows should have an accuracy of -30 to +50 ms, occasionally larger variations suggest that experiments need a large test base to avoid significant distortions of the results