Mix, a program for pseudorandomization

Abstract

In psychological experiments involving multiple trials, the order in which individual trials presented to participants influences the results obtained. For this reason, experimenters often create carefully constrained experimental lists or check randomly generated lists to avoid known causes of order artifacts (e.g., short-term stimulus or response repetition). Creating appropriately structured pseudorandom lists can be a difficult and time-consuming task in generating psychological experiments. Mix is a Windows program that can generate pseudorandomized orders according to complex, user-specified constraints. Mix can be used to generate a novel item order for each individual participant, even for complex experiments in which stimulus and/or response repetition is an experimental variable of interest, or for which automated randomization would not normally be possible. The program also contains a number of other practical features for generating files for use with a variety of experiment control software. A Mix executable for Windows, a complete manual, and terms of use are available at www.mrc-cbu.cam.ac.uk/personal/maarten.van-casteren/Mix.htm. Use is limited to academic or other nonprofit applications.