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Mix and Match

Mix and Match are tools to support experimental research. Mix will allow experimental stimuli to be pseudo-randomised, according to constraints supplied by the user in a simple script. Match can match the conditions of factorial experiments. Both utilities have the ability to significantly speed up the development, and even improve the quality and power of your experiments.

Papers were published in Behavior Research Methods for both utilities by me and Matt Davis. Please quote these papers if you make use of our tools in your research.


In psychological experiments involving multiple trials, the order in which individual trials are 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. 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. Use is limited to academic or other nonprofit applications.

The MIX program, with a manual, can be downloaded here

The BRM paper can be downloaded here: Mix, a program for pseudorandomization


In most experiments that involve between-subjects or between-items factorial designs, the items and/or the participants in the various experimental groups differ on one or more variables, but need to be matched on all other factors that can affect the outcome measure. Matching large groups of items or participants on multiple dimensions is a difficult and time-consuming task, yet failure to match conditions will lead to suboptimal experiments. Match automates this process by selecting the best-matching items from larger sets of candidate items. In most cases, the program produces near-optimal solutions in a matter of minutes and selects matches that are typically superior to those obtained using hand matching or other semiautomated processes. The paper reports the results of a case study in which Match was used to generate matched sets of experimental items (words varying in length and frequency) for a published study on language processing. The program was able to come up with better-matching item sets than those hand-selected by the authors of the original study, and in a fraction of the time originally taken up with stimulus matching.

The MATCH program, including a manual, can be downloaded here

The BRM paper can be downloaded here: Match: a program to assist in matching the conditions of factorial experiments

Please note:

These tools are no longer maintained and code is provided ‘as is’ for archival purposes without support. There are other, more flexible, methods for achieving similar goals that have been described in recent papers, such as Slivkoff & Gallant (2021, Neuron).