Counterbalancing (1 of 2)

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Counterbalancing is a method of avoiding confounding among variables. Consider an experiment in which subjects are tested on both an auditory reaction time task (in which subjects respond to an auditory stimulus) and a visual reaction time task (in which subjects respond to a visual stimulus). If every subject were tested first on the auditory reaction time task and second on the visual reaction time task, then type of task and order of presentation would be confounded. If visual reaction time were lower, then there would be no way to know whether reaction time to a visual stimulus is "really" faster than to an auditory stimulus or if subjects learned something while performing the auditory task that improved their performance on the visual task. The experiment could have been designed better: Half of the subjects should have been given the visual task first and the other half of the subjects should have been given the auditory task first. That way, there would have been no confounding of order of presentation and task. Order of presentation and task would be "counterbalanced."