The comparison of Condition A with Condition B for learning lists of nonsense syllables (see Chapter 21) sometimes may best be made by following an ABBA order to balance out the factors of inexperience at the beginning and boredom at the end of the experiment. Similarly, sensory experiments may be designed in such a way that progressive changes in adaptation or alertness are also counterbalanced. This may often be done by randomizing the order of presentation of stimuli of different strengths.