Besides responses to the target pair of stimuli being tested in a paired preference test, comparison with responses to a putatively identical "placebo" pair can be used for a test of significance, to determine whether the response frequencies elicited by the target pair are different from those that would be obtained had there been no preference. Yet, preference responses elicited by the placebo pair can also be used as a way of identifying consumers who bias avoided the "No preference" option and thus generated biased response. Such consumers can then be eliminated. Yet, using this approach greatly reduces the sample size. However, using some response options associated with purchase intent rather than liking can reduce the number of consumers that are eliminated. This was confirmed for potato chip, milk and orange juice stimuli. From psychology, the concepts of operational preference and types of response bias appropriate to preference testing were introduced and discussed.