Paired preference "placebo" tests with "identical" stimuli: Does introducing graded preference responses affect the frequency of "no preference" responses?

Abstract

In the "placebo" control condition for paired preference testing, "identical" stimuli are presented to consumers to determine the frequency of preference and "no preference" responses induced by the hidden demand characteristics of the testing condition. As a control for bias, induced by such hidden demand characteristics, these frequencies can be compared with the actual preference frequencies of the nonidentical test stimuli to be assessed for preference. It was hypothesized that the introduction of graded preference response options might reduce the frequency of "no preference" responses in the placebo condition. Using identical yogurt stimuli with related-sample (single-group) and independent-sample (multigroup) designs, this hypothesis was not confirmed. © 2008, The Author(s).