Preference tests were performed for varieties of potato chips, orange juices and chocolate chip cookies using three response protocols: the traditional paired preference test with the "no preference" option, a 9-point hedonic scale and a 6-point hybrid hedonic/purchase intent scale. The different stimuli to be assessed were presented in pairs, but putatively identical stimuli were also presented as a "placebo" pair. Performance on the placebo pair with identical stimuli provided a measure of the hidden demand characteristics of the test protocol. The presentation of the different pairs provided a measure of preference accompanied by such hidden demand effects. Comparison between the two allowed a better measure of preference per se. The order of presentation of the identical and different pairs did show occasional slight evidence of contrast effects. For the placebo "identical" pairs, a majority of consumers reported false preferences. Liking questions with the hedonic and hybrid scales elicited fewer false preferences than preference questions with the paired preference protocol. Yet, the effects tended to be slight. The 6-point hedonic/purchase intent scale exhibited the fewest false preferences in the placebo condition, and this was because of its fewer categories rather than any cognitive strategy change elicited by its different labels.