Imagery paradigms: How vulnerable are they to experimenters' expectations?

The effects of experimenters' expectations on subjects' responses in imagery paradigms were investigated by leading some experimenters to believe that performance based on the use of imagery would be superior to performance based on perception. Other experimenters were led to expect perceptual superiority. Three paradigms are tested. Experiment 1 considered imaginal and perceptual acuity as functions of the size and relative brightness of the stimulus patterns; Experiment 2 compared imaginal and perceptual scanning of maps; and Experiments 3 and 4 studied the identification of rotated hands after imaginal or perceptual priming. In all the experiments, subjects' performances varied with the experimenters' beliefs, suggesting that these paradigms are sensitive to subtle influences from experimenters' tacit, unintentional cues. Experiment 4 probed the ability of observers to identify both tacit cues and the experimenters' expectations. The observers accurately assigned the experimenters' beliefs but were unable to systematically detect distinguishing and differential characteristics of the experimenters' presentations of the instructions. Analysis of taped transcriptions yielded some differences in temporal phrasing. Implications of these results are discussed.