Estimates Of Visual Slant Are Affected By Beliefs About Sugar Intake
Journal Of Vision
Does blood glucose level affect slant perception? Manipulations of blood glucose typically involve requiring participants to fast before arriving in the lab and then having them drink an unidentified drink which either contains sugar or does not. Participant beliefs regarding the drink are rarely analyzed. In prior investigations we have found that participants tend to be biased to assume that they are being given a sugar drink. Effects attributed to low blood sugar might therefore actually be due to the combination of low blood sugar with the expectation of receiving sugar. To test the role of belief we gave all of our participants diet ginger ale, but half saw it poured from a bottle with the non-diet label. To keep the experimenter blind to condition, participants were assigned randomly to soda condition by a coin flip in the presence of one experimenter who then sent the participant by elevator to complete the study with a second experimenter who did not know what condition the participant was in. After a fatiguing cognitive task mimicking the tasks often used in glucose studies, participants were taken to a steep hidden stairway and asked to judge the angle of the stairs’ ascent. A written instruction encouraged them to respond based only on what they saw. Participants who had received diet soda under the impression that it was actually regular soda gave much higher slant estimates (~50°) than those who correctly believed they had received diet soda (~40°), p <.001. A subsequent fatigue questionnaire found no differences between the two groups. Whatever the mechanism (misattribution or physiological changes induced by the expectation of sugar), these results suggest that hidden glucose manipulations are likely contaminated by expectancy or misattribution effects.
Meeting abstract presented at VSS 2012.
Vision Sciences Society Twelfth Annual Meeting
May 11-16, 2012
Morgan J. Williams , '14; Nicholas M. Ciborowski , '14; and Frank H. Durgin.
"Estimates Of Visual Slant Are Affected By Beliefs About Sugar Intake".
Journal Of Vision.