Using the Implicit Association Test and Choice to Measure the Within-Trial Contrast Effect in Human Adults

Abstract

When humans and nonhuman animals work hard to achieve a goal, they generally appreciate the results more than when the goal requires little effort to be achieved. The within-trial contrast (WTC) hypothesis explains this phenomenon in terms of the contrast between individuals’ relative hedonic states. We examined the validity of the WTC hypothesis by incorporating an implicit association test (IAT) as a measure of implicit preference in procedures similar to those of Tsukamoto, Kohara, and Takeuchi (Learning & Behavior, 45, 135–146, 2017), who reported emergence of the WTC effect in humans. As a procedural consideration, we also changed the following event to the presentation of a single stimulus instead of a simultaneous discrimination task. We manipulated the effort involved and difficulty of a preceding task by varying the interresponse time (IRT) in differential reinforcement with a low response rate schedule that involved a limited hold. Influences of training were tested in two measures: the choice test and the IAT. Results revealed that in the choice test participants showed significant preference for stimuli that followed the effortful task, which involved a longer IRT even though the effect size was smaller than in the previous study. However, in the IAT, we could not observe the association that the WTC hypothesis presumed. Inconsistency between the choice test and the IAT suggests that preference arising from the WTC paradigm might be caused by a factor other than a change in hedonic state, leaving the question of whether we succeeded in selecting an appropriate measure.