Fig. 1: Motivated Learning Task.
Example trials of the Motivated Learning Task for the learning and test phases of experiment 1, 2 and 3. During the learning phase, participants had to memorize 128 images. Each image was associated with a reward presented before the image (gems in a treasure chest in experiments 1 and 2, or cash (GBP), displayed as pictures of a bank note/coin in experiment 3). Trials of the Motivated Learning Task were separated by three trials of a flanker task to prevent rehearsal. During the test phase, participants had to determine whether the image they were presented with was “old” (i.e., shown during the learning phase) or “new” (i.e., not shown during the learning phase) and indicate their confidence in their choice on a 3-point likert scale (i.e., “guess”, “sure”, “very sure”). In experiment 1, if participants said that an image is “old” they were asked to indicate which reward they thought the image was associated with. In experiments 2 and 3, the reward was shown before the picture also in each trial of the test phase. In experiment 2, the reward was either congruent or incongruent to the reward shown to the participant during the study phase. In experiment 3, rewards shown during the test phase were always congruent to the reward shown during the study phase. In all experiments, participants who made a hit were rewarded the amount associated with the image. For a correct rejection, they received the mean value of all possible rewards and if they made an incorrect decision, they lost the mean value of all possible rewards. The example stimuli shown for experiments 1 and 2 have been uploaded under the Public Domain Mark 1.0 Universal license by Bureau of Land Management California and Jeff Hollet on Flickr. The example stimuli shown for experiment 3 are photographs taken by Gordon Feld. The graphics used as fixation markers and reward displays were drawn by the Juliane Nagel.
