3.2.2.4. Procedure.
The procedure was in its entirety administered through a computer system. Participants were tested in groups of 10e16 in a laboratory setting. Participants were randomly assigned to one of the four groups, and each session lasted for about 1 h.
Participants received an introduction to the computer-based procedures and were asked to follow the instructions on the screen. After spending 5 min completing the demographic questionnaires, the participants were presented either the positive or the neutral video in order to externally induce emotions. Participants then completed the positive affect schedule for the first time (PAS1). Next, the multimedia instruction with either neutral or positive design of the material was presented to the participants on the computer. Participants were told that they would be tested on the content of the material after using the computer program and were instructed to study the learning material for 15 min. Participants were then given 25 min to complete the questionnaires of mental effort and perceived task difficulty, the PAS for the second time (PAS2), and self-report measure of intrinsic motivation, learning performance (comprehension and transfer tests), perception of achievement, and satisfaction with their learning experience.
3.3. Results
Table 1 shows the descriptive statistics for the independent and dependent variables involved in the analyses.
3.3.1. Manipulation check of mood induction
3.3.1.1. Evidence of positive mood induction. In order to test whether the mood induction was successful, we computed an independent samples t-test on the scores of the first PAS test by mood induction condition (neutral, positive). The analysis revealed that after the mood induction, the Positive Emotion (PEND and PEPD) groups (M ¼ 22.61; SD ¼ 4.88) rated their emotions significantly more positively than the Neutral Emotion (NEND and NEPD) groups (M ¼ 19.28; SD ¼ 5.03) at t(119) ¼ 3.69, p < .001, Cohen’s d ¼ .68. These results suggest that the neutral versus positive emotional states were successfully induced before the learning session.