# Decoding Humor-Induced Amusement via Facial Expression Analysis: Toward Emotion-Aware Applications
## 4 Discussion
### Behavioral Correlates and Facial Expressions of Humorous Amusement  
We first set out to establish the behavioral and facial expressions changes associated with humorous amusement. We found that the intensity of amusement as assessed by the participants was proportional to their evaluations of arousal and pleasantness across participants. High arousal and pleasantness are associated with positive emotions such as being amused, stimulated, and excited, which correspond to the emotional state of mirth expected from amusement [63; 64; 65]. We also found that participants were faster to rate the videos they considered to be either neutral or very funny, but slower to rate somewhat amusing videos, consistent with the fact that decisions were more difficult for intermediate, less clear-cut, cases of funniness. In addition, the perceived intensity of amusement was significantly correlated over time: the more intense the amusement, the longer it lasted. This last result is consistent with previous studies showing that humor-induced amusement has a lasting effect and could constitute a reliable tool for stimulating subsequent memory formation and boosting learning experiences (see [66] for a review).  
Facial expression dynamics further supported these findings: when participants rated a video as funnier, they tended to smile more during and immediately after the video. However, when analyzed trial-by-trial across participants, the correlation between smiles and funniness was relatively weak, which can be explained by the high variance in expressiveness across individuals. Some participants never smiled, while others smiled on most trials (average proportion of smiles per participant: min = 1.0%; max = 90.1%; mean = 25.4% \(\pm\) 22.9). Such variability may reflect individual differences in humor responsiveness and expressiveness--factors known to vary with traits like age and gender [67; 68; 69; 70]. Additionally, transient emotional states (e.g., recent stress) may have modulated amusement expression during the session. Although we could not directly control for this, we aimed to mitigate its effect by (1) presenting a large number of videos per participant and (2) re-labeling video categories based on each participant's individual funniness ratings. This approach reduces the influence of temporary mood fluctuations and preserves the focus on relative intra-individual variation. To further enhance robustness and ecological validity, all humorous videos were pretested in an online study (n = 205) and categorized via unsupervised clustering based on group-level arousal, pleasantness, and funniness scores, weighted by inter-rater agreement. In the main study, we then reclassified the videosat the individual level using a percentile-based method to ensure that the neutral, funny, and very funny categories were statistically distinct per participant. As such, the results reported here were not driven by the content of specific videos but by participants' idiosyncratic ratings, allowing us to model amusement-related processes while accommodating substantial inter-individual differences.