Fig 1.
General scheme of the experimental design.
Fig 2.
Representation of the pre-processing sequence of the facial thermal images and the eleven regions of interest (ROIs).
i) ROIs: LF—forehead (left side); RF—forehead (right side); LPO—left periorbital region; RPO—right periorbital region; TN—tip of nose; LR—left cheek; RC—right cheek; LPN—left perinasal region; RPN—right perinasal region; LCh—chin (left side) and RCh—chin (right side).
Table 1.
Means and standard deviations (SD) of SAM performed by 28 children.
Fig 3.
Feature selection maps for each ROI.
Fig 4.
Mean frequency of feature selection per ROIs per subject.
Fig 5.
Performance of the emotion classification.
Fig 6.
Emissivity variation analysis in the selected ROIs, considering the five emotions, taking as reference the baseline (in green) and the ROI pairs (in blue).
The green highlights (below line 0) indicate the significance of emissivity variations in the ROIs triggered by each emotion in relation to the baseline. The blue highlights (above line 0) indicate the significance of emissivity variations occurred between the bilateral ROIs to verify the facial thermal asymmetry. Legend: EM vs BL means Emotion versus Baseline; ns means no significant emissivity variation (p-value > 0.05), while * (p-value ≤ 0.05), ** (p-value ≤ 0.01) and *** (p-value ≤ 0.001) indicate significant emissivity variation.
Fig 7.
Representative frames of the emissivity decrease (in relation to baseline) in nose of a child during the emotions.
Pixel intensity: 0–255.