Fractal Dimension and Hurst Coefficient Analysis of the Indian Affective Picture Database- Revised

This study conducted a fractal analysis of the Indian Affective Picture Database-Revised with three primary objectives: (i) to compute the fractal dimension and Hurst coefficient for full face and segmented facial zones (eyes, nose, lips) to examine emotional differences, (ii) to evaluate whether the baseline condition (neutral expression) exhibits commonality across expressers in terms of fractal metrics, and (iii) to investigate fractal dimension changes across facial regions and compare them at -45 and +45 degree angles for six basic emotions. Findings revealed that fractal changes in the eye region significantly exceeded those in the nose and lip zones, as well as in the full face, highlighting the eyes as the most unpredictable in expressing basic emotions. Notably, individual differences were evident even in neutral expressions. The analysis indicated that although the intensity of anger expression varied among individuals, the Hurst coefficient consistently remained higher during anger than in neutral expressions. Similarly, this trend was observed for surprise, with one exception. Conversely, emotions such as happiness, sadness, fear, and disgust displayed greater individual variation. In summary, the results suggest that while the expressions of basic emotions manifest distinctly at +45 degrees— particularly for happiness, anger, and disgust—they do not exhibit distinctive characteristics at -45 degrees.