From Movements to Metrics: Evaluating Explainable AI Methods in Skeleton-Based Human Activity Recognition

The advancement of deep learning in human activity recognition (HAR) using 3D skeleton data is critical for applications in healthcare, security, sports, and human–computer interaction. This paper tackles a well-known gap in the field, which is the lack of testing in the applicability and reliabilit...

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Veröffentlicht in:Sensors (Basel, Switzerland) Jg. 24; H. 6; S. 1940
Hauptverfasser: Pellano, Kimji N., Strümke, Inga, Ihlen, Espen A. F.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Switzerland MDPI AG 18.03.2024
MDPI
Schlagworte:
Accuracy
CAM
Data analysis
Datasets
Decision making
Deep learning
explainable AI
Grad-CAM
Human Activities
human activity recognition
Human mechanics
Humans
Kinematics
Methods
Movement
Musculoskeletal System
Neural networks
Reproducibility of Results
Sensors
Skeleton
skeleton data
skeleton data
explainable AI
Grad-CAM
human activity recognition
CAM
ISSN:1424-8220, 1424-8220
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Zusammenfassung:The advancement of deep learning in human activity recognition (HAR) using 3D skeleton data is critical for applications in healthcare, security, sports, and human–computer interaction. This paper tackles a well-known gap in the field, which is the lack of testing in the applicability and reliability of XAI evaluation metrics in the skeleton-based HAR domain. We have tested established XAI metrics, namely faithfulness and stability on Class Activation Mapping (CAM) and Gradient-weighted Class Activation Mapping (Grad-CAM) to address this problem. This study introduces a perturbation method that produces variations within the error tolerance of motion sensor tracking, ensuring the resultant skeletal data points remain within the plausible output range of human movement as captured by the tracking device. We used the NTU RGB+D 60 dataset and the EfficientGCN architecture for HAR model training and testing. The evaluation involved systematically perturbing the 3D skeleton data by applying controlled displacements at different magnitudes to assess the impact on XAI metric performance across multiple action classes. Our findings reveal that faithfulness may not consistently serve as a reliable metric across all classes for the EfficientGCN model, indicating its limited applicability in certain contexts. In contrast, stability proves to be a more robust metric, showing dependability across different perturbation magnitudes. Additionally, CAM and Grad-CAM yielded almost identical explanations, leading to closely similar metric outcomes. This suggests a need for the exploration of additional metrics and the application of more diverse XAI methods to broaden the understanding and effectiveness of XAI in skeleton-based HAR.
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ISSN:1424-8220
1424-8220
DOI:10.3390/s24061940