Table 1:
Summary of multiclass emotion recognition techniques
| References | Years | Research gaps | Methodologies | Outcomes |
|---|---|---|---|---|
| [16] | 2025 | Current methods lack simple, fast use of spatial-temporal features for real-time ED. | SVM, KNN approaches. | Recognition rates of 94.65%, 93.98%, and 75.59%. |
| [17] | 2025 | FER methods lack thermal-based deep models for reliable, lighting-independent, accurate emotion recognition. | EfficientNet, GWO, SVM, KNN, RF, and Gradient Boosting techniques. | Accuracy of 91.42% and 99.48%. |
| [18] | 2025 | CNN-based emotion recognition struggles with imbalanced data and unreliable real-time performance across environments today. | CNN models. | Accuracy of 97%. |
| [19] | 2025 | Existing IER methods ignore progressive emotion perception and lack mechanisms to model emotions. | ViT and DPMN. | Accuracy of 75.35% and 66.84%. |
| [20] | 2024 | Existing methods lack concept-guided attention to accurately identify truly emotion-relevant regions in images. | CMANet model. | Gains an improved solution. |
| [21] | 2023 | Existing IEC methods cannot unify different emotion models or handle complex semantic relationships effectively. | Unified generative framework. | Achieves a better outcome. |
| [22] | 2022 | Existing methods overlook broad contextual features around affective regions, limiting robust emotion representation learning. | GCN, GAT, and RPN models. | Recognition rate of 87.47%, 76.05%, and 76.50%. |
| [23] | 2024 | CNN models still suffer from limited accuracy and lack deeper feature extraction for complex image classification tasks. | CNN techniques. | Accuracy of 62.2%. |

Figure 1:
High-level workflow of the proposed OADL-MCEDC approach. fMRI, functional magnetic-resonance image; OADL-MCEDC, Optimal Attention Deep Learning-based Multi-class Emotion Detection and Classification.

Figure 2:
Architecture of hybrid capsule network. FC, fully connected.
Table 2:
Classifier recognition of OADL-MCEDC method on various epochs
| Class labels | Accury | Precin | Recall | Fmeasure | MCC |
|---|---|---|---|---|---|
| Epoch – 500 for multi-classes (angry, blank, happy, neutral, sad, scrambled) | 94.73 | 81.40 | 88.67 | 84.88 | 81.80 |
| 95.40 | 85.77 | 86.80 | 86.28 | 83.52 | |
| 93.58 | 76.96 | 87.73 | 81.99 | 78.35 | |
| 96.80 | 90.95 | 89.73 | 90.34 | 88.42 | |
| 90.71 | 74.85 | 66.67 | 70.52 | 65.18 | |
| 94.02 | 86.38 | 76.13 | 80.94 | 77.62 | |
| Average | |||||
| 94.21 | 82.72 | 82.62 | 82.49 | 79.15 | |
| Epoch – 1,000 for multi-classes (angry, blank, happy, neutral, sad, scrambled) | 95.82 | 84.69 | 91.47 | 87.95 | 85.52 |
| 97.09 | 90.89 | 91.73 | 91.31 | 89.56 | |
| 95.80 | 84.59 | 91.47 | 87.89 | 85.45 | |
| 97.33 | 92.68 | 91.20 | 91.94 | 90.34 | |
| 93.04 | 81.08 | 76.00 | 78.46 | 74.37 | |
| 95.76 | 91.04 | 82.67 | 86.65 | 84.27 | |
| Average | |||||
| 95.81 | 87.49 | 87.42 | 87.37 | 84.92 | |
| Epoch – 1,500 for multi-classes (angry, blank, happy, neutral, sad, scrambled) | 96.44 | 86.78 | 92.80 | 89.69 | 87.62 |
| 97.38 | 91.69 | 92.67 | 92.18 | 90.60 | |
| 97.29 | 89.55 | 94.80 | 92.10 | 90.52 | |
| 97.84 | 94.42 | 92.53 | 93.47 | 92.18 | |
| 95.11 | 87.32 | 82.67 | 84.93 | 82.06 | |
| 96.64 | 92.72 | 86.67 | 89.59 | 87.67 | |
| Average | |||||
| 96.79 | 90.41 | 90.36 | 90.33 | 88.44 | |
| Epoch – 2,000 for multi-classes (angry, blank, happy, neutral, sad, scrambled) | 96.67 | 88.07 | 92.53 | 90.25 | 88.28 |
| 97.56 | 92.33 | 93.07 | 92.70 | 91.23 | |
| 97.80 | 91.68 | 95.47 | 93.53 | 92.24 | |
| 97.87 | 94.07 | 93.07 | 93.57 | 92.29 | |
| 95.49 | 87.21 | 85.47 | 86.33 | 83.64 | |
| 97.11 | 94.41 | 87.87 | 91.02 | 89.39 | |
| Average | |||||
| 97.08 | 91.30 | 91.24 | 91.23 | 89.51 | |
| Epoch – 2,500 for multi-classes (angry, blank, happy, neutral, sad, scrambled) | 97.51 | 91.00 | 94.40 | 92.67 | 91.19 |
| 98.38 | 94.60 | 95.73 | 95.16 | 94.19 | |
| 98.51 | 93.06 | 98.40 | 95.66 | 94.81 | |
| 98.49 | 96.58 | 94.27 | 95.41 | 94.52 | |
| 97.29 | 93.85 | 89.60 | 91.68 | 90.09 | |
| 98.00 | 95.71 | 92.13 | 93.89 | 92.71 | |
| Average | |||||
| 98.03 | 94.14 | 94.09 | 94.08 | 92.92 | |
| Epoch – 3,000 for multi-classes (angry, blank, happy, neutral, sad, scrambled) | 97.93 | 93.05 | 94.67 | 93.85 | 92.62 |
| 98.62 | 95.62 | 96.13 | 95.88 | 95.05 | |
| 98.62 | 93.99 | 98.00 | 95.95 | 95.15 | |
| 98.73 | 97.14 | 95.20 | 96.16 | 95.41 | |
| 97.84 | 94.54 | 92.40 | 93.46 | 92.18 | |
| 98.24 | 95.77 | 93.60 | 94.67 | 93.63 | |
| Average | |||||
| 98.33 | 95.02 | 95.00 | 95.00 | 94.01 |
Table 3:
Details of dataset
| Emotions | Sample images |
|---|---|
| Angry | 750 |
| Blank | 750 |
| Happy | 750 |
| Neutral | 750 |
| Sad | 750 |
| Scrambled | 750 |
| Total Images | 4,500 |

Figure 3:
Sample images.

Figure 4:
Preprocessed images, feature maps, and GradCAM visualizations.

Figure 5:
Confusion matrices of OADL-MCEDC method (A–F) 500–3,000 epochs. OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification.

Figure 6:
(A–F) Average outcomes of OADL-MCEDC methodology on numerous epochs. OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification.

Figure 7:
Accury curve of OADL-MCEDC approach on 3,000 epoch. OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification.

Figure 8:
Loss curve of OADL-MCEDC methodology on 3,000 epoch. OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification.

Figure 9:
PR curve of OADL-MCEDC approach on 3,000 epochs. OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification; PR, precision-recall.

Figure 10:
ROC curve of OADL-MCEDC system on 3,000 epoch. OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification.
Table 4:
Comparative analysis of OADL-MCEDC methodology with existing approaches
| Approach | Accury | Precin | Recall | Fmeasure |
|---|---|---|---|---|
| 1D CNN | 87.00 | 84.22 | 91.15 | 92.69 |
| SVM | 83.80 | 86.78 | 91.32 | 91.27 |
| XGBoost | 82.00 | 86.60 | 93.34 | 94.09 |
| LDA | 79.00 | 94.74 | 93.09 | 85.75 |
| RF | 91.00 | 83.03 | 84.95 | 93.91 |
| DNN | 87.34 | 85.00 | 92.11 | 93.26 |
| Decision tree | 71.99 | 91.85 | 82.83 | 82.62 |
| OADL-MCEDC | 98.33 | 95.02 | 95.00 | 95.00 |

Figure 11:
Comparative analysis of OADL-MCEDC method (A) accury, (B) precin, (C) recall, and (D) Fmeasure. CNN, convolutional neural network; DNN, deep neural network; OADL-MCEDC, Optimal Attention Deep Learning based Multi-class Emotion Detection and Classification; SVM, support vector machine.