Technology: general issues 8 History of engineering and technology 7 Classification (of information) 3 Computer science 3 Gray wolves 3 Optimizers 3 grey wolf optimizer 3 Behavioral research 2 Bi-directional 2 Bi-directional long short-term memory 2 Binary gray wolf optimizer 2 Biomedical signal processing 2 Brain 2 Brain computer interface 2 Electroencephalography 2 Electrophysiology 2 Emotion recognition 2 Feature extraction 2 Human communications 2 Information technology industries 2 Interface states 2 Learning-based approach 2 Long short-term memory 2 Performance 2 Recognition models 2 Speech recognition 2 bi-directional long short-term memory 2 binary grey wolf optimizer 2 brain–computer interface 2 classification 2