I. Introduction
Emotion strongly influences in our daily activities, such as interactions between people, decision making, learning, and working. Picard developed the concept of affective computing, which aims to be used to study and develop systems and devices that can recognize, interpret, process, and simulate human affects [1]. Human emotion recognition is a current hotspot in affective computing research, and it is critical for applications, such as affective brain–computer interface [2], emotion regulation, and the diagnosis of emotion-related diseases [3].