## 2 Related Work  
The information processing theory emphasizes that learning is an internal psychological activity of human beings; learning is a process of acquiring and utilizing knowledge through sensory awareness, attention, identification, conversion, and memory [32]. Attention is one of the crucial factors of learning outcomes. During the learning process, attention facilitates active learning, comprehension, and familiarity. Humans exhibit mental attention when they are engaged in various activities; mental attention exhibits three aspects, namely selectivity, continuance, and transferability [23]. Learning requires the transmission of signals; the first step of learning is to stimulate the sensory nervous system from some external object, leading to the excitement. During the entire process, once the stimulus disappears, the excitement of the sensory nervous system briefly remains and becomes a signal [23; 32]. Therefore, one must continuously focus on the topic to be learned to convert it into effective signals processed by the brain [33]. Previous educational research has mainly examined students' attention through explicit behavioral observation and documentation, but the research data have consistently lacked objectivity. From the viewpoint of attention theory and cognitive neuroscience, the importance of studying brainwave intensity is to link the cognitive science concepts of the level of mental description during information processing to the neuroscience concepts of the anatomical level. After discovering the electric discharge released by the electric eel in the late 19 th century, [PERSON] guessed that the same phenomenon would occur in the human body [34]. Subsequently, he recorded the same radio phenomenon in the human skull. [PERSON] documented and measured the tiny discharge process in the human brain. This was the first time in human history that human brainwaves were recorded, and this process [PERSON] named \"EEG.\" Because of the association between brainwaves and human consciousness, medical and educational applications of brainwaves emerged thereafter. Numerous studies have pointed out the close associations of brainwaves with aspects such as stress, job performance, learning outcomes, and attention [34; 35]. For example, some studies have stressed that athletes' attention is strongly enhanced in certain brainwave states (e.g., archers can effectively improve their performance by concentrating on aiming) [35]. Regarding learning outcomes, some theories have stated that the rhythms of classical music can change the state of brainwaves so that people can focus on learning and work with considerable efficiency [36]. Some scholars have also analyzed and explored the relationship between brainwaves and learning outcomes. After the statistical data of various attributes had been obtained, e-learning materials were recommended according to the user profile [37]. Brainwaves are the differences between high and low potentials of the electronic signals in the human brain and are generally measured by connecting electrodes to the scalp. Because the brain consists of two cerebral hemispheres, the transmitted signals vary; this phenomenon is known as frontal EEG asymmetry [35]. Brainwaves are loosely classified by frequency range into four categories, namely alpha, beta, theta, and delta waves [35]. The alpha wave can be easily detected in a relaxed state, whereas the beta wave tends to be detected in an alert state (e.g., concentrated thinking). By contrast, the theta and delta waves become prominent in states of low consciousness or unconsciousness (e.g., meditation and deep sleep). Because the theta and delta waves are weak, cluttered, and irregular, the present study did not investigate these two types of waves. Regarding the bands of brainwaves, each frequency range exhibits a specific physiological significance. Alpha waves are neural oscillations in the frequency range of approximately 8-13 Hz.