# Usability and Acceptance Analysis of Wearable BCI Devices
## 5 Results  
### State of the Art  
The development of advanced neurofeedback technologies will impact multiple fields of application, from improving neurological and laboratory studies to optimizing the design of real-world environments (e.g., industrial environments and human-machine interaction) [30]. Since brain data are sensitive and could be misused if not handled properly, privacy and security issues arise. Furthermore, technical hurdles such as ensuring accuracy, avoiding signal interference, and improving ease of use often limit smooth integration into applications, especially in the case of specific uses, such as industrial applications, which require adequate and timely training of operators in the use of such devices. In the literature, the EPOCx (Emotiv Inc., San Francisco, California, U.S.A.) device appears to be the most widely used in experiments. Depending on the circumstances, the 14 electrodes that make up the EPOC main unit can adopt anywhere from 10 to 20 predefined settings. Because the electrodes are positioned on semi-rigid plastic arms that are attached to a frame that encircles the head and incorporates a battery/transmitter unit, this system has a limited capacity to adjust and apply to varying head sizes. Overall, the equipment does not provide much room for small or large head sizes; however, the flexible arms holding the electrodes can be adjusted to small distances. In fact, in that case, the electrodes would not contact the scalp or would exert too much pressure. In fact, in this case, the electrodes would not contact the scalp or would exert too much pressure. This causes, in some cases, instability and uneven weight distribution, altering the signal recording and especially preventing the user from moving comfortably during the session. Following a long period of use, the constant pressure could cause discomfort to the subject [30], altering the result of the detection test. In contrast, the B-Alert x10 (Advanced Brain Monitoring, Faraday Ave, Carlsbad, California, U.S.A.) device, despite having the predetermined configuration for electrode positioning, being composed of an overall light plastic structure, ensures less discomfort to pressure. Current research includes the study of anthropometric data as a reference for the design of products in which fit, comfort, functionality, and safety must be optimized. To date, there are mainly two different approaches to the management of anthropometric dimensions and variables: one approach consists of offering headphones in different sizes to fit a wide range of users; another approach consists of offering one size with adjustments, but not always adaptable to all users. From the trial questionnaires, it emerged that the EPOCx device scored worst in terms of comfort, even though it was the one preferred for aesthetics and ease of use [35]. From the point of view of signal quality, EPOCx adopts passive gold-plated electrodes that touch the scalp through felt pads soaked in saline solution, which, however, causes signal obstruction. In addition, coupled with the critical issues concerning the adaptability of the system to the different head conformations of users, it is unable to guarantee continuity of data transmission during use [28]. As [PERSON] & Meffert [35] state, this shows that developers have placed more emphasis on the design of EEG devices than on user-centered design. This can lead to device configurations that are not always user-friendly or comfortable. In these cases, the visual appearance and behavior of the device can influence a person's well-being. Dry or, if necessary, gel-based electrodes, such as those adopted by the Unicorn Hybrid Black (UHB) (g.tec medical engineering GmbH, Schiedlberg, Austria) device, are designed to work efficiently despite direct contact with hair, without requiring any special pressure. In fact, the direct contact between the sensor and the scalp is guaranteed by the presence of conductive rubber electrodes that do not require any other substances to read the signal.