# Review of Studies on User Research Based on EEG and Eye Tracking
## 5 Discussion
### Current Limitations  
On the one hand, the main driving force of EEG and ET technology in the field of user research comes from people's growing needs for products or services; on the other hand, it comes from technological progress that promotes a deeper exploration of the relationship between vision, the human brain, cognition, perception, and behavior (2018). However, there are still limitations in the feasibility of current technology, due to its complexity and sensitivity to environmental conditions. It is crucial to be thoroughly familiar with eye-tracking protocols and equipment for successful data collection. Although portable devices have expanded the range of experimental sites, they are not suitable for outdoor environments with sunlight interference; instead, they are more suitable for indoor environments, which greatly reduces the feasibility of some experiments ([PERSON] et al., 2018).  
Neuroscientific methods are only good for studying stable and relatively common cognitive characteristics. In EEG experiments, the preparation process is relatively cumbersome. Participants need to clean the oil stains from the surfaces of their scalps in advance, and then inject conductive gel or physiological saline between the electrodes and the scalp to enhance conductivity. The preparation time is generally more than 30 min. Since the experimental results need to be averaged, the time required for ERP experiments will be longer. During experiments, due to the susceptibility of brain neural reactions to external interference, procedures need to be conducted in a relatively quiet environment away from electrical, magnetic, light and other signal interference. The participant's limb behavior and personal conditions will also bring difficulties to subsequent data processing [100]. Therefore, most of the experimental materials that have obtained clear results so far involve still images and videos that can make participants stay still. Although emerging wearable brain state monitoring devices have provided possibilities for conducting measurements outside the laboratory in recent years, these devices present varying degrees of discomfort [101]; this, in turn, will also affect the participant's emotions and reduce the credibility of experimental results. Therefore, it is necessary to clarify feasibility in the experimental design to ensure that experimental designs will have a higher feasibility, and effectively avoid repeated experiments and greatly reduce research time costs to improve research efficiency.  
In addition, the accuracy of the device itself is also a major challenge that the scientific research field needs to face. For example, most of the stimuli used in EEG experiments may mainly reach the cortical area, while aesthetic experiences may be related to the participation of subcortical structures. This problem can only be indirectly intervened through transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) [102]. Therefore, the insufficient accuracy of physiological signal acquisition devices is also a major problem that urgently needs to be solved.