# Towards Detection of Interest Using Physiological Sensors
## 3 Physiological Patterns and Features of Interest
### EEG and ECG Patterns
Unlike the [PERSON] study, wherein auditory probe stimuli were used, the authors of this study used a somatosensory (vibratory) probe stimulus to account for the masking problem, which may occur when auditory probe stimuli are used. Specifically, it is likely that the auditory probe might be masked when other auditory materials are presented at the same time. After data pre-processing and filtering, ERPs were calculated separately for each participant and condition. The N140 and P300 were then defined and computed, and the peak amplitude and latency were measured (Cz for N140 and Pz for P300). The mean power in the alpha band (8-12.5 Hz) was computed at the Oz site (occipital midline). As expected, the subjective ratings indicated that subjects allocated more attention to the interesting clips and less attention to the probe stimuli. This was not the case for boring clips, which drew less attention. The N140 was significantly smaller in amplitude when the subjects viewed interesting clips when compared to boring clips. As noted by [PERSON] et al. [78], the amplitude of N140 is an indicator of a passive shift in attention. This to some extent explains the change in N140 during the viewing of interesting videos, which captured the subject's attention, when compared to the boring videos or the still images. Interestingly, the P300 amplitude decreased when the subjects viewed interesting videos when compared to boring clips or still pictures. However, the difference was not significant between the two conditions. This suggests that the N140 elicited by vibratory stimuli might be more sensitive in measuring the attention resulting from the viewing of interesting content than the P300. The authors further assessed the effects of interesting content on the alpha band. They found that alpha amplitude was attenuated in the interesting condition when compared to the boring condition or the still picture condition. This finding was in line with the previous findings of [PERSON] et al. [79]. The authors proposed the use of N140 amplitude elicited by vibratory probe stimuli, along with the power of the alpha band recorded from the occipital lobe using EEG, as a useful index of the subject's interest in audio-visual content. [PERSON] et al. [31] used an Emotiv EPOC device with 14 channels. They achieved an accuracy of 73% in the detection of interest, excitement, frustration, and confidence when using EEG and mouse behavior data. In this study, the difference between the raw EEG value and the mean value of the baseline data was normalized and segmented into 2-s bins. Each segment was then treated as a single instance. Mouse data, including number of clicks, distance traveled, and click duration, were used in addition to the EEG data. The EEG data, data on mouse clicks, and self-report data were synchronized and merged. The EEG data and data on mouse clicks were labeled based on the self-report data. Data were then fed to two different classifiers: a support vector machine (SVM) and a multi-layer perceptron. The F-measures were higher when using brainwaves only than when only using mouse data. The F-measure was highest when both modalities were combined. The F-measure reached 73% for the average of all emotions when using the MLP classifier and was lower (51%) when using the SVM classifier. It should be noted that data from 16 out of the 25 subjects were valid for feeding into the classifiers. This is because the number of instances of the occurrence of the four emotions was required to be balanced. Interestingly, the F-measure was improved when the authors used \"outliers\", which were defined as values deviating from the mean by at least one standard deviation. The F-measure reached 92% for the average of all emotions when using the MLP for combined modalities (brainwaves and mouse) data and reached 97% for \"interest.\" According to the authors, interest was likely the most frequently occurring emotion during the learning process in this particular study and was related to the subject's engagement.