## 2 Materials and Methods
### Stage 2--Testing in Laboratory Conditions Using EEG and Face Reading (FA)  
Aromatic compounds that have been profiled on the basis of the biometric preferential tests have been subject to further testing under laboratory conditions. The added value of qualitative testing was realistic sample testing of the aromas in question (sampling interaction) as well as the recording of direct implicit and explicit feedback. A total of 48 participants took part in Experiment 2, and the precondition was that they had to be customers of the selected retail company (they buy food most often in that particular store). The sample size was determined based on similar studies. [PERSON] et al. [32] examined the effect of aromas using electroencephalography (EEG) on a sample of 16 respondents in Croatia. The commercial research agency 2 muse Ltd. (Bratislava, Slovakia). monitored the effect of Christmas scents on consumer emotions using a sample of 20 respondents [33]. The European Society for Opinion and Marketing Research (ESOMAR) argues that most consumer neuroscience research agencies use much smaller respondent samples than those used in traditional market research, with 15-30 respondents being sufficient to achieve quality results [34].The research process under laboratory conditions consisted of five parts:  
* Introduction of the instructions to the respondents, completion of consent to biometric and neuroimaging testing, and the processing of personal data in accordance with GDPR regulation and ethical code of sociological surveys;
* Olfactory sensitivity threshold test;
* Input controlled interview in the form of CAPI;
* Tests of selected aromas using consumer neuroscience tools and an aromatising box;
* Final interview in the form of CAPI. The olfactory sensitivity test was conducted in order to create consumer segments with different sensitivity thresholds as part of the experiment. A certified test from the German company Burghart contains three sets of samples (one N-butanol; two phenylethanol), marked red, blue, and green, and are arranged in descending order from 1 to 10. The Emotiv EPOC headset wireless device was used to measure brain activity, consisting of 14 data and 2 reference electrodes distributed in accordance with the international 10-20 electrode distribution system based on both international standards [35] and [PERSON] et al. [36] and was distributed in the following positions: AF3, F7, F3, FC5, T7, P7, O1, O2, P8, T8, FC6, F4, F8, and AF4, as illustrated by Figure 1. The validity of data obtained via mobile electroencephalography (EEG) using the Emotiv EPOC has been verified by several researchers, such as [37; 38; 39], who used this device to examine the emotional state of respondents and who have demonstrated that the device provides the same results as traditional stationary electroencephalographs (EEGs). The Emotiv EPOC wireless kit is capable of detecting the most important functions of brain activity that are commonly used in medical computer processing/brain simulations of a brain--computer interface (BCI). We were monitoring three basic emotional states: excitement, frustration, and emotional involvement. Individual emotions were calculated on the basis of electrical activity recorded through a group of electrodes necessary to calculate the emotion. The EEG channels that were needed to calculate emotional involvement were allocated in positions O1, O2, F3, F4, F7, F8, FC5, and FC6. With gradual regression, the variables for this model were profiled from similar studies [40; 41; 42]. Excitement was calculated using (BetaF3 + BetaF4)/(AlphaF3 + AlphaF4) based on Giraldo and Ramirez [43], which was also used in another study [44]. There are no specific studies focussing frustration and how to deal with its calculation directly on the basis of recorded brain activity through electroencephalography (EEG), but there are several studies [45; 46; 47] that have clarified the role of the prefrontal cortex and the crown lobe in recognising frustration, which gives some form of credibility to our experiment.