## 4 Results  
### Equipment for Neurophysiological Signals Collection  
The monitoring of human factors through the use of neurophysiological measurements can only contribute to the enhancement of health and working conditions for users if the equipment employed for the collection of biosignals is ergonomically designed and does not impact the performance of activities. Given its significance in an operational context, this section will offer a comprehensive overview of the devices used in the scientific literature in order to obtain information on the primary human factors under consideration. The primary methodology employed in the studies included in this review is electroencephalography (EEG) (percentage on the total selected studies corresponding to 55% [7; 9; 11; 12; 15; 17; 18; 19; 20; 21; 23]), which, as a representative measure of brain dynamics, namely the central nervous system (CNS), enables the monitoring of psychological states such as the mental workload, trust, and attention. In order to investigate the neural correlates of trust in human-machine interaction, [PERSON] and colleagues [21] used the Cognionics HD72 high-density wireless dry EEG system (Cognionics, Inc., San Diego, CA, USA), collecting data from 46 electrodes positioned according to the international 10-5 System [42]. Despite the large number of electrodes in the specific experiment, the instrumentation did not particularly interfere with the performance of the tasks. However, low- to medium-density recording devices are predominantly used in experimental protocols. [PERSON] and colleagues [17] employed the BrainCap EEG system (Brain Products GmbH, Gilching, Germany), which has 32 integrated electrodes (Ag/AgCl and passive) located at standard positions given by the International 10-20 system. Although these systems can reach up to 256 channels, this configuration represents a compromise between wearability and spatial resolution of brain activity. The majority of studies were carried out with low spatial density devices (percentage on the total number of selected EEG studies corresponding to 64% [7; 11; 12; 15; 19; 20; 23]) in order to ensure minimal invasiveness and compatibility with other acquisition devices. The first example is the BrainWatch device, a portable system with wireless data transfer (Smarting MOBI), intended for online estimation of a user's mental workload during manual assembly tasks. This headphone-shaped device was custom-developed for the specific experimental scenario and was equipped with 11 semidry electrodes [23]. Moreover, the 14-channel Emotiv Epoc+ neuro-headset (Emotiv Inc., San Francisco, CA, USA) was used to provide a baseline measure of cognitive activity in conjunction with an eye-tracking system [15]. [PERSON] and colleagues [11] implemented a simultaneous acquisition of signals, EEG and fNIRS, to obtain the brain's electrical signals and hemodynamic activity, respectively. EEG was recorded using TMSi Mobita wireless data acquisition system with 19 electrodes (Twente Medical Systems International B.V., Oldenzaal, The Netherlands), while an eight-channel system, Artinis Octamon (Artinis Medical Systems BV, Elst, The Netherlands), was adopted for fNIRS. [PERSON] and colleagues [20] opted for the B-Alert X-10 nine-channel EEG device (Advance Brain Monitoring, Carlsbad, CA, USA), with electrode placement according to the 10-20 system. The use of iMotions (iMotions, Inc., Boston, MA, USA) facilitated synchronization with another biosignal, electrodermal activity (EDA), which was recorded using the Shimmer3 GSR+ Unit (Shimmer, Boston, MA, USA). Regarding the autonomic nervous system activity monitoring, the EDA signal provides a measure of the continuous changes in skin conductance in response to sweat secretion by the sweat glands. This is why it is used for the assessment of mental states that are reflected in the activation of the sympathetic nervous system, such as stress [43].