Biosignals are understood as the measurable parameter of the human body over time. Various non-invasive methods are available for research:
Measurement of electrical activity
Many organs produce electrical activities which allow conclusions about the current physical condition. These include
Brain: the electrical activity of the brain is the measured as EEG.
Heart: ECG measures the electrical activity of the heart, from this can be determined the heart rate.
Muscles: by EMG the electrical activity of muscles may be determined, especially the facial muscles play a role for determine facial expressions.
Measurement of eye movements and pupils
Optical measurement methods
Using infrared spectroscopy the oxygen saturation of the blood can be determined optically. From this, in particular, conclusions about brain activities are possible.
In many experiments, it is usual to trace test persons with the help of cameras over time. Special procedures can be used to extract facial expressions and thus the current emotional state of the subject.