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

The measurement of eye movements is essential for many visual experiments. Eye movements are determined using eye tracking technologies, which usually also measure the pupil diameter in combination.

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.

Other procedures

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.