Feel the Science

Monitoring emotional response through activation of Autonomic Nervous System

Autonomic Nervous System “interconnects” all organs of the human body

The term emotion is defined as a subjective and conscious experience of the mind and body. It is characterized primarily by psychophysiological expressions, biological reactions, and mental states such as sweating, rapid breathing and fainting.

Sympathetic and Parasympathetic activation

A person’s Autonomic Nervous System (ANS), is divided into two branches, the sympathetic and the parasympathetic nervous system which in many cases have opposite actions. Sympathetic activation (also referred to as Sympathetic arousal) increases when people experience excitement. It also increases with stressors, whether they are physical, emotional, or cognitive. On the other hand, Parasympathetic activation occurs when a body needs to slow down and relax. It can be stimulated by the consumption of a “hearty” meal or deep breathing. Research has shown that emotional response can be measured from a variety of physiological signals.

How is ANS activation measured?

ANS activation can be measured through Electrodermal (i.e., sweat gland) and Cardiovarcular (i.e., blood circulatory system) variations. These changes are comparable to whether they involve Sympathetic activity, Parasympathetic activity, or in most cases both. For example, the skin is the only organ that is purely innervated by the sympathetic nervous system and is not affected by the parasympathetic activation. Thus, increases in sympathetic activation can be observed by monitoring subtle electrical changes across the surface of the skin.

Electrodermal Response is a strong indicator of emotional state

Electrodermal Response (EDR), which we measure through a Galvanic Skin Response (GSR) sensor, has been proven to be a powerful emotion-related indicator. EDR represents changes in the skin’s electrical properties, i.e. electric impedance, due to a psychologically-induced sweat gland activity upon an external stimulus. In particular, EDR is strictly related to the activity of the eccrine sweat glands (located in the palms of the hands and soles of the feet) and the skin pore size. In a variety of induction contexts, electrodermal reactivity varies analogously to emotional intensity. Responses with the highest rate of arousal elicit in either unpleasant or pleasant situations.

Feel the Heart Rate

In contrast to skin, changes in heart rate (time between two consequent heart beat peaks) occur as a result of both sympathetic and parasympathetic activation. Estimates of the parasympathetic nervous system activation, or vagal tone, can be made by extracting the highest frequency component of the heart’s rate variability. We measure heart rate variability through a Blood Volume Pressure (BVP) sensor.

Feel the Skin Temperature

Skin temperature is indirectly innervated by the sympathetic nervous system. Increased activity in the sympathetic nervous system causes vasoconstriction of the blood vessels near the skin, which results in a drop in the skin temperature. As described by Marieb & Hoehn (2007, Human Anatomy & Physiology journal) higher skin temperature is found during unpleasant emotions compared to pleasant emotions, which indicates less sympathetic nervous system activation in negative feelings. We measure such changes with a Skin Temperature (ST) sensor.

Feel the Movement

Finally, the Inertial Measurement Unit (IMU) helps us measure movement and activity in order to improve Feel’s emotion recognition and prediction. Additionally, Feel takes advantage of the Global Positioning System (GPS) embedded in any smartphone. This results in enriching the process of emotion classification and personalized recommendations with geospatial data.

Feel the Technology

Feel wristband is equipped with 4 bio-sensors