The Somatosensory System
The somatosensory system is a part of the brain composed of receptors and processing centers that produce sensory modalities (touch, temperature, proprioception, and nociception – pain). It is mainly located in the postcentral gyrus of the parietal lobe in the brain, and is commonly represented by the cortical homunculus. That’s the funny drawing you see on the bottom right, which roughly proportionately maps the amount of sensation in each part of our bodies to one another.
Embodied Perception Concepts
There are 6 concepts that are helpful to understand when considering embodied interaction:
Kinesthesis
Awareness of the position and movement of the body in space. It is generated through movement
Proprioception
Sensory faculty of being aware of the position of the limbs and internal organs, as well as the strength of effort applied. It is perceived through muscles, joints and tendons.
Interoception
The perception and sensation of our internal organs
Exteroception
The perception of the outside world through external stimuli (visual, auditive, etc.)
Tactile
Refers to the sense of contact mediated by low threshold mechanoreceptors in the fingerpads
Haptic
The perception and manipulation of objects
Mapping the Relationships
The concepts overlap heavily – they inform one another and are inextricably related, making it hard to understand each of their nuances. Having outlined all individually, I constructed the following diagram which describes how all aspects of embodied perception inform one another. This research and diagram is what I shared with my team at Intel Labs, to help them map the relationships of each aspect of perception to our research in wearables:
Haptic and tactile senses are often confused but separate perceptions. Tactile feedback informs the haptic sense, and relies on haptics at a macro level (force applied and position of the body to the object) to inform the sensing of textures through our fingerpads. Kinesthesis includes all skin sensations, proprioception and interoception; it is constantly mediating other forms of sensation (vision, hearing, etc.) to determine the body’s position and movement. Proprioception is heavily intertwined with kinesthesis, since we grow a proprioceptive sense largely by the act of moving our bodies. It’s worth noting that proprioception and exteroception can’t really be separated given that we grow awareness of ourselves both through interoceptive and exteroceptive stimuli. However, all in all the sum of our perceptions help us get a sense of our bodies and in turn, the world around us.