Individuals with mirror-touch synesthesia (also known as vision-touch synesthesia) experience the sensations that they observe in others. For instance, if a mirror-touch synesthete saw an individual slap their knee, they would feel the sensation as if they had hit their own knee.
History and Indicators
Synesthesia has been known to exist for the past 300 years and was thought to be quite rare, mainly because people with the condition maintained silence about their experiences when they realized theirs were not typical. However, Blakemore and colleagues recorded the first official report of a single case of mirror-touch synesthesia in 2005. Vision-touch synesthesia is very unique as it is the tactile sensation or feeling that the synesthete is being touched when he or she sees another person being touched in the same manner. There are two variants of vision-touch synesthesia: body-centered reference frame and viewer-centered reference frame. In body-centered reference frame, the sensation of touch may be mirrored by the synesthete. For instance, if the synesthete saw a person being touched on the left side of her face, the synesthete would experience a tactile sensation on the right side of his or her face, hence the name mirror-touch synesthesia. Other synesthetes will feel the touch sensation on the same side of the face as the actual person being touched (using the same example, both will feel the touch on the left side of the face). This type of vision-touch synesthesia is called viewer-centered reference frame.
Prevalence of Vision-Touch Synesthesia
It is estimated that 1.6 percent of people have some sort of vision-touch synesthesia, with the body-centered reference frame (or mirror-touch) being more common. There are a few vision-touch synesthetes who also have the ability to feel touch on their body or hands when they see an object being touched. Testing vision-touch synesthesia for those who have sensations when objects were touched, researchers touched a mannequin or dummy to see if this would induce a response. For some of these synesthetes, seeing a human-related object (like the head or foot) being touched induced fewer or less intense viewer-centered or body-centered reference frame responses. However, in a very few vision-touch synesthetes, seeing a rubber hand being touched had a greater response; in fact these synesthetes actually felt as if their own hand had been replaced by the rubber hand. This is called rubber hand illusion, which can occur even when another person is not touching the rubber/mannequin’s hand. No other body part elicits the same type of illusion. To date, research has observed that only an object that has the form of a human hand is associated with rubber hand illusion.
Theories of Vision-Touch Synesthesia
Currently there are two theories of mirror-touch synesthesia: threshold theory and self-other theory. Threshold theory states that this type of synesthesia is the extreme end-point of normal brain mechanisms, meaning that the somatosensory system has crossed a threshold of awareness of others being touched that the majority of people’s somatosensory systems have not crossed. Self-other theory states that the synesthetes are not able to distinguish self from others, meaning that this atypical self-other representation in the brain is amplified when seeing another person being touched.
Jennifer L. Hellier
See also: Auditory-Tactile Synesthesia; Grapheme-Color Synesthesia; Lexical-Gustatory Synesthesia; Synesthesia
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Heyes, Cecilia, & Caroline Catmur. (2015). A task control theory of mirror-touch synesthesia. Cognitive Neuroscience, 6(2—3), 141—142.
Meier, Beat, Katrin Lunke, & Nicolas Rothen. (2015). How mirror-touch informs theories of synesthesia. Cognitive Neuroscience, 6(2—3), 142—144.
Ward, Jamie, & Michael J. Banissy. (2015). Explaining mirror-touch synesthesia. Cognitive Neuroscience, 6(2—3), 118—133.