Mirror-touch synesthesia is a rare condition which causes individuals to experience a similar sensation in the same part or opposite part of the body (such as touch) that another person feels. For example, if someone with this condition were to observe someone touching their cheek, they would feel the same sensation on their own cheek. Synesthesia, in general, is described as a condition in which a concept or sensation causes an individual to experience an additional sensation or concept. Synesthesia is usually a developmental condition; however, recent research has shown that mirror touch synesthesia can be acquired after sensory loss following amputation. The severity of the condition varies from person to person. Some individuals have intense physical synesthetic responses to any physical touch they see, while others describe their experiences as feeling an "echo" of the touch that they see. This appears to be comparable to the projective versus associative distinctions found in other forms of synesthesia. In addition, some mirror-touch synesthetes feel the phenomenon only in response to other humans being touched, while others also perceive it when animals or even inanimate objects are being touched. Mirror-touch synesthesia is found in approximately 1.6–2.5% of the general population. Mirror-touch synesthesia may also co-occur with autism. Some research suggests that mirror-touch synesthetes have higher levels of affective and pain empathy than those without the condition, though cognitive empathy differs from person to person. Their emotional experience of the observed touch may differ from the emotional experience of the person being touched—somebody may perceive a pleasant touch as unpleasant or vice versa. However, other research fails to find evidence of heightened empathy in mirror-touch synesthetes.
Introduction Three conditions must be met in order to confirm the presence of mirror touch synesthesia.
The synesthetic response, which is defined as the sensation synesthetes feel after observing someone else being touched, should feel like conscious experiences. Synesthetic responses have to be induced by a stimulus that normally does not induce that response. The synesthetic experiences must occur automatically, without conscious thought. In order to examine the prevalence of this condition, a study was conducted at the University College London and University of Sussex. 567 undergraduate participants were recruited and given a questionnaire. From the questionnaire, it was determined that approximately 1.5% of the population experienced mirror-touch synesthesia symptoms. Further studies have shown the prevalence to be 1.6%, meaning that this condition is one of the more common types of synesthesia, along with grapheme-color synesthesia (1.4%) and day-color synesthesia (2.8%). At the moment it is believed that there are two subtypes of the condition. The first type causes a person to feel sensations on the part of their body that mirrors the observed touch. The second type causes a person to feel sensations on the same side of their body as the observed touch. Studies have attempted to more explicitly define the intensity of synesthetic responses. In most studies, participants are asked to observe someone else being touched and report what kind of synesthetic response they experience. In one particular instance, video clips were used to show different types of observed touch. The intensity of the synesthetic touch is not affected by the location of the observed touch (arm, leg, hand, etc.); however, it is sometimes affected by the spatial orientation of the observed touch. When crossed hands are touched, the hands become uncrossed in the perception of synesthetes. However, when the observed hand is upside down, the observed touch does not get rotated. Intensity is also not affected if the observed act consists of someone touching themselves, versus someone touching them. Additionally, the type of object doing the touching has a significant effect on the intensity of the response. If a finger or knife tip is used, a much higher intensity is experienced than if a feather is used. Finally, watching a dummy being touched decreases the intensity of the observed touch significantly. For this reason, it is suspected that in order to experience a synesthetic touch, synesthetes must observe somebody who is capable of feeling sensations. Mirror touch responses are not limited to feeling touch. Mirror touch synesthetes have a higher ability to feel empathy than non-synesthetes, and can therefore feel the same emotions that someone else may be observed to feel. Additionally, some individuals experience pain when observing someone else in pain, and this is a condition usually developed from birth. Approximately 30% of the normal population experience some form of this condition and around 16% of amputees report synesthetic pain after an amputation. This condition can either be acquired or developed. In the congenital condition, synesthetes experience pain in the same location as the observed pain; however, in the acquired condition, high intensity pain is felt at the same location as the trauma.
Reported cases The first reported case of mirror touch synesthesia occurred in 2004 in a patient called C. When observing someone else being touched, she would also experience the same touch on her body. Although she had experienced this sensation for her whole life, she did not realize that it was abnormal until reporting it to someone else. She was an otherwise healthy individual. After realizing that her perception was abnormal, she realized that her first cousin, also a female, also has mirror touch synesthesia, suggesting that it could be genetic.
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