In order to understand the topic of this article, we must first understand the term synesthesia. Synesthesia is defined as a perception of mixed sensations: stimulating one sense involuntarily causes a person to perceive it with another sense, for example a sound being perceived visually.  Synesthesia is usually a developmental condition, however recent research has shown that mirror touch synesthesia can be acquired after sensory loss following amputation.  There are several types of synesthesia, which have been recognized and studied for quite some times. Others are relatively new to the medical forefront, such as Mirror-Touch Synesthesia (herein referred to as MTS), which was first noted in 2005. Synesthesia are hereditary, passed through the X chromosome (females possess 2 X chromosomes and males 1); likewise, a person who has one type of synesthesia is likely to have other types as well. [1,2,3]
Mirror-Touch Synesthesia is a rare neurological condition in which the “synesthete” (person with synesthesia) physically feels what others experience. One example is that if another person is stroked on their arm, the individual with MTS would feel the sensation of their arm being stroked.  This condition has received attention recently due to a neurologist with the condition, Joel Salinas, MD a neurology resident at Harvard Medical School. Salinas in one noted example, physically felt the sensation of his tapping a patient’s knee to test reflexes, despite the patient showing no clear reflexes. 
One can imagine the difficulty that Dr. Salinas must face every day, being a neurologist and working with people suffering from dystonias (disorders of muscle tone/spasticity), stroke, multiple sclerosis, etc. One early synesthete reportedly witnessed a man being punched and passed out in her car.  MTS for many can be debilitating. Imagine having this condition and witnessing a fatal car accident or murder. Some synesthetes become homebound, even unable to watch television lest they have a physical reaction to what they are watching. Studies show that the intensity of the stimulus does correlate to the intensity of the perceived sensation by the synesthete. For example, a touch vs. a punch.  When Salinas performs a spinal tap on a patient, he can feel the needle going into his own lower back. “When a psychotic patient goes into a rage, Salinas feels himself getting worked up. Even when patients die, Salinas feels an involuntary glimmer of the event firsthand. His body starts to feel vacant—empty, like a limp balloon.” 
MTS “has aroused significant interest among neuroscientists in recent years because it appears to be an extreme form of a basic human trait. In all of us, mirror neurons in the premotor cortex and other areas of the brain activate when we watch someone else’s behaviors and actions. Our brains map the regions of the body where we see someone else caressed, jabbed, or whacked, and they mimic just a shade of that feeling on the same spots on our own bodies. For mirror-touch synesthetes like Salinas, that mental simulacrum is so strong that it crosses a threshold into near-tactile sensation, sometimes indistinguishable from one’s own. Neuroscientists regard the condition as a state of ‘heightened empathic ability.’ “  As you might guess from that quote, those with MTS have responses not only to physical stimulus of others, but also emotions. Studies show that persons with MTS “scored significantly higher…on reading social cues that indicated that a person was feeling confident, stressed, sad, perplexed, or mystified. They’ve also found that mirror-touch synesthetes tend to have a greater volume of gray matter in areas of the brain linked to social cognition and empathy, and less brain volume in the temporoparietal junction, which plays a key role in distinguishing self from other.”  Hence the relevance to National Paranormal Society.
MTS differs from other synesthesia in that it may be genetic in origin, or may develop following a trauma. Some amputees studied perceived stimulus of pain, touch, movement or cold, for example, in limbs which had been amputated. “Phantom pains” are reported by 98% of amputees. [1,2] Personally I recall a relative having excruciating pain in a leg that had been amputated due to complications of diabetes. Stroke patients with paralysis on one side rendered similar results.
Diagnosis of MTS depends on the presence of three criteria: 1) the synesthete’s response upon seeing another being touched must feel like a conscious sensation (i.e. not a delusion or imagination); 2) the responses are induced by a stimulus would not generally cause this response; 3) these sensations must be involuntary, i.e. not by conscious thought.  While quite rare, MTS is among the more prevalent types of synesthesia. It has two sub-types: one, a true mirror touch, where the sensation is felt on the opposite side as that of the person who actually receives the stimulus (as in a reflection), and the other in which the sensation is felt on the same side. 
MTS is a relatively new condition which places scientific research and data in the form of brain-mapping, and the relative mass of certain areas of the brain governing traits collectively assigned to empaths, with neuroscientists describing it as basically a hyper-sensitive form of physical and emotional empathy. MTS is still being studied; however, the results thus far are fascinating.