If you crave romantic movies, there may be a neurological explanation. Researchers from the Sahlgrenska Academy at the University of Gothenburg, Sweden have been looking at the connection between different types of social touch and their meaning. In the process, they discovered something interesting about what happens in the brain when you see a sensual touch, versus experiencing such a caress first hand.


The skin as a social organ
The research findings, published as Vicarious Responses to Social Touch in Posterior Insular Cortex Are Tuned to Pleasant Caressing Speeds in the Journal of Neuroscience, examine the skin as a social organ, an organ often passed over by researchers in order study the eyes and ears and their more obvious link to human communication. The study focused on dynamic touching, a type of touch characterized by continuous movements over the skin that can be repetitive and are often slow, like caressing or stroking.

In this study, male and female participants were placed in an MRI, and their field of vision was restricted while the blood flow to their brain was monitored. Participants were stroked along their forearm with a delicate brush at speeds of 3 cm/s and 30 cm/s, without being able to see their forearm. So there was no visual stimulus. The forearm was chosen due to the presence of a slow conducting, unmyelinated nerve fiber, the C Tactile afferent. These fibers are only present in hairy portions of skin on humans.


The MRI was tuned to monitor blood flow in the posterior insular cortex (PIC) of the brain, because the insular cortex involved in empathetic situations, processing emotions, and even orgasms. For the participants in the study, this portion of the brain was much more stimulated by the slower 3 cm/s movements than the rapid ones, showing an intimate caress to be more stimulating to that area of the brain that a quick slide across the arm.

Visual stimulation and the brain

In the second part of the study, a most interesting connection was made. While the participants' brains were still being monitored in the MRI, they were shown video of a forearm being stroked at 3 cm/s and 30 cm/s as well. These video clips were shown randomly between each participant's own physical caresses. While watching the clips (an image from the video can be seen here), no lag in blood flow to the posterior insular cortex was observed via MRI when the video showed a caress at a rate of 3 cm/s. This led researchers to suggest that witnessing a sensual touch has practically the same impact on that part of the brain as receiving one. "The aim was to understand how the brain processes information from sensual contact, and it turned out that the brain was activated just as quickly when the volunteers got to watch someone else being caressed as when they were being caressed themselves," says India Morrison, the first author of the paper. "Even when we are only watching sensual skin contact, we can experience its emotional meaning without actually feeling the touch directly."


Your brain and empathy
So, is seeing a sensual event in a romantic movie the same to your brain as experiencing a similar event? It is, at least to your posterior insular cortex. Granted, the participants were not able to "see" the individual producing the skin stimulation, as would often be the norm in social encounters. Seeing the individual would possibly provide increased stimulation, but this was a necessary control for the study. The researchers' presentation of the skin as a social organ and the accompanying visualization results definitely poses an interesting result, especially when considering how we might empathize with people and actions we see.

Images from Research Digest, Psychlopedia, and the journal Brain. Sources cited within the article.