Evelyn Huynh

Ever wonder why the urge to scratch an itch is strong when another person scratches? Scientists have recently found out why through an experiment. It’s really not a choice nor a psychological response. It is hardwired into the brain.

Yawning, scratching, and other “socially contagious” behaviors have puzzled scientists for quite a while. But now, they have found out why.  

Researchers have concluded in a study on mice that the mere act of seeing another mouse scratch prompts the brain to release a chemical that helps to communicate an itch signal to the spinal cord. In the experiment, a mouse was played a video of another mouse scratching. The part of the mouse’s brain called the suprachiasmatic nucleus was particularly active when it saw the other mouse scratching. It was found to release a chemical known as GRP when this happened. Researcher Dr Zhou-Feng Chen, director of the Washington University Centre for the Study of Itch, found that GRP helps transmit itch signals.     

So rather than consciously choosing to scratch or feeling the need to, the response is hardwired into the brain. When it is triggered, itches that the brain would have ignored become much more noticeable.

The same rules apply for other “socially contagious” behaviors. Various theories have been advanced to explain yawning.

Dr Zhou- Feng Chen said that the study showed a physical rather than a mental one behind the reason. He states, “Itching is highly contagious. Sometimes even mentioning itching will make someone scratch. Many people thought it was all in the mind, but our experiments show it is a hardwired behavior and is not a form of empathy.”

So the next time someone scratches, remember that it hardwired into the brain to scratch as well.