Why does reading ghost stories make my back cold? It's really cold ... what's the whole principle?

The brain has the function of self-protection and will produce various reactions after being stimulated by the outside world. When you meet happy things, your heart will speed up and your body will get hot; When you encounter fear, your blood vessels will contract. The reason why you will get cold in your back when you read ghost stories is because fear causes blood vessels to contract, body temperature to drop, and your back is less fat and sensitive to temperature, so you will feel cold in your back.