This season's first cold wave, always let a person feel particularly cold.
If you've ever wondered if you've been overreacting to the cold weather in early autumn while wearing several layers of clothing, don't give it a second thought. It may not just be your brain, but your body needs time to get used to the cold.
We have a holistic response to winter over time, so if we have a 10-degree weather in February, we feel warm, but if we have a 10-degree weather at this time of year, we feel cold. Said John Castellani, a cold-weather physiologist at the United States Army Research Institute of Environmental Medicine in Massachusetts.
“随着时间的推移，我们对冬天产生了一种整体性的反应，所以，比如说二月里碰到一个10摄氏度的天气，我们会觉得很暖和，但如果每年的这个时候碰到，就会觉得好冷，”马萨诸塞州美国陆军环境医学研究所(the United States Army Research Institute of Environmental Medicine)研究寒冷天气的生理学家约翰·卡斯泰拉尼(John Castellani)说。
Some experts believe the shift in perception is mostly psychological, but others, including Mr. Castellani, think it's not that simple: there is evidence that the body ADAPTS to cold over time.
Here's a quick look at how our response to the cold in autumn differs from spring, and what we already know and what we still have to learn.
We are all delicate snowflakes
As anyone who has ever argued with someone about the temperature of a room knows, people experience temperature differently, sometimes dramatically.
The reasons vary. Studies have found, for example, that larger bodies lose more body heat than smaller ones because they have more surface area. People with thick subcutaneous fat have better body insulation. The old are more cold than the young.
Psychology is also a factor. And the same goes for behavior: humans are adept at avoiding cold environments, which also reduces the effects of cold.
There's an old saying that 'the body is cold, the heart is hot,' said Mike Tipton, a professor of physiology at the University of Portsmouth in England who studies the body's temperature regulation.
“老话说‘身体是冷的，心是热的’，”英国朴茨茅斯大学(University of Portsmouth)研究人体温度调节的生理学教授迈克·蒂普顿(Mike Tipton)说，“我们把自己裹得严严实实，给房子供暖，穿上衣服，我们在周身重现了我们的热带起源。”
How the body reacts
When the temperature drops, sensors on the skin, called temperature sensors, detect the change and send signals to the hypothalamus. The hypothalamus is a small, versatile area of the brain sometimes called the body's thermostat.
To maintain a safe core body temperature, the hypothalamus directs the body to do one of two things. The main response is a process called vasoconstriction: the constriction of blood vessels on the surface of the body, allowing warm blood from the extremities and skin to return to the core. The body also generates heat by shivering.
When the skin feels cold, its first reaction is to protect the body, says castellani.
How does the body adjust
However, these reactions may change over time.
Studies of people around the world have found that people who are regularly exposed to the cold become more resistant to the cold simply by shivering or constricting their blood vessels.
Aboriginal people in Australia, the African desert and the arctic, for example, had significantly fewer physical responses than people who were not exposed to the same cold conditions (deserts tend to drop in temperature at night).
The same was found even in people exposed to the cold in certain ways. For example, fishermen and workers who process fish need to keep their hands in cold water for long periods of time, but studies have found that their hands are warmer in icy water than those of a control group. Similar conditions have been found in slaughterhouse workers who often have to deal with frozen meat.
Castellani says this explains how a person in a cold climate ADAPTS to winter.
We're going to be cold all winter, but basically we're not going to have a lot of skin shrinkage, he said. 'our area is used to it and we feel warmer because our skin is warmer.' That's why people feel colder about the same temperature in October than they do in February.