There is something special about heat and the psychology of the human mind. Because those who feel socially rejected have average cold fingers than anyone else. Tougher sentences are delivered in a cold courtroom than the temperature is comfortable. If you are talking with a cup of hot tea, you will feel more intimate with his or her conversational partner than holding a glass of cold cola. So it continues in the recently published English book Heart touching Hans Rocha Eigerman, a Dutch psychologist working at the University of Grenoble.

The subtitle of IJzerman’s book goes a long way: How our internal thermostat made us human. But in fact the psychiatrist describes – as a true scientist – that we are still not sure how the old tactics of staying warm still affect our behavior. His request is sufficient to take seriously the ancient human tendency to seek warmth as the basic element of human existence.

Ijeserman – via Zoom – from Grenoble says that even in times of our central warmth and warm fleece jackets, people keep in touch with others via e-mail and WhatsApp from behind their desk when it is cold. “You see in it that the old tendencies to control your body temperature together are still very strong.”

Your entire book revolves around the importance of social thermoregulation. What’s this?

IJzerman: “As an individual, you still rely heavily on personal temperature control when it gets cold. Once it was about reducing the cost of personal energy, now we see its remnants in our social behavior. Once you literally sat or lay next to each other. No one slept alone in bed until the nineteenth century. Now this is mainly reflected in strong social engagement.

I do a lot of experimental psychological research with colleagues on the impact of heat on the social behavior and knowledge of everyday human beings. For example, we did a study in which people are given a warm warm or cold cup. With a cold cup in hand, people seem to think more often about their loved one than warm ones: the cold is active, often without us noticing, social relationships. You see that result especially in people who have had good experiences in their relationships with each other in their lives. People with less positive experiences are less likely to think about their social relationships when they are cold.

“Another example: People raise their skin temperature when they see their partner being sad and have a good relationship with each other. Usually the temperature of the mourners decreases, so we assume that there is some kind of automatic joint regulation of the temperature of each other. You unknowingly prepare to warm your partner. We still need to investigate whether it actually leads to behavior: hug or something like that. ”

These are personal adjustments, but are there any major social consequences?

“Of course! People who live in colder climates – say in Sweden – have a more diverse social network than people in warmer regions – and in Spain or Africa you can see the social impact of thermoregulation. The physical core temperature is higher.

So what does that mean? Do people in Benin have a more unilateral social network than Sweden? Especially family, for example?

“Maybe yes: from a variety of different social domains: family, neighbors, friends, work, classmates, you name it. But beware: we find no effect on size. We are working on further study but we do not yet know the mechanism behind that difference. ”

I thought northern people were more personal. Are you now saying that they have a richer social life than the people of warm countries, in order to stay warm?

“It simply came to our notice then. My suspicion is that you need to be open and going out to keep up with the diverse social networks. Because you need to be able to maintain many different relationships at the same time. It doesn’t have to be particularly large for a diverse social network, but maintaining something like this is complicated. I point out another interesting phenomenon. Especially in northern cultures, and in the Netherlands, people often speak ‘Cosnes’, ‘Haig’ in Danish and Norwegian, and ‘Lagom’ in Swedish. Interestingly, the concept emphasizes general social relationships, but has nothing to do with intense or intimate relationships. This is a common way of dealing with many different social relationships. In fact, you should not invest too much in it. ”

What if you could research it in the eighteenth century? If you can resume now you don’t need a house full of people.

“Yes, we need to work harder now to find the results of that social thermoregulation. But it still exists. We often find that when it’s cold outside, people need to communicate more with others by e-mail or telephone.

“Don’t forget that small children have changed little. Until the age of four, children cannot properly control their own temperature, and they depend on their parents for it. If parents are not very responsive, those children will not die immediately, no, but this may lead to lasting consequences in their emotional control and attachment. You now see that mothers’ skin grafting after newborns is more common in hospitals than it was a few decades ago. Pure social thermoregulation. ”

In your book, you see this thermoregulation as a basis for human social tendencies. But don’t we have many needs that lead to social relationships: food and security?

“Yes, I mention that in the book as well. So you can’t say that people who live more from the equator are more social. We are now examining other domains in our questionnaire. Sharing emotions is clearly related to social thermoregulation, as we have already seen. I think it has to do with sharing food and sharing emotions. “What really happens is that having a good network reduces stress because you actually source our concerns to our. You do not always have to be prepared to respond to threats, because someone on your network can overcome it. ”