The big idea: how keeping warm wards off loneliness

As winter approaches, warm-blooded animals have two ways to cope with the cold. The first is anatomical, building a layer of fat under the skin and shedding their svelte summer coat for a snug winter pelt.

The second is social: they can huddle. From mice, voles and rabbits to Himalayan marmots and Barbary macaques, individuals in a group will gather together so that they can share the heat radiating from their bodies and avoid the risk of dying from exposure.

According to a new theory of social thermoregulation, humans have a similar instinct. Brain scans show that the regions associated with temperature control and social behaviour are intimately connected and each can influence the other. When we are physically cold, we feel loneliness more keenly and yearn to be physically and emotionally close to others. Conversely, when we feel emotionally excluded, we start to feel that the temperature has dropped and seek warmth to comfort our bruised egos.

Like those other mammals, this may be hard-wired in our brains through evolution. While humans may not physically huddle, our ancestors would have been reliant on the support of others for food, fuel and shelter – and this would have been especially important when it was cold. The result? We may be especially sensitive to others when the temperature drops, and we are likely to seek out other sources of warmth if we feel that we can no longer rely on the group for support.

The extra chill in our houses may make us more sensitive to exclusion and rejection

This new way of viewing human behaviour emerged in the late noughties. Until then, many scientists had assumed that the connection between temperature and social emotion was purely metaphorical. When we feel close to someone, we celebrate their “warmth”, and when we are shunned we feel that we have been given the “cold shoulder” or an “icy stare”. But there had been no reason to think that there might be something concrete behind these figures of speech.

Professors Chen-Bo Zhong and Geoffrey Leonardelli at the University of Toronto were among the first to investigate this possibility. In one experiment, the researchers asked participants to recall a time when they felt excluded or included. They were then asked to guess the temperature of the room, and the estimates of those who had remembered a time of rejection were about 3C (5.4F) lower than those of the people who had dwelled on a time of social connection. The thoughts of rejection had made them feel physically colder – as if they really had been “frozen out”.

Zhong and Leonardelli next turned to a video game called Cyberball, which attempts to recreate the kind of social rejection that many of us might have experienced in the playground. The participant is ostensibly placed in a group of three and asked to play virtual catch with two other people, hidden out of sight. In reality, two of the players are controlled by a computer. In the beginning, these computerised players are programmed to throw the ball to the human, but after a while they may begin to shun the participant, so that he or she no longer feels part of the game.

Despite the fleeting nature of the interaction, the majority of participants reported feeling sad and rejected after being excluded by the other players. And this seemed to prime them to look for sources of warmth as comfort. They were more likely to want hot foods like coffee or soup and not cold things, like Coca-Cola.

There is some evidence that feelings of rejection may even change the body’s actual temperature. Prof Hans IJzerman at the Université Grenoble Alpes hooked a thermometer to the fingers of Cyberball players. He found that their skin temperature dropped by around 0.4C (0.72F), while those who felt included saw a slight rise.

Importantly, the link between temperature and social perception goes both ways. Studies show that if you are already cold, and are then asked about your sense of social connection, you are likely to report feeling lonelier than if you had been asked in warmer conditions. As a result, you feel a greater desire to seek out other people. And there is a good reason that people want hot food when they’re feeling rejected: when IJzerman gave participants a cup of tea after they had played Cyberball, they reported feeling less hurt by the social exclusion.

Weather conditions can even change the media that people consume. Studies of movie rentals show that when it’s cold outside, we are disproportionately more likely to watch romance films compared with other genres, which, the researchers propose, may be a way of satisfying an increased desire for social connection.

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Like all psychological findings, these results will need to be replicated in large and diverse sets of participants, but if the social thermoregulation theory holds up, it may have serious implications for our mental health. Anecdotally, patients with depression often report feeling permanently cold, and there’s some experimental evidence that their bodies struggle to adjust to changes in temperature. A greater understanding of these mechanisms might suggest new treatments for this disorder.

More immediately, with the soaring fuel bills and potential blackouts coming down the tracks, we may need to consider the emotional effects of the cold this winter. Besides the obvious physical discomfort, the extra chill in our houses may make us more sensitive to exclusion and rejection, and with small slights taking on a new importance, we may feel particularly needy for affection from loved ones. The emotional effects of the cold could be particularly problematic for people living alone, who may find it harder to heat their houses and become especially conscious of their loneliness as the temperature drops.

Clearly, practical solutions to the fuel crisis must come first, but given the emotional implications, we might also look for ways to connect more with those around us. Like those huddling animals, we could all benefit from exchanging a little more warmth – both physical and social – this winter.

• David Robson is the author of The Expectation Effect: How Your Mindset Can Transform Your Life.

Further reading

Heartwarming: How Our Inner Thermostat Made Us Human by Hans Rocha IJzerman (WW Norton, £19.99)

The Keys to Kindness: How to be Kinder to Yourself, Others and the Planet by Claudia Hammond (Canongate, £14.95)

Loneliness: Human Nature and the Need for Social Connection by John T Cacioppo and William Patrick (WW Norton, £12.99)