Why is watching a fire so relaxing?

What the blood pressure studies found

Almost everyone agrees that sitting by a fire feels calming, but for a long time nobody had measured it. Anthropologist Christopher Dana Lynn of the University of Alabama set out to do that in three studies published in the journal Evolutionary Psychology in 2014, with 226 adults in total. Participants sat in a darkened office wearing noise-cancelling headphones, with their phones off, and watched recordings of a hearth or a campfire on a computer monitor. Their blood pressure was taken with an automatic cuff before and after each condition, and everyone went through every condition in random order.

The first study compared five minutes of a silent fire with five minutes of a blank, switched-off screen. Systolic blood pressure, the top number, fell by an average of 3.2 mmHg during the silent fire, and the drop during the blank screen was smaller and only borderline. The second study added a third condition, the same fire with its natural crackling sound, plus faint nature sounds for the campfire.

The third study, with 60 people, stretched each condition to 15 minutes and replaced the blank screen with an upside-down still photo of the same campfire. This time blood pressure actually rose during the still photo and during the silent fire. During the fire with sound it fell, by 5.9 mmHg systolic and 3.0 mmHg diastolic on average. Lynn's overall conclusion was that fire with sound consistently lowered blood pressure, that the effect grew stronger with longer exposure, and that there was little support for a purely visual effect.

Why the sound mattered more than the flames

The surprise in these studies is that silent flames were not reliably calming. Lynn suggests that any early relaxation from a muted fire may get cancelled out as people grow bored or annoyed, and reports from participants in the second study suggested the silent fire may have been an irritant because the other senses were missing. Without the sound, he writes, attention may drift to noises outside the room or to thinking and planning, which was likely for students tested between classes.

The controls behaved in their own odd ways. The blank screen gave a modest drop, which Lynn thinks may be because it let people turn inward and use their imagination. The upside-down photo gave no relaxation at all, and several participants said they saw faces in it or were bothered by it.

Fire with sound, in Lynn's words, is visually and aurally naturalistic, and it allows a person to become absorbed in the whole scene. He also measured how readily each participant gets absorbed in experiences, using the Tellegen Absorption Scale. The fire with sound produced the largest drop overall, and it did so even among people who scored lower on absorption, which suggests the combination of sight and sound does some of the work for people who do not easily drift off on their own.

Firelight also changes how people talk

A second line of research looks at what fire does to company. Anthropologist Polly Wiessner of the University of Utah compared 174 conversations among the Ju/'hoan (!Kung) Bushmen of northwest Botswana, recorded in 1974, each involving at least five adults and lasting more than 20 to 30 minutes. Her findings were published in the Proceedings of the National Academy of Sciences in 2014.

By day, 31 percent of the talk was about economic matters such as foraging and hunting plans, 34 percent was complaint or criticism, and 16 percent was joking. After dark, when people gathered around a fire, the mood changed. Wiessner writes that the harsher mood of the day mellowed, and 81 percent of long conversations involving many people were devoted to stories, mostly about people everyone knew.

Lynn's participants were largely alone, and he notes that fireside relaxation may be stronger in social settings, a question he says future research should test. Taken together, the two lines of work suggest that a fire is relaxing partly because of what it does to the senses and partly because of the kind of time it creates: slower, less about tasks, and often shared.

What the research does not show

These are small studies with a narrow group of people. Most participants were college students, and most were women: 51 of 64 recruits in the first study and 53 of 60 in the third. All of them watched recordings on a computer monitor during the day, and nobody in these studies sat next to a real fire.

There is also a quirk that Lynn reports himself. In the second and third studies, blood pressure before the fire-with-sound condition was already higher than before the other conditions, even though the order was randomized. Part of a bigger drop can come from starting higher, and he says so in the paper.

Most importantly, these were short-term readings taken over a few minutes. None of the studies tested whether watching a fire treats high blood pressure, anxiety or any other condition, and a few points of blood pressure during a 15-minute session is not a health treatment.

This article summarizes published research for general interest and is not medical advice. If you have high blood pressure, anxiety or another health concern, talk to a doctor or another qualified health professional.

Common mistakes when you want a fire to help you unwind

Watching with the sound off. In Lynn's studies the silent fire did little and sometimes nothing. The crackle was part of what made the difference, so a muted fireplace video on a television in a noisy room is a different experience from the one that was tested.

Giving it two minutes. The effect grew with longer exposure, and the clearest results came from the 15-minute sessions in the third study. A glance at a fire between tasks is not what was measured.

Doing something else at the same time. Participants turned off their phones and were asked not to do anything else while they watched. Nobody has tested whether a fire playing in the corner of a screen while you scroll has the same effect.

Sitting in the smoke. With a real fire, smoke comes with the light and sound. The US Environmental Protection Agency says wood smoke contains fine particles that can make asthma worse and can trigger heart attacks and strokes in people already at risk, and it lists children, older adults and people with lung or heart disease among those at greater risk.

A fire on a screen is closer to what these studies tested than it might seem, since Lynn's fires were recordings on a monitor. Firepit draws a small campfire on your phone with a layered crackle, and you share it with a few anonymous people who can throw on logs of their own. It makes no claim to lower blood pressure; it is simply a place to sit by a fire for a few minutes.

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