When will people understand that comfort is a state of the mind?

Tons of books, classes and articles introduce the topic of comfort by stating that "comfort is a state of the mind", "comfort is a perception formulated by the brain", "psychology and physiology are equally important in the determination of a person's level of comfort", "thermal sensation does not really tell you anything about whether people will like it", and so on and so forth. In my opinion, these are quite clear statements; and yet, lots of people are still confused. Why do we need to remind people, again and again, that a temperature between 22C and 25C—or even a neutral thermal sensation—does not necessarily imply comfort? I will argue in this article that we—engineers, building scientists, researchers and academics—are to blame for this confusion because we do not really treat comfort as a state of the mind in practice.

For the sake of clarity, I am going to focus mainly on Thermal comfort (and a bit of daylight) for the rest of this article. It is up to you to extrapolate it to visual or acoustic or other domains of comfort if you want. Also, I will not reference anything here. I will leave that for my PhD dissertation.

Comfort is a state of the mind only in principle

The rational approach to thermal comfort is one of the two main paradigms from which thermal comfort is studied. It is characterized by the fact that it gathers data through laboratory experiments in order to develop equations that can estimate people's thermal sensation based on several thermodynamically-relevant variables (e.g. people's metabolic rate and clothing, air temperature, wind speed, etc.). These models usually assume that people who report a neutral or close-to-neutral thermal sensation (e.g. "I feel neither cold nor hot") are comfortable. This approach does not treat comfort as a state of the mind, and I do not think it ever tried to. It simply tries to predict thermal sensation by assuming that it depends only on thermodynamics and physiology.

Some people argue that the results of models built from laboratory data will be representative of only a handful of real cases. For instance, since the environmental chambers in the labs do not have any openable windows, models of the rational approach are not supposed to work in buildings that rely on natural ventilation. Because of this kind of limitations (and some more), the other approach to thermal comfort—the so-called adaptive approach—has historically gathered data from field studies. The consequence of this difference is of paramount importance: since the data gathered in the field captures people's reactions to different temperatures, models built through the adaptive thermal comfort will incorporate the fact that people actively seek comfort through behavioural, physiological and psychological adaptation. Does this mean that this model fully embraces the idea that comfort is a state of the mind? I would say NO.

The psychological mechanisms through which people adapt to different environments are often hidden in a big black box that researchers are afraid to open as if it was Pandora's one. Consequently, the models built from the adaptive approach intend to predict people's subjective evaluations (usually thermal sensation) from only climatic variables that we can measure. Why would our psychological adaptation be limited to only those aspects of the environment that we can measure? Or even more, why would people's thermal sensation be the main cause of their comfort? Doesn't this sound just like a physiological model?

Evidence suggests that there is much more beyond objective climatic variables and people's thermal sensation. People are known to change their self-reported thermal sensations based on what they know the temperature in the room to be (even if they have been misinformed) or how it is furnished. This implies that non-climatic variables are also important. Likewise, people are more tolerant of otherwise uncomfortable temperatures when they have more control over the environment. This implies that thermal sensation is not the only thing that matters.

These facts, however, are mostly treated like anomalies or curiosities. They seem to have been paid little attention and they have not been appropriately incorporated in any thermal comfort model that I am aware of. Some might say that models built from the adaptive approach might capture the effects of these factors (because the data is gathered from the field) but they are not incorporated as inputs to such models. They are only assumed to be there and put in Pandora's black box.

Thus, despite these curiosities, models from the two main approaches to thermal comfort rely only on physiological and thermodynamical quantities to predict people's thermal comfort. Thus, it is only natural for people to think that "22C is comfortable. Done". Even more, our models often assume that people are comfortable when they report a neutral thermal sensation. It seems to me, then, that comfort is a state of the mind only in principle. In practice, however, it seems to be common to (over)simplify it to a nearly physiological phenomenon.

So, to answer the original question: when will people understand that comfort is a state of the mind? I would say this can only happen after we really embrace the fact that comfort is a state of the mind. Only when we have models that incorporate psychologically relevant factors will we—and other people—understand what the phrase "comfort is a state of the mind" really means.

How can we truly embrace this "state of the mind" thing?

Because of my PhD, I have been asking people to describe a warm home and a home with good daylight. From their descriptions, I have been able to notice how true is that "comfort is a state of the mind" and how simplistic our models of comfort are when compared with their idea of "comfort".

One interesting finding has been that, sometimes, thermal comfort is completely decoupled from people's thermal sensation and even physiology. How can this be? Well, this was clearly explained by two respondents who argued not to be pleased with the environmental conditions of their dwellings (i.e. they were thermally uncomfortable), not because of their own "thermal sensation", but because of their children's one. This situation became even more interesting when they told me that their children did not seem to care at all about the temperature in their houses.

In a similar manner, my respondents suggested that Daylight does not serve many functional purposes in residential settings. That is to say, even if being able to read is a requirement, it is not nearly enough. People enjoy daylight because it makes the house look cleaner, more welcoming, and allows knowing the time of the day and even the weather. Thus, using daylight to replace electric lighting (e.g. offering 300lx in a workplane) is not really useful.

So, I think the key to embracing the fact that comfort is a state of the mind is to actually ask people and actually listen. Letting them talk without fearing the Pandora's box of subjectivity. In fact, I have found that respondents tend to agree on quite a lot. Even if I am allowing them to speak freely and to mention whatever factor they think makes a home be comfortable; I have gathered a relatively short (i.e. manageable) list of elements to consider during the design process. People are people, and they tend to have similar preferences.

Let me finish by saying that I am aware of the issue of usability. Namely, embracing the idea that comfort is a state of the mind will probably imply some of the factors that predict comfort will not be quantifiable. How do we deal with that? For the sake of brevity, I will address this issue in the near future.


Even if the opinions in it are my own, this article would have not been possible without the guidance of my supervisors Micael-Lee Johnstone, Michael Donn and Casimir MacGregor.