Condescending smiles are – much like elevator farts – unnecessary, and painful for all who witness their emergence. You can’t be blamed for feeling veritably murderous when one is fired your way.

Fortunately, as science has no boundaries, a team led by the University of Wisconsin-Madison’s Department of Psychology decided to find out how our bodies react to different types of smiles, including those imperious grins. Spoiler alert: It turns out – unsurprisingly – that these unwelcome grimaces really do stress us out, much in the same way negative verbal cues do.

Smiles, in whatever form they come, are just one small facet of our complex repertoire of body language, and non-verbal communication is just as important as anything we actually say. What we hear and what we see in terms of other people affects our perception of them, and the team’s Scientific Reports study points out that our analysis of this interaction is, to some degree, wanting.

If we engage in public speaking, for example, or even if we’re merely about to, our body reacts – we get sweaty palms, an increased heart rate, and so on. This is driven by our hypothalamic-pituitary-adrenal (HPA) axis, a network of feedback interactions that regulates, among other things, stress, partly using the hormone cortisol.

The HPA’s response to verbal cues is somewhat known, but, the team wondered, “does the HPA axis respond to purely nonverbal feedback, such as facial expression?” In order to answer that, they chose to focus on smiles.

The team recruited 90 men to give a short speech to the camera, whereupon they’d be shown the non-verbal reaction of a judge. Unbeknownst to them, this reaction was pre-recorded; this ensured that the involuntary physiological responses of the participants, upon receiving their judgements, were genuine.

As noted by Science Magazine, there are three types of smiles: encouraging “rewarding” smiles, relatable “affiliation” smiles, and superiority-signaling “dominance” smiles, the final category of which includes those condescending grins. The judge’s response featured one of these three smiles, and, based on the hormonal changes the men experienced, triggered a different response.

In every single situation, cortisol – and stress hormone – rose, but it spiked three-fold when a dominant smile was used. In fact, the “increases in heart rate and salivary cortisol… mirror the influences of negative verbal feedback.”

Essentially, our brain recognizes patronizing smiles as a threat even without any accompanying words, and it responds accordingly.

The limits of this study are recognized by the authors themselves: There was no “neutral” feedback response akin to a control, it’s a small sample size, and men alone were used. Men and women may respond to the same type of smile in different ways – but who’s betting against everyone hating those supercilious smirks?