I’m living in Paris for the next few months and psyched to have found a Crossfit-style bootcamp so I can keep up with my training. The group is all French, and they have been friendly and welcoming, including me in the customary bise — greeting each other with a kiss on each cheek — each time we meet. Still, they’ve known each other for awhile and my French is not yet up to speed, so the private jokes and slangy conversation often go over my head, and sometimes I find myself feeling distinctly like an outsider and wanting to just remove myself from the situation.

Fortunately, as a neuroscience geek, I know what’s up. We’re wired to want to feel safe with other people and, even if there’s no actual threat to our physical survival, we’re assessing people as “friend” or “foe and still have a “fight or flight” reaction if we feel like we’re being excluded from the group. One startup CEO, whose company has grown in a matter of months from three co-founders to 40+ people, told me he knows when the team is talking about him because they stop talking when he walks into the room, and he feels hurt and isolated.

And we’re not imagining things when we feel actual hurt at being rejected or left out. Researcher Naomi Eisenberger says that “feeling socially excluded activates some of the same neural regions that are activated in response to physical pain.”

If you work with other people, this is valuable info. The more you understand your instinctive reactions, the more you can temper their effect and avoid triggering “fight or flight” reactions in your team. Keep in mind, says David Rock, founder of the Neuroleadership Institute, the key decision we unconsciously make about everyone we meet is: “Are you in my ‘in’ group or my ‘out’ group?’” If your company is adding new staff quickly and/or operating in different countries, you may unintentionally be creating ‘out’ groups, whether through actual language differences, internal acronyms or distinctions for “early” employees.

Establishing shared goals can be an effective way to turn an “out” group into a strong “in” group — I experienced this in the bootcamp when we broke up into groups of three with a certain number of reps to complete. So can creating a culture of inclusivity. Amir Salihefendic, founder and CEO of the to-do list app Todoist says: “The fact that we work from all over the world has bred a team culture that respects diversity and values new perspectives. Every day I see how that culture is driving innovation and growth in markets that other companies our size just aren’t prioritizing.”