In the debate over whether people should work in the office, or remotely, the in-the-office folks have one good point. A lot of things happen when we interact face-to-face that don’t necessarily happen virtually.

Human beings had little ability to communicate with those who weren’t physically close to them until the past century, and our brains don’t evolve as rapidly as technology. Fortunately, understanding the science of what happens when people interact in person helps us see what’s best done that way, and when virtual meetings are fine. Here’s what’s going on:

Touch Builds Trust

Often, when people meet face-to-face, they touch each other. This can be ritualized (a handshake) or just in the course of holding doors, or a business-appropriate touch on the arm at the end of a meeting. Regardless, touch is a powerful sense. An experiment done by researchers at the University of Chicago and Harvard found that negotiators who shook hands were more open and honest, and reached better outcomes. Shaking hands causes the centers of the brain associated with rewards to activate. You are literally conveying warmth.

Shaking hands causes the centers of the brain associated with rewards to activate.

“That feeling is something so rare, you cannot communicate it digitally,” says René Shimada Siegel, president and founder of High Tech Connect, a consulting firm. “It’s that kinetic energy that people can feel.” Touch builds trust. That’s why job interviews and project pitches generally need to be done in person. People who trust each other work better together, and face-to-face interaction facilitates that. Video conferencing can produce many of the benefits of face-to-face interaction (Siegel estimates it at about 80% as effective), “but it still doesn’t replace someone literally walking in and shaking my hand,” she says.

You Pick Up Hidden Messages

Albert Mehrabian, a major figure in the study of non-verbal communication, introduced an equation about contradictory feedback in his 1971 book Silent Messages: “Total feeling = 7% verbal feeling + 38% vocal feeling + 55% facial feeling.” In other words, “the degree of liking conveyed by the facial expression will dominate and determine the impact of the total message.”

It’s harder to hide reality in person.

A lot of this is done unconsciously. People’s pupils dilate when they are happy or excited, and constrict when they are sad. As you look into someone’s eyes, you absorb this emotional information and respond. This means face-to-face meetings are best when you feel someone is being too guarded, and you’d like to know the truth (e.g., a client isn’t really happy with your team, but doesn’t want to engage with the conversation). It’s harder to hide reality in person.

You Mirror Emotions

Italian neuroscientist Giacomo Rizzolatti (and colleagues) developed the idea of “mirror neurons“—when you see a person take some action, your brain fires up the neurons associated with the same action. When your conversation partner smiles, a part of your brain smiles too.

This emotional contagion shouldn’t be underestimated. If you want to introduce employees to a new program, you can send them an email or schedule a conference call to give them the details. If you want them to be as excited as you are about it, on the other hand, you’re probably better off conveying the excitement in person.

You Pay More Attention

Partly this is just practical: There are social consequences to looking at your phone when someone is talking with you if she can see you do it. But also, as all your senses are engaged in noticing things about the other person, including aspects that wouldn’t be picked up by video conference, that forces your brain to work harder and be more engaged. “A new environment offers the opportunity to introduce novel experiences and situations to wake up our brains and open them to see things from a new perspective,” say Mary Beth McEuen and Christine Duffy in a white paper published by The Center for Hospitality Research at Cornell University (which argued for more investment in business travel). A face-to-face meeting conveys to the other person that the topic, and the person, are important (if only because you sacrificed the time necessary to meet face-to-face).

You Like The Person More

The more we see someone the more we decide we like him or her. The person becomes part of our “tribe.” One new paper on remote work, being published this fall in the Academy of Management Discoveries, found that once the quantity of remote workers in a company reaches a tipping point, people who still work on-site start finding the office sad and dispiriting. A good number of people desire the social interaction of having lots of people around.

All of this can be taken too far, of course. The fact that people enjoy seeing colleagues doesn’t mean everyone needs to be in the office five days a week. Working remotely is often more productive. It’s also a great recruiting and retention tool for people who desire better work/life balance. The best approach might be “core hours” when everyone’s there, with flexibility at other times. That way you can get the advantages of what we know happens during face-to-face interaction—but still get stuff done too.