Crossed arms may have originated as a way of physically protecting your body. When we're stressed, we receive comfort by crossing our arms across the torso so we can then reach across and massage our arms with our opposite hands. The arms crossed on chest gesture is universal and is decoded with the same defensive or negative meaning almost everywhere.

The majority of crossed arms positions are motivated by an individual’s desire to shut down and/or shut out. The biggest mistake people make is assuming that all arm crosses are signaling that the person wants to shut you out. In reality, the person may be giving themselves a hug as a way to mollify themselves when many environmental stimuli (like music, lights, passing ambulances, etcetera) are grabbing for their attention at once.

Crossed arms look defensive, and make people appear closed-minded and negative. This is one thing about body language that most people know. However, someone with crossed arms is not necessarily using them as a barrier. Although it may look defensive, people cross their arms for many reasons. They might be cold, there may be no arm rests, or they may simply feel comfortable hugging themselves. It may even be a habit. People tend to mirror others. Consequently, if one person in a group crosses his or her arms, others are likely to subconsciously imitate the gesture. However, if you’re trying to sell something to someone who has his or her arms folded, you want to make sure that the person is not being defensive and putting up a barrier to your pitch. You can make them break this position by handing them something to look at.

There are also variations of the crossed arms. A former powerpoint training boss of mine always placed one hand on the negotiating table, and then placed his other hand on top of the first hand. This created a barrier that the people he was dealing with would have to get through if they were to make a sale. Another technique he used when standing was to grasp one arm with his other hand. I have no idea if he did these motions deliberately, but in effect, these were disguised versions of the folded arms, and served the same purpose whenever he was negotiating.

You can be sure that the crossed arms are a barrier if you can detect muscle tension in the person’s fingers. If, for instance, someone is squeezing their upper arms, it’s a sign that they are suffering from tension or stress.