For context, the Gottman Institute's research has been building up for decades through studying thousands of couples. The team has, thus, been able to identify many factors, habits, and behaviors that spell trouble for relationships—and one of those factors is negative body language. Their research suggests couples who display a lot of negative body language may be more likely to break up.
"Our partner is automatically and constantly scanning our body language for cues about whether they are safe and loved in the relationship," licensed marriage and family therapist Elizabeth Earnshaw, LMFT, previously explained to mbg. "Couples who have closed-off and threatening body language with each other prime their relationship for conflict."
Body language expert Blanca Cobb, M.S., previously explained that when someone's body tenses up, that's a common "negative" expression, which may be related to stress, discomfort, or anger. "Positive" body language—like relaxing the body or resting comfortably—can indicate happiness and trust.
Negative body language can therefore create a cycle of conflict, where the body language incites conflict, and the conflict incites more negative body language. And overtime, this creates an unsustainable relationship environment.