If you’ve seen someone tapping their knees or shoulders on the subway lately, alternating between tapping their left and right sides, they’re using a science-based technique called “bilateral stimulation” to help calm their nervous system. Bilateral stimulation (BLS) works by engaging the same neural networks that light up when we’re in REM sleep—when our eyes move back and forth even though they’re closed and we’re not consciously aware we’re doing anything at all.

Intentionally doing BLS while we’re awake can help reduce anxiety by activating our parasympathetic nervous system, which is the body’s rest-and-digest mode. In other words, BLS helps our body shift out of being in an activated fight-or-flight response (which by definition happens whenever we’re feeling stressed out), and into a calmer, more present state.