What does BLS stand for?

BLS stands for bilateral stimulation: rhythmic left-right stimulation such as side-to-side eye movements, tones alternating between ears, or taps alternating between the two sides of the body. It is the signature ingredient of EMDR therapy.

Is bilateral stimulation the same thing as EMDR?

No. Bilateral stimulation is one ingredient. EMDR is a structured eight-phase therapy, delivered by a trained clinician, that uses BLS during memory processing. Doing the left-right rhythm on its own is a wellness practice, not therapy.

Does bilateral stimulation work by syncing the brain's hemispheres?

Probably not. The hemisphere-syncing story is popular but has little direct evidence. The best-supported explanation is working memory: recalling a memory while tracking a left-right rhythm splits limited attention, so the memory becomes less vivid and less emotionally intense.

Do tones and taps work as well as eye movements?

Most of the research tested eye movements, so they have the strongest evidence. EMDRIA lists alternating sounds and taps alongside eye movements as forms of BLS; they follow the same left-right logic but have been studied less directly. Pick the channel that feels easiest to stay with.

Bilateral stimulation (BLS): definition and how it works

Q: Can I try bilateral stimulation by myself?

Yes, for everyday stress. Tap your knees in a slow left-right rhythm while holding a mildly stressful scene in mind, and notice whether it softens. For traumatic memories, work with a trained EMDR professional rather than going it alone.

Bilateral stimulation (BLS) is rhythmic, alternating left-right stimulation: side-to-side eye movements, tones that switch between your ears, or taps that alternate between the two sides of your body. It is the signature ingredient of EMDR therapy. Recalling a memory while doing BLS tends to make that memory less vivid and less emotionally intense.

What counts as bilateral stimulation?

In a therapy session, the classic form is visual: your eyes track the therapist’s fingers (or an on-screen target) moving side to side. The EMDR International Association describes this guided back-and-forth as the way EMDR helps the brain reprocess difficult memories, and its walkthrough of EMDR’s eight phases lists two other channels alongside eye movements:

Auditory BLS: tones alternating between your left and right ears through headphones.
Tactile BLS: taps alternating sides, from handheld pulsers or your own hands tapping your knees.

The evidence is strongest for eye movements, which is what the research below tested; tones and taps follow the same left-right logic but have less direct evidence.

How does bilateral stimulation work?

You’ll often read that BLS “syncs the brain’s two hemispheres.” It’s a tidy story with little direct evidence behind it. The best-supported explanation is less mystical: working memory.

Holding a memory in mind takes working memory, and so does tracking a left-right rhythm. Doing both at once splits a limited resource, so the memory loses sharpness and emotional heat, and it tends to stay dimmer afterward. Researchers van den Hout and Engelhard tested this account against competing theories in a 2012 review in the Journal of Experimental Psychopathology and found it held up best.

The evidence is real but bounded. A 2013 meta-analysis of 26 studies in the Journal of Behavior Therapy and Experimental Psychiatry found eye movements added a measurable benefit over recall alone, with the largest effect on how vivid the memory felt.

Is bilateral stimulation the same as EMDR?

No. EMDR is a structured eight-phase therapy that the American Psychological Association conditionally recommends for PTSD; BLS is the ingredient at its center. A left-right rhythm on its own is not therapy, and nobody honest will tell you otherwise.

Can you use bilateral stimulation on your own?

For everyday stress, yes. Try tapping your knees, alternating left-right about once per second, while holding a mildly stressful scene in mind, and notice whether it softens. Our beginner’s guide to self-guided BLS walks through it step by step, and many people use it for everyday anxious feelings.

EmEase, a self-guided EMDR app, is the guided version: visual and audio BLS with adjustable pacing at app.emease.com. If something heavier surfaces, grounding can settle you, and traumatic memories are best processed with a professional — here’s an honest look at doing EMDR on yourself.