If your therapist has recommended EMDR therapy, you might be wondering what bilateral stimulation is and what it will feel like. This guide explains bilateral stimulation in plain language — no clinical jargon, no complicated diagrams.
What is bilateral stimulation?
Bilateral stimulation (BLS) is any form of alternating sensory input — left side, right side, left side, right side. It's a core component of EMDR (Eye Movement Desensitization and Reprocessing) therapy, a well-researched treatment for trauma and other conditions.
There are three main types of bilateral stimulation:
Visual
Your eyes follow a moving object — a dot on a screen, your therapist's finger, or a light bar — back and forth. This is the original form of BLS used in EMDR therapy. It's sometimes called "eye movement" because that's literally what you're doing: moving your eyes from side to side.
Audio
You hear alternating sounds — a tone in your left ear, then your right ear, then left again. This is usually done with headphones. The tones are gentle and rhythmic.
Tactile (haptic)
You feel alternating physical sensations — a tap on your left hand, then your right hand, or vibrations alternating between sides. This can be done with handheld devices, phone vibrations, or wearables like an Apple Watch.
How does bilateral stimulation help?
Researchers believe bilateral stimulation helps the brain process difficult memories and emotions. During EMDR therapy, your therapist guides you through recalling a distressing memory while you receive BLS. The alternating stimulation appears to help your brain reprocess the memory so it becomes less distressing over time.
The exact mechanism is still studied, but the results are well-documented. EMDR therapy is recommended by the World Health Organization, the American Psychological Association, and the U.S. Department of Veterans Affairs for treating PTSD.
It's important to note: bilateral stimulation is one component of EMDR therapy, not a standalone treatment. It works within the structure and guidance your therapist provides.
What does a BLS session feel like?
Here's what you might experience during an EMDR session with bilateral stimulation:
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Your therapist sets up the session. They choose the type of BLS (visual, audio, or tactile), the speed, and the duration. If you're using an app like EMDR Tappers, they might share a link so you can receive BLS on your own device.
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You focus on a target memory. Your therapist guides you to hold a specific memory, image, or feeling in mind.
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The bilateral stimulation begins. You follow the visual movement, listen to the alternating tones, or feel the alternating taps. Most people describe it as calming — a rhythmic, predictable sensation.
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Your therapist checks in. After a set of BLS (usually 20–30 seconds), your therapist pauses and asks what you're noticing. There's no right or wrong answer.
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The process repeats. Your therapist may adjust the BLS type, speed, or target based on your responses. Sessions typically last 60–90 minutes.
Which type of BLS is best?
There's no single "best" type. Research shows that all three types — visual, audio, and tactile — can be effective. Your therapist will recommend the type that fits your situation:
- Visual is the most traditional and widely studied
- Audio works well for clients who find eye movement uncomfortable
- Tactile is popular for telehealth because clients can feel it on their phone or wearable
Many therapists combine types — for example, visual BLS on the screen with haptic taps on an Apple Watch. EMDR Tappers supports all three types simultaneously.
Can I use bilateral stimulation on my own?
Some people use bilateral stimulation for calming exercises, grounding, or resource development outside of therapy sessions. This can include:
- Listening to bilateral audio through headphones
- Using a BLS app for self-guided visual or haptic stimulation
- Following guided bilateral stimulation recordings
Self-guided BLS can be a helpful tool for managing stress and building resilience. However, it's not a substitute for professional EMDR therapy. Processing traumatic memories should always be done with a trained therapist.
If you're interested in self-guided BLS, talk to your therapist about which exercises are appropriate for you.
What devices work for bilateral stimulation?
Modern BLS apps work on the devices you already own:
- Phones and tablets (iOS and Android) — visual animations, audio tones, vibration patterns
- Web browsers (Chrome, Safari, Firefox, Edge) — visual and audio BLS, no download needed
- Apple Watch — haptic taps on your wrist, synced to the session
- Headphones — for bilateral audio tones
With apps like EMDR Tappers, your therapist controls the session from their device, and you receive BLS on yours — even if you're in different locations.
Frequently asked questions
Is bilateral stimulation safe?
Bilateral stimulation as part of EMDR therapy is considered safe and is backed by extensive research. If you experience distress during a session, tell your therapist — they can adjust the stimulation or pause.
How fast should bilateral stimulation be?
Speed varies by individual and therapist preference. Most therapists start at a moderate pace and adjust based on your comfort. There's no single correct speed.
Can bilateral stimulation make things worse?
Processing difficult memories can temporarily bring up strong emotions. This is normal and expected in EMDR therapy. Your therapist is trained to guide you through this safely. Self-guided BLS for calming exercises is generally low-risk, but always follow your therapist's guidance.
How many sessions does EMDR therapy take?
This varies widely depending on the individual and what's being treated. Some people see significant improvement in 6–12 sessions; others may need more. Your therapist can give you a better estimate based on your specific situation.