October 6, 2026 Independent knowledge on EMDR and trauma
EMDR & Trauma Ratgeber

Glossary

Bilateral stimulation

Also known as: BLS, eye movements

In short

Bilateral stimulation refers to alternating left-right stimuli – eye movements, taps or tones – used during the processing phase of an EMDR session.

Bilateral stimulation (BLS) is the most visible feature of EMDR. The therapist moves their hand or a light back and forth and the client follows with their eyes while keeping the distressing memory in mind. A single set typically lasts around 20 to 40 seconds.

The exact mechanism is still debated. A well-studied explanation is the working memory hypothesis: holding a memory while performing a second task taxes working memory, so the memory becomes less vivid and less emotionally intense.