Theory & Research
What Does Research Say About BLS Speed and Set Length in EMDR?
A research-led summary of bilateral stimulation speed and set length in EMDR: what experimental studies show, what clinical protocols describe and why no single setting is universal.
BilateralSync · Updated · 9 min read
Overview
Therapists often ask how fast bilateral stimulation should be and how long a set should last. The honest answer is that research gives useful direction but no single speed or set length has been shown to be universally correct. Experimental studies point towards stimulation that is demanding enough to tax working memory; clinical protocol texts describe starting points that the clinician adjusts to the client.
What the evidence says
Speed — experimental findings. Maxfield, Melnyk and Hayman (2008) found that fast eye movements reduced the vividness and emotionality of recalled memories more than slow eye movements, consistent with a working-memory account. Van Veen and colleagues (2015) reported that the effect of eye-movement speed depended on the individual: speeds that taxed a person's working memory more were associated with greater reductions in memory vividness.
Why this matters. The working-memory theory (Gunter & Bodner, 2008; van den Hout & Engelhard, 2012) predicts that the benefit of a dual task depends on how much it competes with the memory for limited working-memory resources. That suggests the "right" speed is partly individual rather than a fixed number.
Limits of the evidence. Most of these studies were laboratory experiments with non-clinical participants recalling unpleasant autobiographical memories, measuring short-term changes in vividness and emotionality. They do not directly test PTSD treatment outcomes, and they do not establish an optimal number of passes or seconds per set for therapy.
In practice
Set length in clinical protocols. Shapiro's protocol text describes a baseline of around 24 back-and-forth movements per set, increased or decreased according to the client's response and signs of ongoing processing (Shapiro, 2018). This is a protocol starting point, not an experimentally optimised value.
What is a clinical decision. The clinician watches the client and adjusts: shortening sets if the client is overwhelmed or losing dual attention, lengthening them if processing is clearly continuing. Speed may be increased if the stimulus is too easy to follow, or reduced if the client cannot track it.
Summary: what research does and does not tell us
| Question | Status |
|---|---|
| Do eye movements during recall reduce vividness and emotionality? | Supported by many experiments and a meta-analysis (Lee & Cuijpers, 2013) |
| Are faster movements more effective than slow ones? | Supported by some research (Maxfield et al., 2008), with individual differences (van Veen et al., 2015) |
| Is there one optimal BPM or speed for everyone? | Not established |
| Is there an optimal number of passes per set? | Not established; protocols give starting points |
| How should speed be chosen in a session? | Clinical decision, guided by client response |
Why there may not be one universal setting
Working-memory capacity differs between people and changes with arousal, fatigue and the material being processed. A speed that fully engages one client may be trivial or impossible for another. Stimulation modality also matters: visual, auditory and tactile stimulation tax working memory to different degrees (see visual vs. auditory vs. tactile BLS).
Practical implications for tools
A BLS tool should let the therapist change speed and stop or start a set instantly, rather than locking in one preset. In BilateralSync speed, pattern and sound are adjusted live from the therapist's screen; the tool does not decide set length. Background on mechanisms is in how bilateral stimulation works and the bilateral stimulation overview; more studies are listed in the research library.
Frequently asked questions
- How long is an EMDR set?
- Protocol texts describe a starting point of around 24 back-and-forth movements, adjusted to the client. Research has not established a single optimal set length.
- What is the best speed for bilateral stimulation?
- Experimental studies suggest faster, more demanding eye movements reduce memory vividness more than slow ones, but the effect varies between individuals. No universal speed has been established.
- Should speed change during a session?
- That is a clinical decision. Many clinicians adjust speed to keep the stimulus engaging but trackable for the individual client.
References
- Maxfield, L., Melnyk, W. T., & Hayman, C. A. G. (2008). A working memory explanation for the effects of eye movements in EMDR. Journal of EMDR Practice and Research, 2(4), 247–261.
- van Veen, S. C., van Schie, K., Wijngaards-de Meij, L. D. N. V., Littel, M., Engelhard, I. M., & van den Hout, M. A. (2015). Speed matters: Relationship between speed of eye movements and modification of aversive autobiographical memories. Frontiers in Psychiatry, 6, 45.
- Gunter, R. W., & Bodner, G. E. (2008). How eye movements affect unpleasant memories: Support for a working-memory account. Behaviour Research and Therapy, 46(8), 913–931.
- van den Hout, M. A., & Engelhard, I. M. (2012). How does EMDR work? Journal of Experimental Psychopathology, 3(5), 724–738.
- Lee, C. W., & Cuijpers, P. (2013). A meta-analysis of the contribution of eye movements in processing emotional memories. Journal of Behavior Therapy and Experimental Psychiatry, 44(2), 231–239.
- Shapiro, F. (2018). Eye Movement Desensitization and Reprocessing (EMDR) Therapy, 3rd ed. Guilford Press.
This article is general professional information for clinicians. It is not clinical advice and does not replace EMDR training, consultation or individual clinical judgment. BilateralSync is a tool for delivering bilateral stimulation; it is not a treatment or a medical device.