What Is the Working-Memory Theory of EMDR?
Eye Movement Desensitization and Reprocessing (EMDR) involves bringing aspects of a distressing memory to mind while simultaneously performing another task, most commonly following a side-to-side visual stimulus with the eyes.
One of the leading scientific explanations for why this may help is known as the working-memory theory.
The basic idea is relatively simple: our working memory has limited capacity. Holding a vivid memory in mind uses some of that capacity. Making rapid eye movements at the same time also requires attention and working-memory resources. When both tasks are performed together, they compete for those limited resources.
Researchers propose that this competition can make the recalled memory temporarily less vivid and less emotionally intense. When the memory is later recalled, it may continue to be experienced in that changed form.
A substantial body of experimental research supports important parts of this explanation. However, working-memory theory does not explain every aspect of EMDR, and researchers continue to study how these laboratory findings relate to the complete therapeutic process.
What Is Working Memory?
Working memory is the mental system that allows us to briefly hold information in mind while using or manipulating it.
You use working memory in ordinary situations all the time.
For example, if someone tells you a phone number and you mentally repeat it until you can write it down, you are using working memory.
If you calculate a price in your head, follow several spoken directions, or try to remember a sentence while thinking about its meaning, working memory is involved.
The important feature for understanding EMDR is that working memory is limited.
People cannot hold an unlimited amount of detailed information in active awareness while simultaneously performing other demanding mental tasks. When two tasks compete for the same resources, performance on one or both may change.
Researchers studying EMDR have applied this principle to emotional memories.
How Does Working-Memory Theory Apply to EMDR?
During EMDR, a person may bring an image or another aspect of a distressing memory to mind while simultaneously following a moving visual target.
According to working-memory theory, both activities require mental resources.
The memory requires resources to keep it vivid and emotionally present.
The eye movements also require resources because the person has to attend to and track a moving target.
Doing both at once creates what researchers often call a dual task.
The theory proposes that because working-memory capacity is limited, the two tasks compete with each other. The memory therefore becomes more difficult to maintain in its original vivid form.
This may result in the memory becoming:
less vivid;
less emotionally intense; or
somewhat different in the way it is experienced during later recall.
The event itself is not erased. The proposed change is in how the memory is experienced when it is brought to mind.
What Does the Research Show?
Researchers have tested working-memory theory in many laboratory experiments.
A common design is straightforward.
Participants identify an unpleasant autobiographical memory. They recall that memory under different conditions—for example, while making eye movements and while simply holding the memory in mind without performing the additional task.
Researchers then ask participants to rate characteristics such as the memory's vividness and emotional intensity.
Across many studies, recalling an unpleasant memory while simultaneously making eye movements has been associated with greater reductions in vividness and emotional intensity than recalling the memory alone.
A meta-analysis by Lee and Cuijpers examined both clinical EMDR studies and laboratory experiments. It included 15 clinical trials and 11 laboratory trials, involving 849 participants overall.
The researchers found a moderate additional effect for eye movements in clinical EMDR studies and a larger effect in laboratory studies. The strongest difference in the laboratory research involved memory vividness. (PubMed)
These findings are consistent with a central prediction of working-memory theory: adding a competing task during memory recall can change characteristics of the memory.
Why Do Eye Movements Use Working Memory?
Following a moving object with your eyes may seem almost effortless, but it still requires attention.
Researchers have tested this directly using reaction-time experiments.
If two tasks compete for working-memory resources, adding one task can slow performance on another. Researchers can therefore use reaction time as an indirect measure of how much mental capacity a particular task requires.
A series of experiments by van den Hout and colleagues found that eye movements interfered with performance on other tasks, indicating that they were taxing working-memory resources.
The same research found that eye movements reduced the vividness of negative autobiographical memories. (ScienceDirect)
A later experiment comparing several eye conditions also found that moving the eyes taxed working memory more than keeping the eyes fixed. (ScienceDirect)
That provides an important link in the theory.
Eye movements do not merely occur at the same time as memory recall. Experimental evidence indicates that they consume some of the same limited mental resources that may be needed to maintain a vivid memory.
Why Would Working-Memory Competition Make a Memory Less Vivid?
Imagine trying to keep a detailed picture in your mind while simultaneously performing another task that requires sustained attention.
As the second task becomes more demanding, maintaining every detail of the mental image becomes more difficult.
Working-memory theory proposes that something similar occurs with an autobiographical memory.
When a person recalls a distressing image without another task competing for attention, more working-memory capacity is available to maintain that image.
When eye movements are added, some of that capacity is redirected.
The memory may therefore be experienced with less clarity or intensity during processing.
Researchers have found this effect repeatedly in laboratory studies involving unpleasant autobiographical memories.
A systematic review focusing on EMDR from a working-memory perspective found broad agreement in experimental studies that eye movements tax working memory and can reduce the vividness and/or emotional intensity of distressing memories. (EMDR International Association)
This does not mean that working memory simply becomes “full” and permanently removes details from the memory. The proposed process is more subtle.
The theory is concerned with how competing demands during recall may alter the way the memory is subsequently represented and experienced.
Does the Memory Stay Less Vivid?
This is an important question.
If eye movements changed a memory for only a few seconds while a person was performing them, that would be less useful for explaining lasting therapeutic change.
Researchers have therefore examined what happens when memories are recalled later.
Experimental research has found evidence that reductions in vividness and emotional intensity can remain after the eye movements have stopped, although results and the durability of the effects vary among studies.
This is one reason working-memory researchers propose that the memory may be updated when it is recalled and then stored again.
Under this explanation, the person retrieves a distressing memory, experiences it under altered conditions while working memory is being taxed, and later recalls a version that may be less vivid or emotionally intense.
Exactly how this updating occurs—and how directly it explains lasting clinical improvement—is still being studied.
Does a Task Have to Involve Eye Movements?
Working-memory theory makes an interesting prediction: if competition for limited mental resources is important, then eye movements should not be the only task capable of producing an effect.
Researchers have tested this prediction.
Other attention-demanding tasks have also been found to affect emotional memories under experimental conditions.
For example, researchers have compared eye movements with auditory beeps. Van den Hout and colleagues found that both could tax working memory and reduce the vividness of negative memories, but the effects were stronger for eye movements in their experiments. (ScienceDirect)
This finding is useful because it supports the underlying theory.
If eye movements worked because of a completely unique property of moving the eyes, other working-memory tasks would not necessarily be expected to produce similar effects.
If working-memory competition is important, however, other sufficiently demanding tasks may also influence the memory.
For a closer look at the different forms of stimulation that researchers have examined, see Eye Movements, Tapping or Tones: What Has Research Actually Studied?
Does a More Difficult Task Work Better?
Not necessarily.
Working-memory theory predicts that the amount of mental competition matters, but that does not mean making the secondary task as difficult as possible will automatically produce a larger benefit.
The person still needs enough working-memory capacity to bring the target memory to mind.
If the additional task requires almost no attention, it may not compete sufficiently with the memory.
But if it requires too much attention, it may become difficult to maintain the memory at all.
Researchers have therefore proposed that there may be an optimal balance between keeping the memory active and placing competing demands on working memory.
This idea has led to experiments varying the speed and complexity of eye movements and other secondary tasks.
The findings generally support the idea that the amount of working-memory taxation matters, although researchers have not established one universally ideal level of cognitive demand for EMDR.
Why Might Different Memories Need Different Amounts of Competition?
Not all memories are equally vivid.
One person may bring to mind a highly detailed visual image, while another may experience a memory that is less visually clear but strongly connected with sounds, thoughts, emotions, or physical sensations.
Working-memory theory suggests that the characteristics of the memory could influence how much competition is useful.
A very vivid memory may place different demands on working memory than a faint one.
This has led researchers to investigate whether secondary tasks can be adjusted according to the characteristics of the memory being processed.
The broader idea is sometimes called working-memory taxation: the secondary task uses part of the available mental capacity while the memory is being recalled.
The science does not yet provide a simple formula for matching a particular task to every type of memory, but the concept has generated a substantial amount of experimental research.
Does Working-Memory Theory Explain Why Eye Movements Matter?
It provides one of the strongest current explanations.
As discussed in Are Eye Movements Necessary for EMDR to Work?, earlier research produced disagreement about whether eye movements contributed anything beyond the rest of the EMDR procedure.
Later evidence strengthened the case that they do have measurable effects.
The Lee and Cuijpers meta-analysis found that adding eye movements produced a moderate, statistically significant effect in clinical EMDR studies. The effect was larger in laboratory studies, with particularly strong findings for reductions in memory vividness. (PubMed)
Working-memory theory helps explain why.
Eye movements require mental resources. Distressing memory recall also requires mental resources. Performing both tasks simultaneously creates competition.
The finding that other working-memory tasks can sometimes produce similar memory effects adds further support to that explanation.
Does Working-Memory Theory Explain All of EMDR?
No.
This distinction is important.
EMDR is a complete psychological treatment with multiple components. It involves more than recalling a memory while moving the eyes.
The full treatment includes identifying relevant memories, thoughts, emotions, beliefs, and physical sensations; processing what emerges; and reassessing how the memory is experienced.
Working-memory experiments usually isolate a much narrower process.
A typical laboratory study might ask someone to recall an unpleasant memory for a short period while making eye movements and then rate its vividness.
That is useful for testing a mechanism, but it is not equivalent to a complete course of EMDR.
Working-memory theory therefore provides a plausible explanation for an important part of the process—particularly the effect of eye movements and other dual-attention tasks on memory—but it does not necessarily explain every therapeutic change that occurs during EMDR.
What Is the Difference Between Laboratory Evidence and Clinical Evidence?
This is one of the most important limitations to understand.
Laboratory experiments are particularly useful for answering focused questions.
Researchers can carefully control whether participants move their eyes, how quickly they move them, what other tasks they perform, and how vivid or emotional the memory feels afterward.
That allows researchers to test whether working-memory competition produces the predicted effect.
Clinical treatment is more complicated.
People receiving EMDR for Post-Traumatic Stress Disorder (PTSD) or other concerns are not simply completing one brief memory experiment. Treatment involves repeated processing within a larger structured protocol.
A 2023 systematic review focusing on working memory and eye movements noted that experimental studies generally support the idea that eye movements tax working memory and reduce the vividness or emotionality of unpleasant memories.
However, the role of eye movements in clinical trials involving people with PTSD was less conclusive. (EMDR Therapy Quarterly)
This means the laboratory evidence for the basic working-memory effect is stronger than the evidence that working-memory taxation by itself explains the full clinical effectiveness of EMDR.
Are There Other Explanations for How EMDR Works?
Yes.
Working-memory theory is one of several scientific explanations.
Researchers have also investigated:
changes in physiological arousal;
orienting responses;
memory updating and reconsolidation;
changes in attention;
learning processes; and
changes in brain activity and communication among brain networks.
These possibilities do not necessarily contradict working-memory theory.
More than one process could occur during EMDR.
For example, eye movements could compete with memory recall for working-memory resources while other aspects of the treatment affect emotional learning, beliefs, attention, or physiological responses.
For a broader overview of these explanations, see How Does EMDR Work? The Leading Scientific Explanations.
Does Working-Memory Theory Mean EMDR Is Just a Distraction Technique?
No.
Calling it a distraction technique misses an important part of the theory.
The distressing memory remains active during the dual task.
The person is not simply trying to avoid thinking about the memory by paying attention to something else.
The proposed effect depends on holding the memory in mind while simultaneously performing the competing task.
That distinction is central to working-memory theory.
If attention were completely diverted away from the memory, the memory would no longer be actively competing for the same resources.
The theory therefore involves divided attention, not simply distraction.
How Strong Is the Evidence for Working-Memory Theory?
There is substantial experimental support for several of its central predictions.
Research has shown that:
eye movements use working-memory resources;
recalling an unpleasant memory while making eye movements can reduce its vividness and emotional intensity;
other tasks that tax working memory can sometimes produce similar effects; and
differences in the amount of working-memory demand can affect memory outcomes. (ScienceDirect)
A meta-analysis also found measurable additional effects from eye movements in both clinical and laboratory research. (PubMed)
What remains less certain is how completely this mechanism explains the results of full EMDR treatment.
Working-memory theory explains an experimentally observable process particularly well. It does not yet provide a complete account of every psychological and neurological change associated with EMDR.
That distinction allows the evidence to be described accurately without either dismissing the theory or presenting it as settled fact.
What Can We Reasonably Conclude?
Working-memory theory offers a straightforward explanation for an otherwise unusual feature of EMDR.
A distressing memory requires mental resources to remain vivid in awareness. Eye movements also require mental resources. Because working memory has limited capacity, doing both simultaneously creates competition.
Experimental research consistently shows that this type of dual task can make unpleasant memories less vivid and often less emotionally intense. Meta-analytic evidence also indicates that eye movements can add measurable effects beyond memory recall alone. (PubMed)
The evidence therefore provides meaningful support for working-memory theory.
However, the theory is best understood as an explanation for one important process that may occur during EMDR, rather than a complete explanation of the entire treatment.
Researchers are still investigating how working-memory effects relate to lasting symptom improvement and how they interact with other memory, emotional, physiological, and learning processes.
Frequently Asked Questions
What is working memory?
Working memory is the limited mental system used to temporarily hold and work with information. Because its capacity is limited, performing two demanding mental tasks at the same time can cause them to compete for available resources.
How does working memory relate to EMDR?
During EMDR, a person may recall a distressing memory while simultaneously making eye movements. Working-memory theory proposes that these two activities compete for limited mental resources, which can make the memory less vivid and emotionally intense.
Do eye movements really use working memory?
Yes. Experimental studies using reaction-time tasks have found that eye movements place measurable demands on working memory. (ScienceDirect)
Can something other than eye movements tax working memory?
Yes. Researchers have studied auditory, visual, tactile, and cognitive tasks. Some can also influence the vividness or emotional intensity of memories, although they do not necessarily place identical demands on working memory or produce identical effects. (ScienceDirect)
Does working-memory theory completely explain how EMDR works?
No. It has substantial experimental support and provides one of the leading explanations for the effects of eye movements and dual-attention tasks. EMDR is a complete treatment involving multiple processes, and researchers continue to study how working memory fits with other possible mechanisms.
Conclusion
The working-memory theory of Eye Movement Desensitization and Reprocessing is based on a simple principle: our capacity to hold information actively in mind is limited.
When a person recalls a distressing memory while simultaneously making eye movements, both activities require mental resources.
According to the theory, this competition makes it harder to maintain the memory with the same vividness and emotional intensity.
Laboratory studies, experimental research, and meta-analyses provide substantial support for important parts of this explanation.
Eye movements have been shown to tax working memory, and performing them during memory recall can reduce the vividness and emotional intensity of unpleasant memories.
What remains under investigation is how fully this process explains the lasting benefits of complete EMDR treatment.
Working-memory theory therefore provides one of the strongest scientific explanations for what may happen during the dual-attention portion of EMDR, while remaining one part of a larger and still-developing explanation of how the treatment works.
