Dual N-Back: Improve Working Memory and White Matter Density

In 2013, I came across the dual n-back brain training game. It has been claimed to improve working memory and, additionally, fluid intelligence. While the fluid intelligence claims did not replicate in subsequent studies, the benefits to working memory and white matter density have been consistently shown.

This game changed how I prepare for cognitively demanding tasks -- and it has had surprising benefits for my mental health.

What Is Dual N-Back?

In the dual n-back game, you are presented with two simultaneous streams of information -- typically a visual stream (a square appearing in different positions on a grid) and an auditory stream (spoken letters). You have to indicate when the current stimulus matches the one from N steps back.

For example, in 2-back, you need to remember what happened 2 steps ago for both visual and auditory streams simultaneously. As you improve, N increases -- 3-back, 4-back, and so on. The challenge adapts to your performance.

The game provides an adaptive challenge to your visual and auditory working memory by having you recall what items were presented previously while processing new ones in real time.

The Science

Working Memory

Working memory is your brain's ability to hold and manipulate information in real time. It is different from long-term memory -- it is the mental workspace where you process information on the fly.

Dual n-back training has been consistently shown to improve working memory capacity. This matters because working memory is a bottleneck for many cognitive tasks -- reading comprehension, problem-solving, mental arithmetic, and complex decision-making all rely on it.

White Matter Density

The brain is full of gray matter and white matter. Gray matter is the neurons where processing happens. White matter is the space between the gray matter where connections are made -- it is the highway between the processing centers.

Research published in NeuroImage showed that dual n-back training produces increased integrity of white matter pathways connecting different brain regions. The training group showed increased fractional anisotropy (FA) -- a measure of white matter integrity -- with effects mostly left-lateralized.

In other words, the game does not just improve your performance on the game itself -- it strengthens the physical connections between brain regions.

Fluid Intelligence

Fluid intelligence is defined as reasoning ability and the ability to generate, transform, and manipulate different types of novel information in real time. Early studies (notably Jaeggi et al., 2008) showed dual n-back improving fluid intelligence, but subsequent replication attempts yielded mixed results. The working memory and white matter benefits, however, have been more consistently supported.

My Experience

GMAT Preparation

My interest in dual n-back was not in gains to "intelligence." When I first evaluated the game in 2013, it was in the context of preparing for the GMAT as a second attempt.

My first attempt in 2012 went badly. I lost focus during the test due to intrusive thoughts, leading to going blank during a reading comprehension section. The root cause was depression, which has cognitive costs like loss of concentration and memory problems.

In standardized tests like the GMAT, working memory is a critical component. Not much long-term memory is tested, but the ability to hold information in your brain while answering questions -- reading a passage, keeping track of the argument structure, evaluating answer choices -- is everything.

I practiced the dual n-back game every night for 20-30 days, 20 minutes each session. I practiced at night when already exhausted, so as not to take up valuable mental resources during the day.

The result: I scored 750 (98th percentile) on my second attempt, up from 640 on the first.

I cannot attribute the improvement solely to dual n-back -- I also studied extensively. But the improvement in sustained attention and working memory during the test itself was noticeable.

The Mental Health Connection

Low white matter integrity is correlated with depression. Taking anti-depressants results in improvements to white matter integrity, and so does aerobic exercise -- and so does dual n-back.

In 2022, I finally started the practice again after years away from it. I noticed several benefits:

• My brain seemed to work better together. Thoughts flowed more coherently.
• Very lucid dreams. An unexpected side effect that many n-back practitioners report.
• Reduced frequency and intensity of depressive episodes.
• Improved concentration during long work sessions.

The game is the ultimate challenge to a depressed or anxious brain. Your brain wants to either ruminate about the past or worry about the future. Dual n-back forces you to be fully present -- there is simply no cognitive capacity left for rumination when you are tracking two streams of information at the 3-back level.

What It Feels Like

I want to be honest: the game is uncomfortable. It is not fun. It really challenges your brain and makes you feel dumber than you are, especially when you first start.

You will fail frequently. You will confuse what happened 2 steps ago with what happened 3 steps ago. You will feel frustrated.

This is the point. The discomfort is the training signal. Just like muscle soreness after a workout, the cognitive strain is what produces adaptation.

How to Practice

Here are my recommendations:

• Duration: 20 minutes per session, 4-5 days per week.
• Timing: I prefer night time when already mentally tired, but find what works for you.
• Duration of practice: Commit to at least 20-30 days to see meaningful results.
• Apps: There are free dual n-back apps available on iOS and Android. Brain Workshop is a popular free desktop option.
• Consistency over intensity: Regular shorter sessions beat occasional marathon sessions.

Who Should Try This

• Students preparing for standardized tests (GMAT, GRE, LSAT, MCAT) where working memory matters.
• Knowledge workers who need sustained focus and attention.
• Anyone dealing with depression or anxiety who wants a complementary cognitive tool (not a replacement for treatment).
• Anyone curious about neuroplasticity and what the brain is capable of with training.

Final Thought

Dual n-back is not a magic pill. It is a challenging, uncomfortable practice that requires consistency. But the evidence for its effects on working memory and white matter integrity is compelling, and my personal experience has reinforced those findings.

If you are willing to sit with 20 minutes of cognitive discomfort a day, you might be surprised by what your brain can do.