Why Do We Forget? The Science of Forgetting

We forget because the brain is designed to prioritise useful information rather than store everything perfectly. Rather than acting like a video recorder, memory is constantly updating strengthening important information while allowing less useful memories to weaken over time. In many cases, forgetting is not a flaw but a feature that helps us learn, adapt and make room for new experiences.

If you’re looking to improve your memory, understanding why we forget is the first step. You may also find our guide to How to Improve Memory: 8 Science-Backed Ways to Remember More helpful.

Why We Forget: Key Takeaways

Memory Is a Process, Not a Storage Device.
New memories can interfere with older ones.
Remembering one thing can make related memories harder to recall.
The brain may actively remove weak or outdated memories.
Occasional forgetting is a normal part of healthy memory and ageing.

Memory Is a Process, Not a Storage Device

Before information can be remembered, it must first be encoded, stored and retrieved. If you’re distracted, stressed or not paying attention, the information may never be properly encoded in the first place, making it much easier to forget later.

This is why attention plays such an important role in memory formation. Improving focus can often improve memory performance, which is why we recommend reading How to Find Focus with a Busy Mind alongside our memory guides.

New Memories Can Interfere with Old Ones

In his review The Psychology and Neuroscience of Forgetting, cognitive psychologist John T. Wixted explains that forgetting is not caused by a single mechanism. Instead, memories may become difficult to retrieve because new information interferes with older memories, because they were never fully consolidated, or because retrieval simply fails when we need the information.

This helps explain why recently learned information is often forgotten more easily than memories that have been repeatedly recalled over time.

Remembering Can Actually Cause Forgetting

One of the most surprising discoveries in memory research is that remembering itself can cause forgetting.

In their landmark study, Michael Anderson, Robert Bjork and Elizabeth Bjork demonstrated that recalling one memory strengthens it while suppressing related memories competing for attention—a phenomenon known as retrieval-induced forgetting.

As they famously concluded:

“The act of remembering can cause forgetting.”

Brain imaging research by Wimber et al. later supported this theory by showing that repeatedly retrieving one memory can weaken the neural representation of competing memories in the brain.

Forgetting May Be an Active Biological Process

Scientists now believe forgetting is not simply memories fading over time.

In their review Decay Happens: The Role of Active Forgetting in Memory, Oliver Hardt, Karim Nader and Lynn Nadel argue that the brain actively removes weak, outdated or irrelevant information. This process may help improve learning efficiency by preventing our memory systems from becoming overloaded.

Supporting this idea, Berry et al. discovered that dopamine signalling promotes forgetting in fruit flies (Drosophila), suggesting that dedicated biological mechanisms exist to remove unnecessary memories. Although these findings cannot yet be directly applied to humans, they provide compelling evidence that forgetting is an active process rather than simply passive decay.

Forgetting Is Usually Normal

Forgetting doesn’t necessarily mean something is wrong.

Researchers at Durham University explain that memory depends on successfully encoding, storing and retrieving information. Distraction, stress, fatigue and competing memories can interrupt this process, making occasional forgetting completely normal.

The Mayo Clinic also notes that forgetting names, misplacing keys or relying on reminder lists becomes more common with age and is usually not a cause for concern.

Memory loss becomes more concerning when it begins interfering with everyday life—for example:

Repeatedly asking the same questions.
Getting lost in familiar places.
Struggling with familiar tasks.
Frequently placing objects in unusual locations.

It’s also important to remember that memory problems are not always caused by dementia. Stress, anxiety, depression, sleep apnoea, vitamin B12 deficiency, thyroid disorders, medication side effects and alcohol misuse can all affect memory and are often treatable.

Can You Improve Your Memory?

Although forgetting is a natural part of how the brain works, memory can often be strengthened through healthy habits and effective learning techniques.

You might also enjoy these related guides:

Conclusion

Ultimately, we forget because memory is selective, competitive and adaptive. Rather than being a flaw, forgetting allows the brain to prioritise important information, remove what is no longer useful and remain flexible enough to continue learning throughout life.

References

Wixted, J. T. (2004). The Psychology and Neuroscience of Forgetting. Annual Review of Psychology, 55, 235–269.
https://doi.org/10.1146/annurev.psych.55.090902.141555
Anderson, M. C., Bjork, R. A., & Bjork, E. L. (1994). Remembering Can Cause Forgetting: Retrieval Dynamics in Long-Term Memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20(5), 1063–1087.
https://doi.org/10.1037/0278-7393.20.5.1063
Wimber, M., Alink, A., Charest, I., Kriegeskorte, N., & Anderson, M. C. (2015). Retrieval Induces Adaptive Forgetting of Competing Memories via Cortical Pattern Suppression. Nature Neuroscience, 18, 582–589.
https://doi.org/10.1038/nn.3973
Hardt, O., Nader, K., & Nadel, L. (2013). Decay Happens: The Role of Active Forgetting in Memory. Trends in Cognitive Sciences, 17(3), 111–120.
https://doi.org/10.1016/j.tics.2013.01.001
Berry, J. A., Cervantes-Sandoval, I., Nicholas, E. P., & Davis, R. L. (2012). Dopamine Is Required for Learning and Forgetting in Drosophila. Neuron, 74(3), 530–542.
https://doi.org/10.1016/j.neuron.2012.04.007
Mayo Clinic Staff. (2024). Memory Loss: When to Seek Help. Mayo Clinic.
https://www.mayoclinic.org/diseases-conditions/alzheimers-disease/in-depth/memory-loss/art-20046326
Moulin, C. J. A. (2024, February). Why Forgetting Is a Normal Function of Memory – and When to Worry. Durham University.
https://www.durham.ac.uk/research/current/thought-leadership/2024/02/why-forgetting-is-a-normal-function-of-memory--and-when-to-worry/