Reasons Why People Forget

4 Key Reasons for Forgetting

A woman writing down something in her daily planner so she doesn't forget.

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While you might find yourself wondering why is my memory so bad, forgetting is part of life. In fact, people forget surprisingly fast. Research has found that approximately 56% of information is forgotten within an hour, 66% after a day, and 75% after six days.

The reality is that while the brain is capable of impressive feats, its capacity to store and recall details is limited. There are a few different ways and reasons that we forget things.

What Does Forgetting Mean?

Forgetting is the loss or change in information that was was previously stored in short-term or long-term memory. It can occur suddenly or it can occur gradually as old memories are lost. While it is usually normal, excessive or unusual forgetting might be a sign of a more serious problem.

This article discusses some of the more common reasons for forgetting. It also explores some other possible factors that can lead to forgetting.

Forgetting Caused by Decay

Have you ever felt like a piece of information has just vanished from your memory? Or maybe you know that it's there, but you just can't seem to find it. The inability to retrieve a memory is one of the most common causes of forgetting.

So why are we often unable to retrieve information from memory? One possible explanation of retrieval failure is known as decay theory.

According to this theory, a memory trace is created every time a new theory is formed. Decay theory suggests that over time, these memory traces begin to fade and disappear. If​ the information is not retrieved and rehearsed, it will eventually be lost.

One problem with this theory, however, is that research has demonstrated that even memories which have not been rehearsed or remembered are remarkably stable in long-term memory.

Research also suggests that the brain actively prunes memories that become unused, a process that is known as active forgetting. As memories accumulate, those that are not retrieved eventually become lost.

Forgetting Caused by Interference

Sometimes people forget due to a phenomenon known as interference. Some memories compete and interfere with other memories. When information is very similar to other information that was previously stored in memory, interference is more likely to occur.

There are two basic types of interference:

  • Proactive interference is when an old memory makes it more difficult or impossible to remember a new memory.
  • Retroactive interference occurs when new information interferes with your ability to remember previously learned information.

Sometimes the act of remembering something can lead to other things being forgotten. Research suggests that retrieving some information from memory can lead to retrieval-induced forgetting. This is particularly common when memory retrieval cues are very similar.

While this causes forgetting, research also suggests that this type of forgetting can actually be adaptive. By forgetting one memory in favor of another, it reduces the chance of interference happening again in the future.

While interference can make it difficult to remember some things, there are things you can do to minimize its effects. Rehearsing new information is often the most effective approach. By essentially overlearning new things, it is less likely that old information will compete with new.

Forgetting Caused by Failure to Store

Sometimes, losing information has less to do with forgetting and more to do with the fact that it never made it into long-term memory in the first place. Encoding failures sometimes prevent information from entering long-term memory.

In one classic experiment, researchers asked participants to identify the correct U.S. penny out of a group of drawings of incorrect pennies. While people are familiar with this everyday object, they were surprisingly bad at being able to detect key details.

The reason for this is that only details necessary for distinguishing pennies from other coins were encoded into your long-term memory. Identifying a penny does not require knowing the exact image or words found on the coin. Because this information is not really needed, most people never memorize it and commit it to memory.

Memories also tend to get simplified. While you might remember the overall gist of something, you are likely to forget many of the details. This is actually an adaptive function that allows you to efficiently store important information that you need to remember in the future.

Motivated Forgetting

Sometimes we may actively work to forget memories, especially those of traumatic or disturbing events or experiences. Painful memories can be upsetting and anxiety-provoking, so there are times we may desire to eliminate them. The two basic forms of motivated forgetting are suppression, which is a conscious form of forgetting, and repression, an unconscious form of forgetting.

However, the concept of repressed memories is not universally accepted by all psychologists. One of the problems with repressed memories is that it is difficult, if not impossible, to scientifically study whether or not a memory has been repressed.

Also note that mental activities such as rehearsal and remembering are important ways of strengthening memory, and memories of painful or traumatic life events are far less likely to be remembered, discussed, or rehearsed.

Forgetting painful memories and traumas may help people cope better. While these events might not be entirely forgotten, forgetting the vivid details can help blunt the difficult emotions that are attached to those memories and make them easier to live with.

Other Explanations for Forgetting

There are also a number of other factors that can play a role in why people forget. Other common causes of forgetfulness include:

  • Alcohol: Drinking alcohol can have a negative effect on memory, so it is best to stick to no more than one or two drinks per day.
  • Depression: Common symptoms of depression include low mood and loss of interest, but difficulty concentrating and forgetfulness can also occur with depressive disorders.
  • Lack of sleep: Sleep plays an important role in memory consolidation, so a lack of quality sleep can have a negative impact on your memory.
  • Medications: Some medications can affect memory including antidepressants, sedatives, and cold and allergy medications.
  • Stress: Excessive stress, both acute and chronic, can also play a role in causing forgetfulness.
  • Age: Age-related forgetting is common and normal since people tend to experience certain types of cognitive declines as they grow older. However, significant problems with forgetting as a person ages may be a sign of a more serious problem such as Alzheimer's disease.

If you are concerned about your forgetting or if it is accompanied by other symptoms, talk to your doctor. Early intervention may help improve outcomes for some memory problems and conditions, so it is important to seek help right away.

How to Minimize Forgetting

While some forgetting is inevitable, there are some things you can do to help cement important information in your memory. Some practices that may help reduce forgetfulness include:

  • Exercise: Research suggests that exercise can lead to rapid improvements in memory function. There's no need to spend hours on the treadmill or at the gym to get this benefit. Results suggest that brief, very light exercise leads to quick enhancements in memory function.
  • Get plenty of sleep: Adequate sleep is essential for both physical and mental health. While sleep needs can vary, the typical recommendation for adults is seven to nine hours per night.
  • Rehearse the information: Sometimes the best way to commit something to memory and reduce the chances it will be forgotten is to use the old standby: rehearsal. Go over the information repeatedly until you've committed it to memory.
  • Write it down: When all else fails, write down important information so that you can refer to it later. In some cases, the act of writing it down may actually help you remember it more later.

While forgetting is often viewed negatively, it can actually help improve memory. Being able to let go of irrelevant memories and only hold on to the important information helps keep those saved memories stronger, a phenomenon known as adaptive forgetting.

A Word From Verywell

While forgetting is not something that you can avoid, understanding the reasons for it can be useful. There are a number of reasons why you forget. In some cases, a number of factors may influence why you struggle to recall information and experiences. Understanding some of the factors that influence forgetting can make it easier to put memory-improvement strategies into practice.

Frequently Asked Questions

  • What are the three causes of forgetting?

    Forgetting can happen for a number of reasons. Three common explanations include depression, lack of sleep, and stress. However, it can also occur due to medical conditions, brain disorders, substance use, and other reasons. You should always talk to your doctor if you are concerned about your memory or find yourself forgetting more than normal.

  • What are the 4 types of forgetting?

    The four main types of forgetting are decay, interference, failure to store, and motivated forgetting.

  • What is forgetting a symptom of?

    Forgetting is often normal, but it can also be a symptom of a number of conditions including depression, infections, brain disorders, or Alzheimer's disease. It can also be happen as a side effect of some medications.

  • What is forgetting called in psychology?

    Forgetting is also sometimes referred to as disremembering. The loss of memory of events from the past is known as amnesia, which can be retrograde (which affects the ability to access old memories) or anterograde (which affects the storage of new memories).

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Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kendra Cherry, MSEd
Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."