July 15, 2020  |  Purdue Global

The human brain is a wonder of engineering, with 86 billion neurons, 400 miles of capillaries, 100,000 miles of nerve fibers, and more than 10 trillion synapses. Every day, many new memories are loaded into it.

How much memory can your brain store? Research published on eLife Sciences states your brain can hold the computer equivalent of 1 petabyte, equal to 1 million gigabytes or 4.7 billion books. So why is our memory so fragile?

Find out about human memory, how memory works, how it stops working, and how to improve memory below.

How Memory Works

Stages of Memory

Memory takes place in stages, which explains the basic structure and function of memory. It ranges from very brief to long-term memories that potentially stick with us throughout our lives. A description of this process called the Atkinson-Shiffrin model is used often as a description of the three-stage structure of memory.


Sensory memory occurs at the earliest stage of memory. Sensory information from the environment is stored for a brief period of time during this stage. Generally, this is for no longer than a half-second for visual information, such as shape, color, size, and location. For auditory information, the storage is no longer than 3 or 4 seconds.

Visual memory mistakes are to blame for many wrongful criminal convictions, according to The Innocence Project. The group says approximately 71% of more than 300 convictions overturned in the United States were due to faulty memories.

Out of 300+ convictions in the U.S., 71% were overturned due to faulty memory


Short-term memory, also known as active memory, is the information we are currently aware of or are thinking about. An example of this would be looking up an old password and remembering it long enough to type it in. Most of the information in active memory lasts up to 30 seconds.

Researchers indicate that attention spans are becoming shorter, based on the observation that people are spending less time on a number of online sites such as Twitter, Wikipedia, and Reddit.

An image representing a computer screen


Long-term memory refers to the continuing storage of information. Some of this information is fairly easy to recall, while other memories are much more difficult to access. Our long-term memory mechanism seems to have almost unlimited capacity.

Process of Memory

The system for saving memories also occurs in stages. According to the American Psychological Association, it’s widely understood that there are three major processes involved in memory: encoding, storage, and retrieval.


To form new memories, information must be changed into a usable form. This takes place through the process known as encoding. A number of factors affect encoding, such as the level of processing, the timing of encoding, or the way a person organizes information.


When the information has been encoded successfully, it must be stored in memory for later use. This stored memory lies outside of our awareness most of the time, until we need it.

The average weight of a brain in an adult man is 2.9 pounds and 2.6 pounds in an adult woman, according to the National Institutes of Health.

Brains on scales showing 2.9 pounds and 2.6 pounds


Stored memories are brought into conscious awareness during the retrieval process. Although memories are safely stored, retrieval isn’t perfect. The process can be blocked by several different factors, which is why we forget things.

How We Forget Things

Forgetting doesn’t seem to occur at a constant rate. Some forgetting seems to happen quickly. On the other hand, research from the American Psychological Association shows that what you remember after three years is likely to stay with you the rest of your life.

Memory researcher and expert Elizabeth Loftus has proposed the following explanations for why we forget.

Retrieval Failure

Sometimes the memories are there, but we just can't seem to access them. Two of the basic reasons for this failure in memory retrieval are related to encoding failures and lack of retrieval cues. With encoding failures, memories fail to take hold. With lack of retrieval cues, memories are stored but hard to retrieve because of something akin to filing errors.


Some information may be blocked or disrupted when we’re trying to access it. This seems to be a primary source of forgetting. There are two main ways interference can block retrieval of memories.

  • Retroactive interference—This happens when newly acquired information impedes old memories. For example, when trying to remember a new password, you instead remember the old one.
  • Proactive interference—This is when previously learned information makes it more difficult to form new memories. For example, a friend’s changed phone number might be blocked from memory by their old phone number.

Failure to Store

A common reason why we don't remember information is because it never made it into long-term memory in the first place. This information stayed in sensory or short-term memory without being stored.

Motivated Forgetting

Sometimes we may actively work to forget memories. This can happen especially with memories of traumatic or disturbing events or experiences.

How Memory Is Compromised

Memory Loss and Aging

Age-related memory loss is normal. It shouldn’t hamper someone from living a full, productive life. Changes in memory generally are manageable and don't disrupt your ability to work, live independently, or maintain a social life.

By age 80, up to 20% of the nerve connections to the brain’s memory center, the hippocampus, can be lost, the National Institutes of Health reports.

By age 80, up to 20% of the nerve connections to the brain's memory center can be lost.

Memory Loss and Dementia

Dementia is a set of symptoms, such as impairment in thinking skills, judgment, language, memory, and reasoning. Often, life-disrupting memory loss is one of the first signs of dementia.

Many medical problems can cause memory loss or other dementia-like symptoms, the Mayo Clinic reports. Most of these conditions can be treated.

  • Alcoholism—Chronic alcoholism can have serious consequences for the brain. Alcohol can also interact badly with medications, causing memory loss.
  • Brain diseases—Memory problems or other dementia-like symptoms can be caused by physical conditions such as a brain tumor or infection.
  • Emotional disorders—Forgetfulness, confusion, difficulty concentrating, and other problems that disrupt daily activities can be caused by stress, anxiety, or depression.
  • Hypothyroidism—An underactive thyroid gland can cause forgetfulness and other thinking problems.
  • Medications—Certain medications or a combination of medications can cause forgetfulness or confusion.
  • Minor head trauma or injury—A head injury from a fall or accident can cause memory problems.
  • Vitamin B12 deficiency—Healthy nerve cells and red blood cells are maintained by vitamin B12. A deficiency in the vitamin, which is common as we age, can affect memory.

How to Improve Your Memory

There are some research-driven techniques for improving memory. They can effectively enhance recall and increase retention of information.

  • Change your routine to shake up your brain.
  • Exercise for your body’s health, which helps your brain, too.
  • Focus on difficult information first.
  • Get rid of external distractions.
  • Eat healthy foods, which helps memory.
  • Improve sleep to help you learn faster and remember better.
  • Practice mindfulness to aid in concentration and memory.
  • Organize information by concepts and terms.
  • Read out loud to enhance understanding and recall.
  • Rehearse information to encode it in long-term memory.
  • Relate new information to things you already know.
  • Take in information regularly, not all at once.
  • Use mnemonics with positive imagery, humor, or novelty.
  • Use visualization (photographs, charts, and graphics).

Other Facts About Memory

  • Being tested on information helps you remember it better.
  • Caffeine only helps to increase alertness; it doesn’t maintain memory performance.
  • Depictions of amnesia in movies are usually inaccurate.
  • Human minds can create, reinvent, distort, or exaggerate a memory after any traumatic experience or event.
  • It is possible to erase bad memories.
  • Left-handed people have better memories.
  • Most adult memories are from when we were between 15 and 25 years old.
  • New brain connections are created every time you form a memory.
  • The memory starts to work just 20 weeks after conception.
  • Your memory can associate a scent with a particular occurrence or event.

Further Your Education With Purdue Global

Fill your memory with information that will help you meet your career goals. Let Purdue Global help you. Contact us to learn how to expand your education.

About the Author

Purdue Global

Purdue Global delivers a fully personalized, world-class education online that's tailored for adults. We offer 175 programs, including associate's, bachelor's, master's, and doctoral degrees as well as certificates, in areas such as business, IT, education, health sciences, nursing, criminal justice, and more.

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