Browse Content (/browse-content) / Forgetting and Amnesia

Forgetting and Amnesia

By Nicole Dudukovic (/authors/nicole-dudukovic) and Brice Kuhl (/authors/brice-kuhl)
New York University

This module explores the causes of everyday forgetting and

considers pathological forgetting in the context of amnesia.
Forgetting is viewed as an adaptive process that allows us to be
efficient in terms of the information we retain.

Tags: Anterograde amnesia, Consolidation, Decay, Declarative memory, Dissociative amnesia, Encoding,
Interference, Medial temporal lobes, Retrieval, Retrograde amnesia,
Temporally graded retrograde amnesia

Learning Objectives
Identify five reasons we forget and give examples of each.

Describe how forgetting can be viewed as an adaptive process.

Explain the difference between anterograde and retrograde amnesia.

Introduction

Chances are that you have experienced memory lapses and been frustrated by them. You may
have had trouble remembering the definition of a key term on an exam or found yourself unable
to recall the name of an actor from one of your favorite TV shows. Maybe you forgot to call your
aunt on her birthday or you routinely forget where you put your cell phone. Oftentimes, the bit
of information we are searching for comes back to us, but sometimes it does not. Clearly,
forgetting seems to be a natural part of life. Why do we forget? And is forgetting always a bad
thing?
 Forgetting can often be obnoxious or even embarrassing. But as we
explore this module, you’ll learn that forgetting is important and
necessary for everyday functionality. [Image: jazbeck,
https://goo.gl/nkRrJy, CC BY 2.0, https://goo.gl/BRvSA7]

Causes of Forgetting

One very common and obvious reason why you cannot remember a piece of information is
because you did not learn it in the first place. If you fail to encode information into memory, you
are not going to remember it later on. Usually, encoding failures occur because we are
distracted or are not paying attention to specific details. For example, people have a lot of
trouble recognizing an actual penny out of a set of drawings of very similar pennies, or lures,
even though most of us have had a lifetime of experience handling pennies (Nickerson & Adams,
1979). However, few of us have studied the features of a penny in great detail, and since we
have not attended to those details, we fail to recognize them later. Similarly, it has been well
documented that distraction during learning impairs later memory (e.g., Craik, Govoni, Naveh-
Benjamin, & Anderson, 1996). Most of the time this is not problematic, but in certain situations,
such as when you are studying for an exam, failures to encode due to distraction can have
serious repercussions.

Another proposed reason why we forget is that memories fade, or decay, over time. It has been
known since the pioneering work of Hermann Ebbinghaus (1885/1913) that as time passes,
memories get harder to recall. Ebbinghaus created more than 2,000 nonsense syllables, such as
dax, bap, and rif, and studied his own memory for them, learning as many as 420 lists of 16
nonsense syllables for one experiment. He found that his memories diminished as time passed,
with the most forgetting happening early on after learning. His observations and subsequent
research suggested that if we do not rehearse a memory and the neural representation of that
memory is not reactivated over a long period of time, the memory representation may
disappear entirely or fade to the point where it can no longer be accessed. As you might
imagine, it is hard to definitively prove that a memory has decayed as opposed to it being
inaccessible for another reason. Critics argued that forgetting must be due to processes other
than simply the passage of time, since disuse of a memory does not always guarantee forgetting
(McGeoch, 1932). More recently, some memory theorists have proposed that recent memory
traces may be degraded or disrupted by new experiences (Wixted, 2004). Memory traces need to
be consolidated, or transferred from the hippocampus to more durable representations in the
cortex, in order for them to last (McGaugh, 2000). When the consolidation process is interrupted
by the encoding of other experiences, the memory trace for the original experience does not get
fully developed and thus is forgotten.

Both encoding failures and decay account

for more permanent forms of forgetting, in
which the memory trace does not exist, but
forgetting may also occur when a memory
exists yet we temporarily cannot access it.
This type of forgetting may occur when we
lack the appropriate retrieval cues for
bringing the memory to mind. You have
probably had the frustrating experience of
forgetting your password for an online site.
Usually, the password has not been
permanently forgotten; instead, you just
need the right reminder to remember what
it is. For example, if your password was
At times, we will completely blank on something we’re “pizza0525,” and you received the
certain we’ve learned - people we went to school with password hints “favorite food” and “Mom’s
years ago for example. However, once we get the right birthday,” you would easily be able to
retrieval cue (a name perhaps), the memory (faces or retrieve it. Retrieval hints can bring back to
experiences) rushes back to us like it was there all mind seemingly forgotten memories
along. [Image: sbhsclass84, https://goo.gl/sHZyQI, CC (Tulving & Pearlstone, 1966). One real-life
BY-SA 2.0, https://goo.gl/rxiUsF] illustration of the importance of retrieval
cues comes from a study showing that
whereas people have difficulty recalling the
names of high school classmates years after graduation, they are easily able to recognize the
names and match them to the appropriate faces (Bahrick, Bahrick, & Wittinger, 1975). The
names are powerful enough retrieval cues that they bring back the memories of the faces that
went with them. The fact that the presence of the right retrieval cues is critical for remembering
adds to the difficulty in proving that a memory is permanently forgotten as opposed to
temporarily unavailable.

Retrieval failures can also occur because other memories are blocking or getting in the way of
recalling the desired memory. This blocking is referred to as interference. For example, you may
fail to remember the name of a town you visited with your family on summer vacation because
the names of other towns you visited on that trip or on other trips come to mind instead. Those
memories then prevent the desired memory from being retrieved. Interference is also relevant
to the example of forgetting a password: passwords that we have used for other websites may
come to mind and interfere with our ability to retrieve the desired password. Interference can be
either proactive, in which old memories block the learning of new related memories, or
retroactive, in which new memories block the retrieval of old related memories. For both types
of interference, competition between memories seems to be key (Mensink & Raaijmakers, 1988).
Your memory for a town you visited on vacation is unlikely to interfere with your ability to
remember an Internet password, but it is likely to interfere with your ability to remember a
different town’s name. Competition between memories can also lead to forgetting in a different
way. Recalling a desired memory in the face of competition may result in the inhibition of
related, competing memories (Levy & Anderson, 2002). You may have difficulty recalling the
name of Kennebunkport, Maine, because other Maine towns, such as Bar Harbor, Winterport,
and Camden, come to mind instead. However, if you are able to recall Kennebunkport despite
strong competition from the other towns, this may actually change the competitive landscape,
weakening memory for those other towns’ names, leading to forgetting of them instead.

Finally, some memories may be

forgotten because we deliberately
attempt to keep them out of mind. Over
time, by actively trying not to remember
an event, we can sometimes
successfully keep the undesirable
memory from being retrieved either by
inhibiting the undesirable memory or
generating diversionary thoughts
(Anderson & Green, 2001). Imagine that
you slipped and fell in your high school
cafeteria during lunch time, and
everyone at the surrounding tables
laughed at you. You would likely wish to
avoid thinking about that event and
might try to prevent it from coming to mind. One way that you could accomplish this is by
thinking of other, more positive, events that are associated with the cafeteria. Eventually, this
memory may be suppressed to the point that it would only be retrieved with great difficulty
(Hertel & Calcaterra, 2005).

Adaptive Forgetting

We have explored five different causes of

forgetting. Together they can account for
the day-to-day episodes of forgetting that
each of us experience. Typically, we think of
these episodes in a negative light and view
forgetting as a memory failure. Is forgetting
ever good? Most people would reason that
forgetting that occurs in response to a
deliberate attempt to keep an event out of
mind is a good thing. No one wants to be
constantly reminded of falling on their face
in front of all of their friends. However,
beyond that, it can be argued that
forgetting is adaptive, allowing us to be Could you imagine being unable to forget every path
efficient and hold onto only the most you have taken while hiking? Each new trip, you would
relevant memories (Bjork, 1989; Anderson be walking around the forest for days, incapable of
& Milson, 1989). Shereshevsky, or “S,” the distinguishing today’s path from the prior ones. [Image:
mnemonist studied by Alexander Luria Dan Trew, https://goo.gl/8fJWWE, CC BY-SA 2.0,
(1968), was a man who almost never https://goo.gl/rxiUsF]
forgot. His memory appeared to be
virtually limitless. He could memorize a
table of 50 numbers in under 3 minutes and recall the numbers in rows, columns, or diagonals
with ease. He could recall lists of words and passages that he had memorized over a decade
before. Yet Shereshevsky found it difficult to function in his everyday life because he was
constantly distracted by a flood of details and associations that sprung to mind. His case history
suggests that remembering everything is not always a good thing. You may occasionally have
trouble remembering where you parked your car, but imagine if every time you had to find your
car, every single former parking space came to mind. The task would become impossibly difficult
to sort through all of those irrelevant memories. Thus, forgetting is adaptive in that it makes us
more efficient. The price of that efficiency is those moments when our memories seem to fail us
(Schacter, 1999).

Amnesia

Clearly, remembering everything would be

maladaptive, but what would it be like to
remember nothing? We will now consider
a profound form of forgetting called
amnesia that is distinct from more
ordinary forms of forgetting. Most of us
have had exposure to the concept of
amnesia through popular movies and
television. Typically, in these fictionalized
portrayals of amnesia, a character suffers
some type of blow to the head and
suddenly has no idea who they are and
can no longer recognize their family or
remember any events from their past.
Patients with damage to the temporal lobes may After some period of time (or another
experience anterograde amnesia and/or retrograde blow to the head), their memories come
amnesia. [Image: en:Anatomography, flooding back to them. Unfortunately, this
https://goo.gl/ALPAu6, CC BY-SA 2.1 JP, portrayal of amnesia is not very accurate.
https://goo.gl/BDF2Z4] What does amnesia typically look like?

The most widely studied amnesic patient

was known by his initials H. M. (Scoville & Milner, 1957). As a teenager, H. M. suffered from
severe epilepsy, and in 1953, he underwent surgery to have both of his medial temporal lobes
removed to relieve his epileptic seizures. The medial temporal lobes encompass the
hippocampus and surrounding cortical tissue. Although the surgery was successful in reducing
H. M.’s seizures and his general intelligence was preserved, the surgery left H. M. with a
profound and permanent memory deficit. From the time of his surgery until his death in 2008, H.
M. was unable to learn new information, a memory impairment called anterograde amnesia. H.
M. could not remember any event that occurred since his surgery, including highly significant
ones, such as the death of his father. He could not remember a conversation he had a few
minutes prior or recognize the face of someone who had visited him that same day. He could
keep information in his short-term, or working, memory, but when his attention turned to
something else, that information was lost for good. It is important to note that H. M.’s memory
impairment was restricted to declarative memory, or conscious memory for facts and events. H.
M. could learn new motor skills and showed improvement on motor tasks even in the absence
of any memory for having performed the task before (Corkin, 2002).

In addition to anterograde amnesia, H. M. also suffered from temporally graded retrograde

amnesia. Retrograde amnesia refers to an inability to retrieve old memories that occurred
before the onset of amnesia. Extensive retrograde amnesia in the absence of anterograde
amnesia is very rare (Kopelman, 2000). More commonly, retrograde amnesia co-occurs with
anterograde amnesia and shows a temporal gradient, in which memories closest in time to the
onset of amnesia are lost, but more remote memories are retained (Hodges, 1994). In the case
of H. M., he could remember events from his childhood, but he could not remember events that
occurred a few years before the surgery.

Amnesiac patients with damage to the hippocampus and surrounding medial temporal lobes
typically manifest a similar clinical profile as H. M. The degree of anterograde amnesia and
retrograde amnesia depend on the extent of the medial temporal lobe damage, with greater
damage associated with a more extensive impairment (Reed & Squire, 1998). Anterograde
amnesia provides evidence for the role of the hippocampus in the formation of long-lasting
declarative memories, as damage to the hippocampus results in an inability to create this type of
new memory. Similarly, temporally graded retrograde amnesia can be seen as providing further
evidence for the importance of memory consolidation (Squire & Alvarez, 1995). A memory
depends on the hippocampus until it is consolidated and transferred into a more durable form
that is stored in the cortex. According to this theory, an amnesiac patient like H. M. could
remember events from his remote past because those memories were fully consolidated and no
longer depended on the hippocampus.

The classic amnesiac syndrome we have considered here is sometimes referred to as organic
amnesia, and it is distinct from functional, or dissociative, amnesia. Functional amnesia involves
a loss of memory that cannot be attributed to brain injury or any obvious brain disease and is
typically classified as a mental disorder rather than a neurological disorder (Kihlstrom, 2005).
The clinical profile of dissociative amnesia is very different from that of patients who suffer from
amnesia due to brain damage or deterioration. Individuals who experience dissociative
amnesia often have a history of trauma. Their amnesia is retrograde, encompassing
autobiographical memories from a portion of their past. In an extreme version of this disorder,
people enter a dissociative fugue state, in which they lose most or all of their autobiographical
memories and their sense of personal identity. They may be found wandering in a new location,
unaware of who they are and how they got there. Dissociative amnesia is controversial, as both
the causes and existence of it have been called into question. The memory loss associated with
dissociative amnesia is much less likely to be permanent than it is in organic amnesia.

Conclusion

Just as the case study of the mnemonist Shereshevsky illustrates what a life with a near perfect
memory would be like, amnesiac patients show us what a life without memory would be like.
Each of the mechanisms we discussed that explain everyday forgetting—encoding failures,
decay, insufficient retrieval cues, interference, and intentional attempts to forget—help to keep
us highly efficient, retaining the important information and for the most part, forgetting the
unimportant. Amnesiac patients allow us a glimpse into what life would be like if we suffered
from profound forgetting and perhaps show us that our everyday lapses in memory are not so
bad after all.

Outside Resources
Web: Brain Case Study: Patient HM
https://bigpictureeducation.com/brain-case-study-patient-hm
(https://bigpictureeducation.com/brain-case-study-patient-hm)

Web: Self-experiment, Penny demo

http://www.indiana.edu/~p1013447/dictionary/penny.htm
(http://www.indiana.edu/~p1013447/dictionary/penny.htm)

Web: The Man Who Couldn’t Remember

http://www.pbs.org/wgbh/nova/body/corkin-hm-memory.html
(http://www.pbs.org/wgbh/nova/body/corkin-hm-memory.html)

Discussion Questions

1. Is forgetting good or bad? Do you agree with the authors that forgetting is an adaptive
process? Why or why not?

2. Can we ever prove that something is forgotten? Why or why not?

3. Which of the five reasons for forgetting do you think explains the majority of incidences of
forgetting? Why?

4. How is real-life amnesia different than amnesia that is portrayed on TV and in film?
Vocabulary

Anterograde amnesia
Inability to form new memories for facts and events after the onset of amnesia.

Consolidation
Process by which a memory trace is stabilized and transformed into a more durable form.

Decay
The fading of memories with the passage of time.

Declarative memory
Conscious memories for facts and events.

Dissociative amnesia
Loss of autobiographical memories from a period in the past in the absence of brain injury or
disease.

Encoding
Process by which information gets into memory.

Interference
Other memories get in the way of retrieving a desired memory

Medial temporal lobes

Inner region of the temporal lobes that includes the hippocampus.

Retrieval
Process by which information is accessed from memory and utilized.

Retrograde amnesia
Inability to retrieve memories for facts and events acquired before the onset of amnesia.

Temporally graded ​retrograde amnesia

Inability to retrieve memories from just prior to the onset of amnesia with intact memory for
more remote events.

References
Anderson, J. R., & Milson, R. (1989). Human memory: An adaptive perspective. *Psychological
Review*, 96, 703–719.

Anderson, M. C., & Green, C. (2001). Suppressing unwanted memories by executive control.
Nature, 410, 366–369.
Bahrick, H. P., Bahrick, P. O., & Wittinger, R. P. (1975). Fifty years of memory for names and
faces: A cross-sectional approach. Journal of Experimental Psychology: General, 104, 54–75.

Bjork, R. A. (1989). Retrieval inhibition as an adaptive mechanism in human memory. In H. L.

Roediger, III, & F. I. M. Craik (Eds.), Varieties of Memory and Consciousness (pp. 309– 330).
Hillsdale, NJ: Erlbaum.

Corkin, S. (2002). What’s new with the amnesic patient H. M.? *Nature Reviews
Neuroscience*, 3, 153–160.

Craik, F. I. M., Govoni, R., Naveh-Benjamin, M., & Anderson, N. D. (1996). The effects of
divided attention on encoding and retrieval processes in human memory. *Journal of
Experimental Psychology: General*, 125, 159–180.

Ebbinghaus, H. (1913). Memory. A contribution to experimental psychology. New York: Teachers

College/Columbia University (Engl. ed.). (Original work published in 1885.)

Hertel, P. T., & Calcaterra, G. (2005). Intentional forgetting benefits from thought
substitution. Psychonomic Bulletin & Review, 12, 484–489.

Hodges, J. R. (1994). Retrograde amnesia. In A. Baddeley, B. A. Wilson, & F. Watts (Eds.),

Handbook of Memory Disorders (pp. 81–107). New York: Wiley.

Kihlstrom, J. F. (2005). Dissociative disorders. Annual Review of Clinical Psychology, 1, 227–

253.

Kopelman, M. (2000). Focal retrograde amnesia and the attribution of causality: An

exceptionally critical review. Cognitive Neuropsychology, 17, 585–621.

Levy, B. J., & Anderson, M. C. (2002). Inhibitory processes and the control of memory
retrieval. Trends in Cognitive Sciences, 6, 299–305.

Luria, A. R. (1968). The mind of a mnemonist: A little book about a vast memory (L. Solataroff,
Trans.). New York: Basic Books.

McGaugh, J. L. (2000). Memory: A century of consolidation. Science, 287, 248–251.

McGeoch, J. A. (1932). Forgetting and the law of disuse. Psychological Reviews, 39, 352– 370.

Mensink, G., & Raaijmakers, J. G. (1988). A model for interference and forgetting.
*Psychological Review*, 95, 434–455.

Nickerson, R. S., & Adams, M. J. (1979). Long-term memory for a common object. *Cognitive
Psychology*, 11, 287–307.

Reed, J. M. & Squire, L. R. (1998). Retrograde amnesia for facts and events: Findings from
four new cases. Journal of Neuroscience, 18, 3943–3954.

Schacter, D. L. (1999). The seven sins of memory: Insights from psychology and cognitive
neuroscience. American Psychologist, 54, 182–203.

Scoville, W. B. & Milner, B. (1957). Loss of recent memory after bilateral hippocampal lesions.
Journal of Neurology, Neurosurgery, & Psychiatry, 20, 11–21.
Squire, L. R., & Alvarez, P. (1995). Retrograde amnesia and memory consolidation: A
neurobiological perspective. Current Opinions in Neurobiology, 5, 169–177.

Tulving, E., & Pearlstone, Z. (1966). Availability versus accessibility of information in memory
for words. Journal of Verbal Learning and Verbal Behavior, 5, 381–391.

Wixted, J. T. (2004). The psychology and neuroscience of forgetting. *Annual Reviews of

Psychology*, 55, 235–269.

Authors

Nicole Dudukovic
Nicole Dudukovic earned her Ph.D. in Psychology from Stanford University and has
taught courses at Stanford, Trinity College, and New York University. Her research
explores interactions between attention and memory, and she is interested in
applying memory research to other fields, particularly education.

Brice Kuhl
Brice Kuhl earned his Ph.D. in Psychology from Stanford University and completed
postdoctoral work at Yale University. He is currently an Assistant Professor of
Psychology at New York University. His research explores the neural mechanisms
of memory and causes of forgetting.

Creative Commons License

(https://creativecommons.org/licenses/by-nc-sa/4.0/deed.en_US)

Forgetting and Amnesia by Nicole Dudukovic and Brice Kuhl (https://nobaproject.com/modules/forgetting-

and-amnesia#authors) is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0
International License (https://creativecommons.org/licenses/by-nc-sa/4.0/deed.en_US). Permissions beyond
the scope of this license may be available in our Licensing Agreement (https://nobaproject.com/license-
agreement).

How to cite this Noba module using APA Style

Dudukovic, N. & Kuhl, B. (2024). Forgetting and amnesia. In R. Biswas-Diener & E. Diener (Eds),
Noba textbook series: Psychology. Champaign, IL: DEF publishers. Retrieved from
http://noba.to/m38qbftg (http://noba.to/m38qbftg)

SECTIONS

Abstract
 Learning Objectives

Introduction

Causes of Forgetting

Adaptive Forgetting

Amnesia

Conclusion

Outside Resources

Discussion Questions

Vocabulary

References

Authors

Creative Commons License

About (/about-noba) Privacy (/privacy-policy) Terms (/terms-of-service) Licensing (/license-agreement)

Contact (/contact-noba) © 2024 Diener Education Fund Comments or questions? (/contact-noba)