Memory overview

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  • Our essence
  • This presentation contains materials which are presented due to the Fair Use exception to US Copyright Law. Further use of these materials is prohibited without the express consent of the copyright holder.

Memory overview

  • A complex concept
  • Refers to both the process of retaining information, and
  • the information retained
  • Many types, uses, and tests
  • What are we without it?

A huge problem

  • Eye witness testimony
  • Witnesses are not always
  • right, even if they are certain
  • Picking the wrong “rapist”
  • How could this happen?

The strange case of h. m.

  • Suffered from severe, recurrent epileptic seizures
  • In desperation, his hippocampus was removed
  • Sure, his seizures decreased in severity and frequency,
  • But, forever after, he “was preoccupied, with 1955”

Who is that?

  • H. M. suffered almost complete anterograde amnesia – no new LTM
  • Every day, even 20 seconds, his memory was wiped clean
  • He couldn’t recognize his wife as she aged, even himself
  • He also demonstrated some retrograde amnesia

Amazingly though, ..

  • H. M. despite his appalling deficits, could learn new skills, aspects of procedural memory
  • On the other hand, he did not know that he had acquired the new skill, an aspect of declarative memory

Memory reconstruction

  • The problem is more than just forgetting
  • We exaggerate, distort, and expand what we “remember
  • Above all, memory is selective
  • We typically remember best the gist of the event
  • The details can be much more elusive

A preference for the mundane

  • What we “remember” of events is often a mixture of surviving memories and what we expect must have happened
  • We alter some memories so that, in hindsight, they make sense
  • But life is truly stranger than fiction

A Common Wild-Card – Source Misattribution

  • Often it is far easier to remember something than it is to recall where we heard it
  • Since we experience or pick up so much information, from sources which vary greatly in credibility, this can lead to errors
  • Others call it source amnesia

Flashbulb memories

  • Traumatic, highly emotional and compelling memories seem to be automatically encoded
  • These memories are indelibly seared into our memories
  • We remember in astonishing detail
  • Or do we?
  • President Kennedy’s
  • assassination
  • The Challenger explosion
  • But research conducted
  • in the wake 9/11, show that
  • even these memories decay

Assessing memory

  • 1) Recall – Producing the desired information without any cues or hints
  • Short answer/essay tests
  • Vulnerable to interference
  • 2) Cued recall – Producing the information with hints
  • Class picture for kindergarten names
  • 3) Recognition – Picking out the desired information from a number of alternatives
  • Multiple choice tests
  • 4) Relearning – learning something for the second time
  • Usually reveals “savings”, information relearned much more quickly

Memory systems

  • Implicit Memory – memories which are influenced by experiences, often without awareness
  • Easier to do than explain
  • This memory system is often primed, or prepared, by events on the fringe of our attention
  • The cocktail-party effect

Now for a little memory exercise

  • You will be asked to consider 20 words.
  • They will be broken into two groups.
  • The groups will alternate.
  • For the first group decide if the word has 6 or less letters.
  • For the second, consider if the word recalls pleasant or sad memories.

Information processing view

  • Based on a computer model conception of memory
  • Proposes that information enters the system, is processed and coded in various ways and then stored
  • Sets out three
  • components

Sensory store

  • The first filter
  • A very brief capture of sensory information
  • We can attend to anything in our visual field
  • But if we do not attend to something, it is lost

Short-term memory

  • Temporary storage of information you have just experienced
  • Lasts for about 20 seconds, unless rehearsed
  • Holds 7 (plus or minus 2) items, like a crowded elevator holds passengers
  • Can be effectively extended by memorizing information in chunks – meaningful units

Long-term memory

  • Unlimited capacity
  • Lasts (usually) as long as you do
  • Weakened by interference
  • Also vulnerable to loss of retrieval cues
  • Usually located in the frontal lobes
  • Meaningful, distinctive material goes in quickly

The working memory theory

  • Over time, the information processing theory’s concept of short term memory sprung more and more leaks
  • Why do some things go straight into long term storage, while others never do?
  • From these and many other concerns, the concept of working memory began to emerge

More “working”

  • A system for processing or ‘working’ with current information
  • The thoughts, facts, ideas, and feelings in our current sphere of attention
  • Some of these items might eventually be stored in LTM, others might not

Procedural memories

  • Memory of skills, procedures, habits, even conditioned responses
  • A subset of the implicit memory system
  • There are plenty of things that we can easily do, but have great difficulty describing
  • Very hard to “forget”
  • Riding a bike, typing, tying a tie, etc.

Declarative memory

  • Contrasts with implicit/procedural memory
  • Consists of memories we can easily state in words
  • What we know verbally
  • We can lose this type of memory and yet retain implicit/procedural memories

More memory types

  • Semantic – memory of general principles
  • Quite resistant to decay
  • Episodic – memory of specific events
  • Vulnerable to decay
  • Combination leads to source amnesia
  • “I heard about that, but I can’t remember where.”

The Biology of Memory

  • We don’t gain memories without chemical and structural changes in our neurons
  • For short-term memory changes consist of a temporary change in the ability to release neurotransmitters

A Change in Structure

  • For long-term memory the neuronal changes are more basic and lasting
  • A new long-term memory causes changes in synaptic responsivity – long-term potentiation
  • Exchanges between these neurons are chemically strengthened, and much more likely to communicate in the future

More changes

  • Not only are these neurons synapses chemically strengthened,
  • The neurons grow more dendrites and forge more synapses
  • This happens over time, a process called consolidation

But where are they?

  • Short-term – frontal lobes
  • Long-term – hippocampus is essential, but after processing, they go to the cerebral cortex areas involved in their perception
  • Any single memory is a complex relationship of neurons scattered throughout the cerebral cortex, linked together at the start by the hippocampus

Emotional arousal

  • We usually remember emotionally arousing events but the accuracy of the memory can suffer
  • Arousal increases hormone levels which excite the amygdala, which works with the hippocampus to ensure storage
  • Now write down as many as you can of the 20 words you were asked to consider earlier in class.
  • Which group won?

Long-term memory storage

  • To improve our memory we must improve the way we store information
  • Just repeating things, over and over again, will not help us remember them
  • We must process (work with) them deeply

Levels of processing

  • Our ease in retrieving a memory depends on the number and types of links we make with it
  • The more links or connections we make with the information, the better we will remember it
  • Use links that mean something to you

The crucial focus

  • “How does this information apply to some experience in my own life?”
  • Make it your own and it will be yours forever.
  • Also known as elaborative rehearsal

Mnemonic devices

  • Any memory aid that relies on encoding each piece of information in a specific way
  • String items together in a story
  • Method of loci – link
  • concepts or ideas with
  • places, or a path
  • Clever, unusual images
  • are essential

Memory loss

  • We don’t need to remember everything
  • Those with super memory pay for it
  • But often, we regret forgetting things
  • How do we forget?
  • 1) Interference similar experiences
  • 2) Decay information fades away, some in mere seconds
  • 3) Loose cues retrieval problems

Ebbinghaus & Interference

  • Pioneered systematic study
  • Memorized thousands of strings
  • of nonsense syllables
  • Years later, novices trounced him in tests
  • How?
  • Proactive interference – work with similar material in the past makes learning new material more difficult

More interference

  • Retroactive interference – work with new material makes old material harder to remember
  • Effect weakened by going to sleep right after learning information
  • No wonder ads shown during TV programs with violent/sexual content are routinely forgotten

Losing cues – losing memories

  • We need cues to retrieve memories that we have not processed for a while
  • The memories are likely still there, but finding them among billions of neurons can be near impossible

Encoding specificity

  • Associations formed while learning are the most effective retrieval cues
  • This classroom
  • This time of day
  • Same chair
  • Same people

State-dependent memory

  • Tendency to remember something better if your body is in a similar condition when you attempt to recall it, as it was when you first learned it
  • Mood – cognitive view of depression
  • Drugs – if you studied under the influence, you should …..
  • Small effects


  • Timing spreading studying sessions over time aids retention
  • Even if you are able to devote a significant amount of uninterrupted attention to the material in one setting, you won’t remember it as well


  • Are some things so traumatic that we involuntarily push them out consciousness
  • Into the unconscious?
  • Though Freud based many of his theories on this phenomenon, it doesn’t work that way.
  • In fact, we often find it difficult to stop thinking about horrible experiences

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