Human Memory

It is good to have an end to journey towards; but it is the journey that matters, in the

end.Ursula K. Le Gui

Memory

• Process by which information is:– Acquired

• Encoding

– Stored in the brain• Storage

– Later retrieved• Retrieval

– Eventually (possibly) forgotten

Information-Processing Model of Memory

• Computer as a model for our memory

• Three types of memory– Sensory memory– Short-term memory (STM)– Long-term memory (LTM)

• Can hold vast quantities of information for many years

Information-Processing Model of Memory

Short-termmemoryStimulus

Sensorymemory

Long-termmemory

Attention Encoding

Retrieval

Forgetting ForgettingForgetting

Sensory Memory

• Stores all the stimuli that register on the senses

• Lasts up to three seconds• Two types

– Iconic memory• Visual• Usually lasts about 0.3

seconds• Sperling’s tests (1960s)

– Echoic memory (we’ll come back to this)

Sensory

InputSensory Memory

Sperling’s Experiment

• Presented matrix of letters for 1/20 seconds– Report as many letters as

possible

• Subjects recalled only half of the letters

• Was this because subjects didn’t have enough time to view entire matrix? – No

• How did Sperling know this?

Sperling’s Iconic Memory Experiment

Sperling’s Iconic Memory Experiment

Sperling’s Iconic Memory Experiment

Sperling’s Iconic Memory Experiment

Sperling’s Experiment

• Sounded low, medium or high tone immediately after matrix disappeared– Tone signaled 1 row to

report

– Recall was almost perfect

• Memory for images fades after 1/3 seconds or so, making report of entire display hard to do

High

Medium

Low

Sensory Memory

• Echoic memory– Sensory memory for auditory input

that lasts only 2 to 3 seconds

• Why do we need sensory memory?

Short-term Memory

• Function– Conscious processing of information– Attention is the key

• Limits what info comes under the spotlight of short-term memory at any given time

• AKA working memory

Working orShort-term

Memory

Sensory

Input

Sensory Memory

Attention

Memorize the following list of numbers:

1 8 1 2 1 9 4 1 1 7 7 6 1 4 9 2 2 0 0 1

Write down the numbers in order.

Now, try again…

1812 1941 1776 1492 2001

Short-term Memory

• Limited capacity– Can hold 7 ± 2 items for about 20 seconds– Maintenance rehearsal

• The use of repetition to keep info in short-term memory

• CHUNK– Meaningful unit of information– Without rehearsal, we remember 4 ± 2 chunks– With rehearsal, we remember 7 ± 2 chunks– Ericsson & Chase (1982)

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Long-term Memory

Working orShort-term

Memory

Sensory

Input

Sensory Memory

AttentionLong-term

memory

Retrieval

• Once information passes from sensory to short-term memory, it can be encoded into long-term memory

Encoding

Long-term memory - Encoding

• Elaborative rehearsal– A technique for transferring information into

long-term memory by thinking about it in a deeper way

• Levels of processing– Semantic is more effective than visual or

acoustic processing– Craik & Tulving (1975)

• Self-referent effect– By viewing new info as relevant to the self, we

consider that info more fully and are better able to recall it

Long-term memory

• Procedural (Implicit)– Memories of behaviors, skills, etc.

• Demonstrated through behavior

• Declarative (Explicit)– Memories of facts

• Episodic – personal experiences tied to places & time

• Semantic – general knowledge– Semantic network

Semantic Networks

Red

Fire

Cherry

Roses

Fire Engine

Apples

House

Green

Flowers

Daisies

Yellow

Orange

Truck

Bus

Ambulance

Sunrise

Sunsets Clouds

Retrieval

• Retrieval– Process that controls flow of information

from long-term to working memory store

• Explicit memory– The types of memory elicited through

the conscious retrieval of recollections in response to direct questions

• Implicit memory– A nonconscious recollection of a prior

experience that is revealed indirectly, by its effects on performance

Retrieval – Explicit Memory

• Free-recall test– A type of explicit memory task in which a

person must reproduce information without the benefit of external cues

• Recognition task– A form of explicit memory retrieval in which

items are presented to a person who must determine if they were previously encountered

• Retrieval failure– Tip-of-the-tongue (Brown & McNeill)

Retrieval – Explicit Memory

• Context-Dependent Memory– We are more successful at retrieving

memories if we are in the same environment in which we stored them

• State-Dependent Memory– We are more successful at retrieving

memories if we are in the same mood as when we stored them

Retrieval – Implicit Memory

• Showing knowledge of something without recognizing that we know it

• Research with amnesics• Déjà vu

– The illusion that a new situation is familiar

• Eyewitness testimony– Eyewitness transference

• Unintentional plagiarism

Forgetting

If we remembered everything, we should on most occasions be as ill off as if we remembered nothing.

William James• Lack of encoding

– Often, we don’t even encode the features necessary to ‘remember’ an object/event

• Decay– Memory traces erode with the passage of time– No longer a valid theory of forgetting– Jenkins & Dallenbach (1924)

Interference theory

• Forgetting is a result of some memories interfering with others– Proactive interference

•Old memories interfere with ability to remember new memories

– Retroactive interference•New memories interfere with ability to

remember old memories

– Interference is stronger when material is similar

Forgetting

• Repression– There are times when we are unable

to remember painful past events– While there is no laboratory

evidence for this, case studies suggest that memories can be repressed for a number of years andrecovered in therapy

Memory Construction

• Schema theory– Preconceptions about persons, objects, or

events that bias the way new information is interpreted and recalled

• Misinformation effect– The tendency to incorporate false postevent

information into one’s memory of the event itself

• Illusory memories– People sometimes create memories that are

completely false

Improving Memory

• Practice time– Distribute your studying over time

• Depth of processing– Spend ‘quality’ time studying

• Verbal mnemonics– Use rhyming or acronyms to reduce

the amount of info to be stored

Improving Memory

• Method of loci– Items to be recalled are mentally placed in

familiar locations

• Interference– Study right before sleeping & review all the

material right before the exam– Allocate an uninterrupted chunk of time to

one course

• Context reinstatement– Try to study in the same environment &

mood in which you will be taking the exam