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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
Retrieval
Stimulus
Sensory
memory
Attention
Forgetting
Short-term
memory
Encoding
Forgetting
Long-term
memory
Forgetting
Sensory Memory
• Stores all the stimuli that
register on the senses
• Lasts up to three seconds
Sensory
Input
Sensory
Memory
• Two types
– Iconic memory
• Visual
• Usually lasts about 0.3
seconds
• Sperling’s tests (1960s)
– Echoic memory (we’ll
come back to this)
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
Sensory
Input
Sensory
Memory
Attention
Working or
Short-term
Memory
Memorize the following list of numbers:
18121941177614922001
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)
893194434925021578416685061209488885687727
31418610546297480129497496592280
Long-term Memory
• Once information passes from
sensory to short-term memory, it can
be encoded into long-term memory
Retrieval
Sensory
Input
Attention
Sensory
Memory
Working or
Short-term
Memory
Encoding
Long-term
memory
Long-term memory - Encoding
• Elaborative rehearsal
– A technique for transferring information into longterm 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
Bus
Truck
Ambulance
Orange
House
Fire Engine
Fire
Yellow
Green
Red
Apples
Cherry
Roses
Sunrise
Daisies
Flowers
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 and
recovered 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