Week 5 Cognitive Long Term Memory

Long Term Memory Defination

LTM or long term memory can be described as a place for

storing large amounts of information for indefinite periods of time.

LTM is often thought of as a treasure chest of memories or scrape

book of memories

Capacity

What is the capacity of LTM?

Thomas Landauer (1986) has tried to provide the answer

by making two estimates

a) The size of the human brain is equal to the no of

synapses in the Cerebral Cortex = 1013, which is the no of bits of

information stored in the brain

b) Another estimate is 1020 bits of information which is the

no is neuronal transmission made by average human lifetime

Coding in LTM

Errors made while recalling information from LTM are likely

to be semantic confusion.

Forgetting theories

• Poor encoding

theories

• Decay theories

• Interference

theories

• Retrieval-cue

theories

Forgetting as encoding failure

• Info never encoded into LTM

• What letters accompany the

number 5 on your telephone?

• Where is the number 0 on your

calculator?

• According to this theory, objects

seen frequently, but info never

encoded into LTM

Forgetting as retrieval failure

• Not all forgetting is due to encoding failures

• Sometimes info IS encoded into LTM, but

we can’t retrieve it

Tip of the tongue phenomenon

Retrieval failure theories

• Decay theories

• Interference theories

• Retrieval cue theories

Decay theories

• Memories fade

away or decay

gradually if unused

• Time plays critical

role

• Ability to retrieve

info declines with

time after original

encoding

Biology-based theory

• When new memory formed, it creates

a memory trace

– a change in brain structure or chemistry

• If unused, normal brain metabolic

processes erode memory trace

• Theory not widely favored today

– info CAN be remembered decades after

original learning

• even if unused since original learning

Interference theories

“Memories interfering with

memories”

• Forgetting NOT caused by mere

passage of time

• Caused by one memory

competing with or replacing

another memory

• Two types of interference

Type of Interference theoreis

1. Proactive

   • Opposite of retroactive

   interference

   • When an OLD memory

   interferes with

   remembering NEW

   information

   • Example: Memories of

   where you parked your

   car on campus the past

   week interferes with

   ability find car today

2. Retroactive

   1. When a NEW memory interferes

      with remembering OLD

      information

      • Example: When new phone

      number interferes with ability to

      remember old phone number

   2. Example: Learning a new language interferes

      with ability to remember old language

Retrieval cue theories

Retrieval cue - a clue, prompt

or hint that can help memory

retrieval

• Forgetting the result of using

improper retrieval cues

Recall vs. Recognition tests

• Importance of retrieval cues evident in

recall vs. recognition tests

• Recall tests - must retrieve info learned

earlier

– Examples: Fill-in-the-blank test; essay exams

• Recognition tests - only need to

identify the correct answer

– Example: Multiple choice tests

Which retrieval cues

work best?

• Encoding specificity principle -

cues used during initial

learning more effective during

later retrieval than novel cues

Which retrieval cues

work best?

• Context-dependent memory - improved ability to

remember if tested in the same environment as the

initial learning environment

– Better recall if tested in classroom where you

initially learned info than if moved to a new

classroom

– If learning room smells of chocolate or mothballs,

people will recall more info if tested in room with

the same smell

• compared to different smell or no smell at all

Context dependent effects

• Time of day is also important

for memory retrieval; recall can vary depending on whether individuals are tested at the same time they learned the material.

State-dependent effects

for optimal recall, as memory retrieval can be better when conducted at the same time of day as encoding.

• Recall improved if internal physiological

or emotional state is the same during

testing and initial encoding

• Context-dependent - external,

environmental factors

• State-dependent - internal,

physiological factors

–Mood or emotions also a factor

–Bipolar depressives

• Info learned in manic state, recall

more if testing done during manic

state

• Info learned in depressed state, recall

more if testing done during depressed

state

The spacing effect

Better to study for several shorter periods

than for one longer period

• One hour per day for 8 days leads to

better recall than 8 hours of cramming!

• Why? Encoding variability: best to

encode in a variety of ways, to attach a

wider variety of memory cues to the

material. Spacing practice sessions allows

for more variability.

Subdivisions of long-term

memory

• Semantic memory: general knowledge

• Episodic memory: events in which you

participated

• Explicit memory: consciously recollected

• Implicit memory: not consciously

recollected, but shown in other ways

Declarative vs. procedural

memory

• Procedural memory: how to do things

• Declarative memory: facts, information,

ideas

Reconstructive memory

the process of remembering by piecing together memories based on cues and previous experiences, which can lead to inaccuracies.

• Retelling of stories leads to distortions in

what is remembered.

• Eyewitness memory is subject to distortion

when leading questions are asked.

– “Did another car pass the red Datsun at the

stop sign?”

– The sign was actually a yield sign.

– Participants later falsely recognized the stop

sign 59% of the time.

Eyewitness testimony

• Recall not an exact replica of original

events

• Recall a construction built and rebuilt from

various sources

• Often fit memories into existing beliefs or

schemas

• Schema - mental representation of an

object, scene or event

– Example: schema of a countryside may include green

grass, hills, farms, a barn, cows etc.

Eyewitness testimony

• Scripts - type of schema

– Mental organization of events in time

–Example of a classroom script: Come

into class, sit down, talk to friends, bell

rings, instructor begins to speak, take

notes, bell rings again; leave class etc.

Memory distortion

• Memory can be distorted as

people try to fit new info into

existing schemas

• Giving misleading information after

an event causes subjects to

unknowingly distort their memories

to incorporate the new misleading

information

Loftus experiment

• Subjects shown video

of an accident

between two cars

• Some subjects asked:

How fast were the

cars going when the

smashed into each

other?

• Others aksed: How

fast were the cars

going when the hit

each other?

Autobiographical memory

• Real-world memories are more durable than

laboratory memories of word lists.

• Some items are forgotten because they are

hard to distinguish from other, similar

memories.

• Single-event memories are often combined

into extended or summarized events.

• Rare actions are more likely to be recalled

than frequent actions.

False memory creation

• “You went on a shopping trip with your

mom and your cousin. Somehow, you

wandered away in the store and got lost. A

security guard found you and you were

reunited with your mom about an hour

later.”

• This event never happened. But after

repeated questioning, 29% of participants

“recalled” details of the false event!

The Deese/Roediger-McDermott paradigm

• Study of list of words related to sleep:

Dark

Dream

Pillow

Nap

Night

Quiet

• 80% of participants false recognize “sleep” as

having been on the list, although it wasn’t.

Amnesia

• Anterograde amnesia: inability to learn new

information after the initial point of memory

loss (“H.M.”)

• Old memories in LTM remain intact.

• General knowledge and skills remain intact.

• Retrograde amnesia: loss of memory for

information stored before the point of memory

loss

• Spares “overlearned” information, and skills