memory--what’s in there?. the problem you have a great deal of stuff in memory: how do you get the...

Memory--what’s in there?

The problem

You have a great deal of stuff in memory:

How do you get the right thing out when you need it?

How do you find the right book in a big storehouse?

An obvious option is to number all the books. This is called an addressing system.

Computer hard drives also use addressing systems.

Your mind clearly does not work this way.

1. More books means slower search2. Slight errors mean possibly big mistakes

It doesn’t take us longer to remember thingsas we learn more. When we make a mistake it’s typically a near miss.

Even more impressive. . .

If you dropped a raw egg from the Eiffel tower, would it break?

How do you know that?

You probably have not observed an egg being dropped from the Eiffel tower, so what happens is not in memory. How, then, do you answer the question?

Your memory system provides relevant facts:Eiffel tower is tallEggs dropped from a great height will break.

Theories of memory designed to account for. . .

• Ready access to lots of information

• Access to relevant information when crucial information is not stored

Network theories

Bird

Time

Bird"Bird"

Node Input from environment

Activation

Collins & Quillian Hierarchical Model

Living thing

Animal

Plant

Bird Fish

ChickenCanary

is a

is a

is a is a

is ais a

sing

yellow

canis

wingshas

feathershas

skin

move

has

can

breathe

eat

must

must

1. Relevant info becomes available (in some versions)2. Accounts for property inheritance (“does a canary breathe?”)3. Accounts for identity questions (“is a canary an animal?”)

Nodes

Links

Problems

• Some of the predictions aren’t borne out (“is a gorilla a mammal?” > “is a gorilla an animal?”)

• Properties don’t seem to be stored only once (e.g., “flies” is a property that people strongly associate with robins, bluebirds, wrens, etc.)

Collins & Loftus

Spreading activation along unlabeled nodes.Node

Unlabeled link with weight

Input from environment

Congress

White House

Bush

Congress

White House

Bush

Congress

White House

Bush“Bush”

activationActivation spreads

Time

Example

Same information

• Units• State of activation. • Output function. • Pattern of

connectivity=knowledge• A activation

rule:integrate input• Learning rule.

Properties of networks

• Allows retrieval of properties.

• Allows content-addressable storage (e.g. activate 40’s and Jet)

• Accounts for typicality• Creates defaults• Resistant to faulty input

Distributed representation

vanilla

chocolate

strawberry

coffee

vanilla

chocolate

strawberry

coffee

rocky road

tutti-fruitti

Local representation Distributed representation

Local = one node, one conceptDistributed = concepts distributed across multiple nodes

Architecture

Input

Output

Hidden

These models are frequently called Parallel Distributed Processing (or PDP) models

Advantages

PDP models have all the advantages of local representation models, plus:1) Graceful degradation2) Also seeks to show how memories are acquired, not just how they are organized after learning.3) Automatically finds prototypes and exceptions to prototypes4) Automatically generalizes

Is that everything in memory?

Until 20 years ago, the answer would have been “yup.”Today, most memory researchers believe that there are a number of memory systems, at least five of them.

We’ll start with how that idea got started. . .

Patient HM

• Retrieval from LTM intact

• STM intact

• Ability to get material from STM to LTM (i.e. ability to learn) devastated

Pursuit rotor, mirror tracing

HM is shown to learn a new motor skills.

Motor skill demo

More amnesics tested, more tasks learned

Conclusion from this work:

It’s not just that there is memory and there are motor skills: perceptual stuff can be preserved.

People start to think of amnesia as memory minus some process; this missing process impairs most memory, but certain tasks don’t depend on the missing process, so the tasks are learned.

What is the missing process?

• Poor encoding

• Fast forgetting

• Poor retrieval

People give up

Researchers gave up on the idea that there is a single memory system, which is missing some process, leading to the pattern of spared and impaired memory functions.

Instead they concluded that there are multiple memory systems: each in a different part of the brain, learning different things.

Memory systems

• Declarative memory--recall, recog.

Memory systems

• Declarative memory--recall, recog.

• Repetition Priming--gollin figures (like the elephant)

Other priming tasks:

Stem completion priming

WindowReasonAnimalToaster

. ..

Filler taskRea___Acc___Win___

List reading Delay Stem completion

Other priming tasks:

Lexical decision priming

WindowReasonAnimalToaster

. ..

Filler task ReasonRollarpJustice

List reading Delay Lexical decision test

Set display time

Flash words on screen, (masked so iconic memory is foiled) at fastest time that yields 50% correct

Memory systems

• Declarative memory--recall, recog.

• Repetition Priming--gollin figures (like the elephant) and others.

• Motor skill learning--e.g. pursuit rotor

Memory systems

• Declarative memory--recall, recog.

• Repetition Priming--gollin figures (like the elephant)

• Motor skill learning--e.g. pursuit rotor

• Skeletal conditioning--e.g., eyeblink conditioning

Classical conditioning--reminder

If Unconditioned Stimulus--> Unconditioned Response (meat powder) (salivation)

then pair

Conditioned stimulus with the unconditioned stimulus (bell) (meat powder)

then eventually

Conditioned stimulus--> conditioned response(bell) (~salivation)

Skeletal conditioning=an overt response of motor system

If Unconditioned Stimulus--> Unconditioned Response (air puff to cornea) (blinking)

then pair

Conditioned stimulus with the unconditioned stimulus (tone) (air puff to eye)

then eventually

Conditioned stimulus--> conditioned response(bell) (~blinking)

Emotional conditioning = the cs is an emotion

If Unconditioned Stimulus--> Unconditioned Response (boat horn) (anxiety)

then pair

Conditioned stimulus with the unconditioned stimulus (picture of flower) (boat horn)

then eventually

Conditioned stimulus--> conditioned response(picture of flower) (~anxiety)

Memory systems• Declarative memory--recall, recog.

• Repetition Priming--gollin figures (like the elephant)

• Motor skill learning--e.g. pursuit rotor

• Skeletal conditioning--e.g., eyeblink

• Emotional conditioning--emotional resp. to previously neutral stimulus

VERY important source of evidence for separability is the brain basis of these types of learning

hippocampus

Declarative memoryRepetition PrimingMotor skill learningSkeletal conditioning Emotional conditioning

Visual cortex

Declarative memoryRepetition PrimingMotor skill learningSkeletal conditioning Emotional conditioning

Basal ganglia

Declarative memoryRepetition PrimingMotor skill learningSkeletal conditioning Emotional conditioning

Cerebellum

Declarative memoryRepetition PrimingMotor skill learningSkeletal conditioning Emotional conditioning

Declarative memoryRepetition PrimingMotor skill learningSkeletal conditioningEmotional conditioning

Amygdala

Multiple memory systems

This research has expanded our notion of memory. There appear to be

multiple cognitive systems in the brain that have some plasticity.