Cognitive ProcessesPSY 334

Chapter 6 – Human Memory: Encoding and Storage

Ebbinghaus

First rigorous investigation of human memory – 1885.Taught himself nonsense syllables

DAX, BUP, LOCSavings – the amount of time needed to relearn a list after it has already been learned and forgotten.Forgetting function – most forgetting takes place right away.

Memory Models

Atkinson & Shiffrin – proposed a three-stage model including:

Sensory store – if attended goes to STMShort-term memory (STM) – if rehearsed goes to LTMLong-term memory (LTM)

No longer the current view of memory.Still presented in some books.

The Three-Stage Model

Environment Sensory store Short-term (working) memory Long-term memory

Responses

Executive control processes

Sensation/perception Attention

encoding

retrieval

Retention Times

Environment Sensory store Short-term (working) memory Long-term memory

encoding

retrieval

1-3 seconds 15-25 seconds 1 sec to a lifetime

Sensory Memory

Holds info when it first comes in.Allows a person to extract meaning from an image or series of sounds.Sperling’s partial report procedure:

A display of three rows of letters is presented.After it is taken away, a tone signals which row to report.Subjects were able to report most letters.

Sperling’s Partial Report

A medium tone signals the subject to report the letters in this row

Sperling’s Results

Delay

Kinds of Sensory Stores

Iconic memory – visualBright postexposure field wipes out memory after 1 sec, dark after 5 sec.

Echoic memory – auditoryLasts up to 10 sec (measured by ERP)

Located in the sensory cortexes.

Short Term Memory

The original idea is that when info in sensory memory is paid attention to, it moves into short term memory.With rehearsal, it then moves into long term memory.STM has limited capacity, called memory span.

Miller’s magic number (7 ± 2)New info pushes out older info (Shepard)

Shepard’s Results

Number of intervening items

Probability of recalling the target item

Criticisms of STM

Rate of forgetting seemed to be quicker than Ebbinghaus’s data, but is not really.Amount of rehearsal appeared to be related to transfer to long-term memory.

Later it was found that the kind of rehearsal matters, not the amount.Passive rehearsal does little to achieve long-term memory.

Information may go directly to LTM.

Depth of Processing

Craik & Lockhart – proposed that it is not how long material is rehearsed but the depth of processing that matters.Levels of processing demo.

Working Memory

Baddeley – in working memory speed of rehearsal determines memory span. Articulatory loop – stores whatever can be processed in a given amount of time.

Word length effect: 4.5 one-syllable words remembered compared to 2.6 long ones.1.5 to 2 seconds material can be kept.Visuopatial sketchpad – rehearses images.Central executive – controls other systems.

Word-Lenth Determines Forgetting

Delayed Matching Task

Delayed Matching to Sample – monkey must recall where food was placed.

Monkeys with lesion to frontal cortex cannot remember food location.Human infants can’t do it until 1 year old.

Regions of frontal cortex fire only during the delay – keeping location in mind.

Different prefrontal regions are used to remember different kinds of information.

Delayed Matching to Sample

Importance of Frontal Cortex

In primates, working memory is localized to the frontal cortex.Delayed matching to sample task:

Monkeys are shown food that is then hidden.Later they are given a chance to locate it.

Monkeys with frontal lobe lesions cannot do this task.

Activation

Activation – how available information is to memory:

Probability of access – how likely you are to remember something.Rate of access – how fast something can be remembered.

From moment to moment, items differ in their degree of activation in memory.

Anderson’s ACT Model

ACT – Adaptive Control of ThoughtMoses Effect -- subjects shown the words Bible, animal and flood should recall Noah but recall Moses instead.

When given the word flood they think of Mississippi or Johnstown but not Noah.

Why? Recall is based on both baseline and activation from associated concepts.

Moses and Jesus have higher baselines.

The ACT Model

Factors Affecting Activation

How recently we have used the memory:

Loftus – manipulated amount of delay1.53 sec first time, then 1.21, 1.28, and 1.33 with 3 items intervening.

How much we have practiced the memory – how frequently it is used.

Anderson’s study (sailor is in the park)

Spreading Activation

Activation spreads along the paths of a propositional network.

Related items are faster to recall.Associative priming – involuntary spread of activation to associated items in memory.

Kaplan’s dissertation – cues to solving riddles hidden in the environment led to faster solutions.

Associative Priming

Meyer & Schvaneveldt – spreading activation affects how quickly words are read.

Subjects judged whether pairs of related & unrelated items were words.Judgments about related words were faster.

Meyer and Schvaneveldt

Practice and Strength

The amount of spreading activation depends on the strength of a memory.Memory strength increases with practice.Greater memory strength increases the likelihood of recall.

Power Function

Each time we use a memory trace, it gradually becomes a little stronger.Power law of learning:

T = 1.40 P-0.24

T is recognition time, P is days of practice.Linear when plotted on log-log scale.

Learning Curves

Practicing Addition Problems

Long Term Potentiation (LTP)

Neural changes may occur with practice:

Long-term potentiation (LTP) in hippocampus.Repeated electrical stimulation of neurons leads to increased sensitivity.

LTP changes are a power function.

Neural Changes Mirror Behavioral Changes

Neural Correlates of Encoding

Better memory occurs for items with stronger brain processing at the time of study:

Words evoking higher ERP signals are better remembered later.Greater frontal activation with deeper processing of verbal information.Greater activation of hippocampus with better long-term memory.

Activation in Prefrontal Cortex

Words activate left prefrontal cortex

Pictures activate right prefrontal cortex

Hemodynamic = blow flow during brain activity

Factors Influencing Memory

Study alone does not improve memory –what matters is how studying is done.

Shallow study results in little improvement.Semantic associates (tulip-flower) better remembered than rhymes (tower-flower), 81% vs 70%.

Better retention occurs for more meaningful elaboration.

Elaborative Processing

Elaboration – embellishing an item with additional information.Anderson & Bower – subjects added details to simple sentences:

57% recall without elaboration72% recall with made-up details added

Self-generated elaborations are better than experimenter-generated ones.

Self-Generated Elaborations

Stein & Bransford – subjects were given 10 sentences. Four conditions:

Just the sentences alone – 4.2 adjectivesSubject generates an elaboration – 5.8Experimenter-generated imprecise elaboration – 2.2Experimenter-generated precise elaboration – 7.8

Precision of detail (constraint) matters, not who generates the elaboration.

Advance Organizers

PQ4R method – use questions to guide reading.

64% correct, compared to 57% (controls)76% of relevant questions correct, 52% of non-relevant.

These study techniques work because they encourage elaboration.

Question making and question answering both improve memory for text (reviewing is better than seeing the questions first).

Meaningful Elaboration

Elaboration need not be meaningful –other sorts of elaboration also work.Kolers compared memory for right-side-up sentences with upside-down.

Extra processing needed to read upside down may enhance memory.

Slamecka & Graf – compared generation of synonyms and rhymes. Both improved memory, but synonyms did more.

Slamecka & Graf’s Results

Mnemonics

Method of Loci – place items in a location, then take a mental walk.Peg-word System – use peg words as a structure and associate a list of items with them using visualization.

Create acronyms for lists of items.Convert nonsense syllables (DAX, GIB) into meaningful items by associating them with real words (e.g., DAD).

“This Old Man” Song

http://www.youtube.com/watch?v=3cYf9vkW_xU

http://www.totlol.com/watch/5d-6Q5V79CM/This-Old-Man/0/

Pegword System1 – bun2 – shoe3 – tree4 – door5 – hive6 – sticks7 – heaven8 – gate9 – wine10 -- hen

Incidental Learning

It does not matter whether people intend to learn something or not.

What matters is how material is processed.Orienting tasks:

Count whether work has e or g.Rate the pleasantness of words.Half of subjects told they would be asked to remember words later, half not told.

No advantage to knowing ahead of time.

Awareness of Learning

Flashbulb Memories

Self-reference effect -- people have better memory for events that are important to them and close friends.Flashbulb memories – recall of traumatic events long after the fact.

Seem vivid but can be very inaccurate.Thatcher’s resignation:

60% memory for UK subjects, 20% non-UK

Self-Reference Effect

Two explanations:People have special mechanisms for encoding info relevant to themselves.Info relevant to the self is rehearsed more often.

High arousal may enhance memory.Memory is better for words related to the self – perhaps due to better elaboration.