Chapter 6 – Human Memory:
Encoding and Storage

Ebbinghaus
 First rigorous investigation of human memory – 1885.
 Taught himself nonsense syllables

 DAX, BUP, LOC
Savings – 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 threestage model including:


Sensory store – if attended goes to STM
Short-term memory (STM) – if rehearsed goes to LTM
 Long-term memory (LTM)
 No longer the current view of memory.
 Still presented in some books.

The Three-Stage Model
Responses
Sensation/perception
Environment
Attention
Sensory store retrieval
Short-term
(working) memory encoding
Long-term memory
Executive control processes

Retention Times
Environment Sensory store retrieval
Short-term
(working) memory encoding
Long-term memory
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 – visual
 Bright postexposure field wipes out memory after 1 sec, dark after 5 sec.
 Echoic memory – auditory
 Lasts 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 & Teghtsoonian’s
Results
Probability of recalling the target item
Number of intervening items

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 can 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.
Visuospatial sketchpad – rehearses images
Central executive – controls other systems.

Word-Length 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

Activation and Long-Term
Memory
 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 Thought
 Subjects shown the word “flood” should recall Noah but do not without “Bible,”
“animal” and “flood” together.
 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.

Moses Illusion
 How many animals of each species did
Moses bring onto the ark?
 People respond 2 rather than none.
 This occurs because people do not focus attention on who did it, and because
Moses and Noah are both Biblical characters.
 This is a semantic illusion.

The ACT Model

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 elaboration
 72% 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 adjectives
 Subject generates an elaboration – 5.8
 Experimenter-generated imprecise elaboration – 2.2
 Experimenter-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-sideup 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 System
1 – bun
2 – shoe
3 – tree
4 – door
5 – hive
6 – sticks
7 – heaven
8 – gate
9 – wine
10 -- 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 word 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, just like everyday memories.
 Thatcher’s resignation:
 60% memory for UK subjects, 20% non-
UK

9/11 Memories
 Talairco & Rubin (2003) found that 9/11 story-consistent details decreased and inconsistent details increased with time.
 Rate and amount of both kinds of details were closely similar for flashbulb & everyday memories.
 Sharot et al. (2007) reported greater activity in the amygdala for people closer to ground zero, when recalling 3 yrs later

Arousal & the Self-Reference
Effect
 Two explanations:
 Activation of the amygdala involves a biological mechanism reinforcing memory for events important to us.
 Info relevant and important to the self is rehearsed more often – resulting in better elaboration.
 High arousal may enhance memory above and beyond rehearsal.