Title: PSY 368 Human Memory
1PSY 368 Human Memory
2Experiment 2
- Signal Detection (Download details from BB)
- Like last time, find 3 participants
- Youll need index cards for the words (write one
word per card) - Read instructions to participants, the IV is
manipulated with different instructions for each
condition, so make sure that you read the correct
instructions. Youll need to print out 3 copies
of the memory test (1 for each participant) - Fill out the datasheet and bring it to class on
Monday (March 5th, date in assignment is old Fall
date). I will compile data for whole class and
bring it on Wednesday March 7th - Reports will be due the Wednesday after Spring
Break (March 21st),
3Experiment 1 results
- Overall (N 18)
- Immediate 7.6 items
- Delayed 6.0
- Distraction 3.5
- General report comments
- Dont identify your participants
- Stick to APA style as much as you can
- Include your datasheet
4How does Recognition work?
- Two classes of theories
- Single process theories - retrieval is one
process regardless of task - Tagging Model (Yntema Trask, 1963)
- Strength Theory (Wickelgren Norman, 1966)
- Dual process theories - two processes needed for
retrieval - can be task dependent - Generate-recognize model (G-R)
- e.g., Anderson Bower (1972)s HAM
- Remember/Know processes model (R/K)
5Dual-process theories
- Generate-recognize model (G-R)
- Recall is made up of two processes
- First, generate a set of plausible candidates for
recall (Generation stage) - Second, confirm whether each word is worthy of
being recalled (Recognition stage not the same
as the recognition test) - Recognition is made up of only one process
- Because the experimenter provides a candidate,
recognition does not need the generation stage
6Dual-process theories
Remember versus Know Process Model
- (Tulving, 1985 Gardiner, 1988)
- Relatively recent change in recognition
methodology - When you recognize something, do you
- Specifically remember (linked to Episodic memory)
- Conscious recollection of the informations
occurrence at study - Just somehow know (linked to Semantic memory)
- Knowing that it was on the list, but not having
the conscious recollection, just a feeling of
knowing
7Dual-process theories
Remember versus Know Process Model
- Tulving (1985)
- Present subjects with 27 category-member pairs
(FRUIT pear) - Recall tests
- Free recall test
- Cued recall test (category) FRUIT
- Cued recall test (category first letter of
target) FRUIT- p - Results
- The proportion of remember judgments decreased
over the three kinds of tests
Prob(remember) 0.88 0.75 0.48
8Dual-process theories
Remember versus Know Process Model
Gardiner et al (1990, 1991, 1993)
- Remember/Know processes
- Make R/K judgment for Old items
- Remember consciously recollect details of the
items presentation - Know sure an item was presented, but cant
recall any of the details of presentation
- Picture superiority effect
- R P gt W
- K W gt P
- Generation effect
- R G gt R
- K R G
- Word frequency effect
- R L gt H
- K H L
9Remember Versus Know
Remember versus Know Process Model
Gardiner et al (1990, 1991, 1993) gives an
explanation
- Remember judgments are influenced by conceptual
and attentional factors - Know judgments are based on a procedural memory
system - This is similar to a distinction between explicit
and implicit memory (more on this next week)
10Techniques used to distinguish dual processes
- Signal Detection Theory
- A technique for separating discrimination (true
detection) from response bias - Process Dissociation (next week)
- A technique for separating intentional
(effortful) retrieval processes from incidental
(automatic) retrieval processes - May want to go back and review pages 111-114
11Signal Detection Theory
- Signal Detection Theory
- A model for explaining recognition memory
- Based on auditory perception experiments
- Typical Task
- Ask participants to detect a faint tone (signal)
presented against a background of noise - The tones loudness against the background noise
is manipulated
Volume
Background Noise
Easy-to-DetectSignal
Hard-to-DetectSignal
12Signal Detection Theory
- Brief History
- In World War II radar waves were used to detect
enemy aircraft. - The soldiers had to determine if the little spots
of light are enemies, or simple noise (I.e.
birds). - There was no clearly defined criteria for making
these kinds of decisions.
SIGNAL Are the spots on the screen enemies?
- Consequences
- If an enemy went undetected, people could be
killed. - If noise was interpreted as an enemy, time and
money would be lost and people would be put in
harms way
yes
no
DECISION Should you scramble the jets?
Hit False alarm
Miss Correct reject
yes
no
13Signal Detection Theory
- Response bias is based on a participants
preference for a particular outcome. - Preferences are based on costs rewards
- For example,
- People will die because I failed to detect enemy,
that is a very high cost. - If congress yells at me for spending money, that
is not a very high cost.
SIGNAL Are the spots on the screen enemies?
yes
no
DECISION Should you scramble the jets?
Hit False alarm
Miss Correct reject
yes
no
14Signal Detection Theory
- Criterion level (C or ß) is set based on outcome
preferences. - Criterion level The intensity at which a signal
will be reported as being present (Not the
intensity at which it is perceived).
- High Criterion less hits but also less false
alarms - Low criterion more hits but also more false
alarms
SIGNAL Are the spots on the screen enemies?
yes
no
DECISION Should you scramble the jets?
Hit False alarm
Miss Correct reject
yes
no
15Signal Detection Theory
- Criterion level (C or ß) is set based on outcome
preferences. - Criterion level The intensity at which a signal
will be reported as being present (Not the
intensity at which it is perceived).
- High Criterion less hits but also less false
alarms - Low criterion more hits but also more false
alarms
- Criterion
No alert
Call for jets
16Signal Detection Theory
- d (Dee-prime) Discriminability
- The difference between the means
Low d
- If d is low, then this means there is low
discriminability. - The noise and stimulus are highly overlapping.
- d 0 pure chance
- If d is high, then this means there is high
discriminability. - d 1 moderate performance
- d 4.65 optimal (corresponds to hit
rate0.99, false alarm rate0.01)
high d
17Signal Detection Theory
- Recognition accuracy depends on
- Whether a signal (noise/target memory) was
actually presented - The participants response
- Thus, there are four possible outcomes
- Hits
- Correctly reporting the presence of the signal
- Correct Rejections
- Correctly reporting the absence of the signal
- False Alarms
- Incorrectly reporting presence of the signal when
it did not occur - Misses
- Failing to report the presence of the signal when
it occurred
CORRECT
INCORRECT
18Signal Detection Theory
- Assumptions
- Memory traces have strength values (i.e.
activation levels) - Activation levels dictate how familiar a
stimulus feels - Traces vary in terms of their familiarity, based
on - Attention paid to the stimulus during encoding
- The number of repetitions
- Familiarity values for old and new items are
each normally distributed - On average, new items are less familiar than
old items - However, some distractors are quite familiar
because they appear often in other contexts or
are similar to old items - Thus, there can be overlap between the
distributions - Items that surpass a threshold (i.e. response
criterion) of familiarity are judged old
19Signal Detection Theory
- Everything more familiar than (to the right of)
the response criterion (beta or ß) will be judged
old - A centrally placed ß is unbiased
- Everything less familiar (i.e. to the left of ß)
will be judged new. - Hits (in green)
- Misses (in red)
- Above, the same distribution with the focus on
the lure distribution to highlight - Correct rejections (in green)
- False alarms (in red)
- D prime (d) represents
- The distance between the distributions
- The participants ability to discriminate the two
distributions
20Signal Detection Theory
- A more liberal guesser will
- Have a response criterion shifted to the left
- Accept more targets as old (i.e. hits)
- Accept more lures as old (i.e. false alarms)
- A more conservative guesser will
- Shift ß to the right
- Have fewer hits
- Have fewer false alarms
- Thus, the overlap in the distribution leads to
- Trade offs between hits and false alarms
- Depends on the placement of the response criterion
21Signal Detection Theory
- Calculating d and C (or ß)
- Discriminability (d)
- Step 1) Look up the z-score for the average Hit
and False Alarm rates. - Step 2) Apply the formula d zHIT zFA, where
zFA is the z-score for FAs and zHIT is the
z-score for Hits. - Criteria C (or ß)
- Take the negative of the average of zHIT and zFA.
This is the criterion value C. - Remember that positive C values indicate a
conservative response bias, while negative C
values indicate a liberal response bias. - We will go over this in class again next week
when we have our data for Experiment 2 - http//memory.psych.mun.ca/models/dprime/
22Face Recognition
- Special recognition ability
23Face Recognition
- Evidence for special ability
- Prosopagnosia
- The inability to recognize previously seen faces,
with relative sparing of other perceptual,
cognitive and memory functions. - Intact ability to identify people using nonfacial
features (voice) - Due to brain injury (typically to the right
temporal lobe) - Broad Subtypes
- 1. Apperceptive - failure to generate a
sufficiently accurate percept to allow a
successful match to stores of previously seen
faces. - 2. Associative - accurate percept, but failure to
match because of loss of facial memory stores or
disconnection from them.
24Face Recognition
- Evidence for special ability
- (2) Newborn preferences
- Studies done by Fantz (1961, 1963) - had kids
look at three kinds of figures - Morton and Johnson (1991) report that new-born
babies will preferentially view faces
25Face Recognition
- Evidence for special ability
- (3) Face inversion effect
- Yin (1969) found that whilst people are generally
better at recognising upright faces than they are
other objects. They are worse for inverted faces
than they are for other inverted objects.
- This suggests that the processing underlying
normal face recognition is different from those
underlying object recognition.
26The Thatcher Illusion
(Thomson, 1980)
27The Thatcher Illusion
(Thomson, 1980)
28Why does the Thatcher illusion occur?
- Bartlett and Searcy (1993) conducted experiments
to measure face grotesqueness. - Their results supported the configural
processing hypothesis - i.e. We have a difficulty in understanding the
configuration of features when faces are
inverted. - We arent aware of the odd configuration of
elements within the inverted Thatcher image.
29Face Recognition
- Evidence for special ability
- (4) Pop-out effect for faces (Herschler
Hochstein, 2005)
Find the human face in the display as fast as you
can. Ready?
30Face Recognition
Find the human face in the display as fast as you
can. Ready?
31Face Recognition
- Evidence for special ability
- (4) Pop-out effect for faces (Herschler
Hochstein, 2005)
Now find the animal face. Ready?
32Face Recognition
33Summary
- Recognition is an explicit memory test.
- Single- and dual-process theories of recognition
- Single-process cant account for differences
across recall and recognition - G-R theory cant account for items that are
recalled, but not recognized - Face recognition seems to be a special ability
34The Mirror Effect
- Observed when The type of stimulus that is
accurately recognized as old when old is also
accurately recognized as new when new. The type
that is poorly recognized as old when old is also
poorly recognized as new when new. (Glanzer
Adams, 1985, p.8) - Pervasive in recognition tests
- High/low word frequency and hit/false alarm
rates, presentation rate, age of subject, ...
35The Mirror Effect - Example
The Mirror Effect and the Word Frequency Effect The Mirror Effect and the Word Frequency Effect The Mirror Effect and the Word Frequency Effect
Word Frequency Word Frequency
High Low
Hits 27.84 31.00
False Alarms 10.20 7.63
Source Human Memory, p. 214 Source Human Memory, p. 214 Source Human Memory, p. 214
36The Mirror Effect
- Significance It eliminates all theories of
recognition based on a unidimensional conception
of strength or familiarity (single process
models) - May be able to be explained by dual process
models - Explanations for the mirror effect are still
being formed
37Dual-process theories
Dissociating Recollection and Familiarity
- Process Dissociation Procedure (Jacoby, 1991)
- Task
- Participants study two sets of items in different
contexts - Two different recognition tests follow
- Inclusion Condition
- Say yes if they recognize an item from either
context - Correct recognition Recollection Familiarity
- Exclusion Condition
- Say yes only if they recognize an item from one
of the two contexts - Familiarity False alarms in exclusion condition
- Recollection Inclusions correct recognition
minus Familiarity