Langston,
Cognitive Psychology, Notes 5 -- Imagery
Note: For a lot of this I relied on a very nice essay by Bruce
(1996). Her edited volume Unsolved Mysteries of the Mind
doesn't
really play up the mystery part as much as you'd expect, but it
presents
a nice discussion of some of the debates in Cognitive Psychology.
I. Goals.
A. Where we are/themes.
B. Measuring imagery.
C. Images and memory.
D. Using images.
E. Structure of images.
F. Other kinds of images.
G. Reality monitoring.
II. Where we are/themes. It's hard to fit imagery
into the course as a separate unit since it goes with so many other
areas.
I'm leaving it separate because going over how imagery interacts with
the
other systems will serve as a good review. Basically, our
questions
are:
- What is a mental image?
- What do mental images do for you?
Here's a little exercise (from Bruce, 1996). Imagine a dinner
plate.
There's some spaghetti around the top rim. Just below that are
two
fried eggs side by side. In the middle is a carrot, pointing
down.
Below the carrot is a banana. How many people have a clear mental
image? What do you see there?
Do people use images? This is a perfect cognitive psychology
question. It's the ultimate kind of mental event. Note that
demonstrating that people do use images puts all of our methodology to
the test.
On the surface, it's obvious that imagery exists. Here's a simple
example from Descartes. Imagine a hexagon and a pentagon.
Can
you mentally see the difference between the two? Now, imagine a
999
sided polygon and a 1000 sided polygon. Can you see that?
You
can conceive of such things, but you can't image them, suggesting that
imagery is something different from language and other thought
processes.
Some big debates:
A. Can you have imageless thought? Is it possible to have
a thought not accompanied by a visual, verbal, or tactile image?
Does it matter?
B. What is a visual image? Is it a picture in the
head?
Activation of neural circuits used for vision? Something else?
C. How do you know what's real? We'll finally tackle some
issues raised in the first lecture by asking how you know you're
remembering
an image and not something that actually happened.
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III. Measuring imagery. Most models of intelligence
acknowledge that there are multiple intelligences. You can be
verbally
strong, but spatially weak, and vice versa. In other words,
knowing
a person's verbal ability doesn't necessarily tell you anything about
their
spatial ability.
How can we assess your imagery? There are lots of tasks.
Here are three sampled from a book on intelligence by Guilford (1967).
A. Cube folding. I have some expanded cubes with
arrows.
Mentally fold the cubes and tell me if the arrows will touch.
B. Cube task. I show you the initial picture of an ‘X’
on a cube. Then, I take away the cube and tell you how the X
moves.
You tell me where it ended up.
Demonstration: There are two:
1. Cube folding. Will the arrows touch? The first
is “yes,” the second is “no.” I have some you can fold if you
want
to check.
2. Cube: Here's a cube. Here are the moves:
One down, one back, one down, one left, one back, one right, one up,
one
forward, one forward, one up. Where is it?
What can we learn from these types of tasks? Just like digit
span can tell us about short term memory capacity, this can tell us
about your spatial ability. There seems to
be a lot more variability in spatial ability than verbal ability (in
college
populations). Why? Think about the skills emphasized and
the
tests used for admissions.
Note the parallel to working memory. All of these tasks require
storage plus processing.
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IV. Images and memory.
A. Learning pictures.
1. Shepard (1967): People saw a long list of pictures or
words (612). After two hours, they took a recognition test (two
alternative
forced choice). People were nearly 100% accurate for pictures,
about
88% for words. After a week, people were about 88% for
both.
So, picture memory is better than word memory, but not after a long
delay.
2. Standing (1977): Learn 1000 words, 1000 simple pictures,
and 1000 bizarre pictures. Recognition was tested two days
later.
People learned 615 words, 770 pictures, and 880 bizarre pictures.
So, people are really good with pictures, and better than with
words.
This is part of the evidence that will lead Paivio to propose a dual
code
(one verbal one visual). We'll see that later.
B. Using imagery to learn other stuff.
1. The concrete-abstract dimension. Words vary on a lot
of characteristics. One is how concrete the word is (“computer”
vs.
“thought”). What effect does concreteness have on memory?
Concrete
words are easier to recall than abstract words. I have a
demonstration
of this.
Demonstration: Here's a list of pairs. Some are
pairs of concrete words, some are pairs of abstract words. Learn
them, cued recall. Should remember more concrete words.
Why? Paivio thinks it's a dual code thing. You have a
picture
code that's separate in memory from your word codes. When you get
a concrete word, you can get an image in the picture code, that gives
you
two chances to recall. If you get an abstract word, you only get
one chance to recall (verbal code) and that makes it more likely that
you
will forget. This dual code also explains why picture memory is
better
than word memory. Two codes = twice the chances to find what
you're
looking for.
One source of evidence for dual codes is the symbolic distance
effect.
The basic effect is that it is harder to make decisions about the
relative
orderings of things the closer they are along a dimension. For
example,
think of a flea, a fly, a rabbit, a German Shepard, and a horse.
People's response times to decide which is larger are faster for
comparisons
like horse and flea than for comparisons like fly and flea. The
closer
the objects are, the harder it is to decide. This is best
explained
as an image thing. People access a mental representation that is
an analog of the real thing, compare it to another image, and “see” the
result.
One source of evidence for Paivio is that picture symbolic distance
tasks are faster than verbal symbolic distance tasks. The picture
can access the correct mental system directly, the verbal task has to
be
recoded before a comparison can be made, making pictures faster.
Note that on one hand a symbolic distance effect is kind of nuts.
If I describe an ordering to you that includes the sentence “the fly is
larger than the flea” and then ask you to verify the statement “the fly
is larger than the flea” it takes you longer than a statement about the
fly and a horse even though it's the exact same sentence. That
would
lead some to say that verbal and image systems are clearly separate.
C. Putting imagery to work. Mnemonic devices (memory
tricks)
usually take advantage of imagery. A popular one is
peg-words.
You first memorize a list that goes from one to ten (one is a horse,
two
is a picture, ...). Then, when you have a new list to learn (like
your shopping list) you imagine the items on the list interacting with
your peg words. So, if you need to buy a toothbrush, you might
imagine
a horse brushing his teeth. When you get to the store, you start
in “one is a horse” and that triggers the memory of the image, and you
buy a toothbrush.
Demonstration: I'll hand out some peg-word systems.
Practice until you've completely learned your system. Here are
the
three systems:
| One is a bun |
One is a door |
One is truth |
| Two is a shoe |
Two is heaven |
Two is data |
| Three is a tree |
Three is a gate |
Three is a message |
| Four is a door |
Four is sticks |
Four is love |
| Five is a hive |
Five is a hen |
Five is knowledge |
| Six is sticks |
Six is a bun |
Six is fun |
| Seven is heaven |
Seven is a tree |
Seven is time |
| Eight is a gate |
Eight is a hive |
Eight is have |
| Nine is a line |
Nine is a shoe |
Nine is beauty |
| Ten is a hen |
Ten is a line |
Ten is focus |
Then, memorize the shopping list. Then recall. Compare.
One should be best, followed by two, followed by three.
Why?
One has rhyming plus imagery (the words are all concrete). Two
has
imagery, but no rhyming. Three has neither. By the way, one
is the real peg-word system if you
want
to use it.
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V. Using images. Now we come to the real
problem.
I can't see you having an image. So, the data I'm about to
present
are based on a great deal of trust that participants are really doing
it.
The basic question is to look at the relationship between pictures and
images.
A. Mental rotation. If you physically rotate something
on a table, the farther you go, the longer it takes. Do images
work
this way?
CogLab: Mental
rotation exercise.
It should work. Shepard has found this effect in a number of
studies. The farther you rotate, the longer it takes, and the
relationship
is pretty linear.
B. Scanning. If I ask you to visually scan from one spot
to another, the farther you go, the longer it takes. Kosslyn had
people memorize an island, and he found a linear relationship between
distance
and time.
Another experiment manipulated instruction set (Kosslyn, 1976).
Some people were instructed to use images to help answer questions,
others
had no instructions. Imagery people were faster to answer
questions
if the size of the item probed was larger (does a bee have
wings).
Non-imagery people were faster on the basis of association strength
(does
a bee have a stinger). So, focusing on images seems to access a
different
kind of information.
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VI. Structure of images. What is an image?
Phenomenologically, what does it feel like? What might it
be?
Again, since we can't see it, this is entirely speculative. But,
here are two options:
A. Images are propositions. A proposition is an idea
unit.
It's basically verbal in nature, but it isn't words or
linguistic.
It's a kind of language of thought. So, images feel like
pictures,
but they're really coded in a different kind of language. The
feeling
isn't real.
B. Images are pictures. Sort of like what we've been
building
so far. On one level, this is absurd. A tomato is
red.
A picture of a tomato is red. Is an image of a tomato red?
No. Is an image of an elephant physically larger than an image of
a rabbit? Some of the scanning stuff certainly suggests this
(“think
of a rabbit by a fly, think of his eyelash” is easier than “think of a
rabbit by an elephant, think of his eyelash”).
C. How can we tell if an image is like a picture? Well,
we could look for cases where pictures and images are different.
Let's try some of that.
1. It's hard to reverse an image, it's easy to reverse a
picture.
Look at the drawings below:
The one on the left could be a rabbit or a duck. You should be
able to see it both ways. The cube on the right can flip which
face
is the front. Again, you should be able to see it both
ways.
Now, get an image, hide the paper, and try to flip it. It should
be hard, and you might not be able to do it. So, images and
pictures
do differ.
2. It's hard to decompose an image. Try the demonstration.
Demonstration: Are images like a picture in the
head?
If so, then activities that a picture can support should also be
supported
by an image. Let's see (based on Reed and Johnsen, 1975).
I'm going to show you a figure. Memorize it and get a clear
mental
image. When you're ready, raise your hand. Now, I'll cover
it up and ask you if certain shapes are part of the figure. Write
down the letters of all of the shapes that are in the figure.
Show
that people are usually bad.
Let's try number two. Bad again.
Most people make a lot of mistakes. Again, images and pictures
are different.
However, Finke, Pinker, and Farah (1989) argue that image
reinterpretation
is possible, it just depends on the kind of processing.
Overcoming
low-level grouping information is hard, higher level organization
should
be possible. An example: Think of a lower-case k.
Now,
imagine a circle around the k, just not touching it. Now, cut off
the lower half of the k. What do you have? A lot of people
can do this sort of thing. The rabbit and reinterpretation
demonstrations
are a different sort of processing.
D. Maybe images use perceptual hardware (it's like seeing, only
fainter). So, an image is basically utilizing the same hardware
that
you use for perception. This makes it qualitatively and
phenomenologically
different from processing verbal information, but still ties it to a
realistic
neurological foundation.
1. We can start by looking at interference. This is popular
with cognitive psychologists. If images use visual hardware and
words
use verbal hardware, pictures and words shouldn't interfere. If
they
all use the same hardware, pictures and words should interfere with
each
other. Try the demonstration.
Demonstration: Are images really verbally coded (like
propositions)? We should get different patterns of interference
if
images and verbal codes are different. Let's try (this is based
on
Brooks, 1968). I have some letters. The task is to go from
the first corner around the letter clockwise. At each corner,
tell
me “yes” if it's an outside corner and “no” if it's an inside
corner.
You will respond based on a mental image.
There are two response modalities, visual and verbal. If I assign
you to verbal, you whisper your “yes” and “no” answers. If you're
visual, you look at the ‘Y’ or ‘N’ on the correct row depending on what
corner you're on. If images are visual, visual responders should
be slower (more interference). To let us know, I'll split the
class
in half. Clap when you're done. The verbal half of the room
should clap first.
Now, let's look at verbal codes. I have some sentences.
For each word, respond “yes” if it's a noun or pronoun, “no”
otherwise.
We'll have the two modalities again. In this case, the verbal
modality
should be interfered with.
We should get more interference between pictures and pictures than
pictures and words and vice versa. So, they seem to use different
hardware. More importantly, it's a case where images and
perceptual
mechanisms seem to share resources.
2. Finke and Kosslyn (1980) measured acuity in visual and
imagined
fields and found the same elliptical visual fields in both
domains.
In both cases, better acuity was below the horizontal axis than
above.
The findings were not consistent with people's beliefs about their
imaginal
visual fields, suggesting that the results weren't due to demand
characteristics.
Spatial frequency resolution also followed this pattern (Finke &
Kurtzman,
1981). These results suggest a similarity between visual
perception
and imagery.
3. Imagery doesn't seem to produce after-effects like vision
does. For example, staring at red bars and then looking at a
white
background will cause you to perceive faint green bars. Imagining
red bars will produce no such after-effect (maybe?).
4. Imagery also doesn't seem to lead to repetition priming
effects.
For example, imagining words in lower case doesn't seem to improve
perception
of those words. This is a relatively new area of research, so
maybe
something will emerge here.
5. Imagery supports high level redescription, but not low level
grouping (see above). Vision supports both.
E. The conclusion: It will be hard for us to tell what
images are using purely cognitive methods.
One approach to solving the imagery debate (the “what are images”
question)
comes from neuropsychology. You can get a look at a person's
brain
as they form a mental image vs. do a verbal task. Are the same
parts
of the brain involved in the two tasks? Do images actually use
visual
cortex like perception? It's sort of a mix between cognitive
approaches
and neurological approaches.
Another possible resolution may come from additional interference
experiments.
Basically, if you tie up the parts of the perceptual system that
perceive
a particular kind of stimulus, that should hurt imagery as well.
If you get a consistent pattern of this kind of result, it would
suggest
a relationship between imaginal and perceptual systems.
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VII. Other kinds of images. I've been acting like
visual images are all there are. Obviously, that's wrong.
Can
you imagine the smell of leaves burning? Can you imagine the
taste
of a steak? Do you hear an inner voice? (Uh-oh.)
Just a taste of this. Smith, Reisberg, and Wilson (1992) had
people reinterpret strings like “NE1 4 10S” as “anyone for tennis,” but
silently. People could interpret 73% of the strings in a quiet
room.
With auditory distraction, they could do 40%. With articulatory
suppression,
21%. In other words, the more you engaged the vocal hardware, the
worse their inner voice imagery got.
This area is rich in WRR opportunities.
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VIII. Reality monitoring. Have you ever had a dream
that you later confused with a real experience? (Uh-oh.) Do
you sometimes experience déjà vu? Have you ever
remembered
something that didn't really happen? These are all problems with
reality monitoring. How do you distinguish imagined events from
real
ones, especially if they use the same neural hardware, as we've been
discussing
above?
The basic answer is a process of summing up perceptual information
and information about cognitive activity associated with the memory,
and
comparing the two. A lot of cognitive with little perceptual is
probably
imagined. A lot of perceptual and some cognitive is probably
real.
Test? Johnson, Foley, and Leach (1988) had people imagine words
being spoken by someone else (whose voice they were familiar with) and
then had that person read some words out loud. This caused more
confusion
than imagining words in their own voice or some other person's
voice.
In other words, changing the balance between perceptual information and
internal information made discriminating between real and imagined
harder.
Finke, Johnson, and Shyi (1988) showed that the less attention you
pay when you're creating images (or the less work you do), the harder
it
is to separate imagination from reality. People had to complete
shapes
like the following:
When the shapes were letters and numbers, it was hard to tell which
had been seen whole and which were imagined whole. When the
shapes
were novel (taking more effort to complete) people were pretty good at
the task.
Brain-wise, two parts are implicated in reality monitoring.
People
with frontal lobe damage have trouble with confabulation of “memories”
that are false. It is difficult or impossible to persuade them
that
those events did not occur. People who have their temporal lobes
stimulated tend to experience déjà vu. It appears
to
arise as a result of reality monitoring, but the exact mechanism is
unclear.
That should just about clear everything up on the déjà vu
front (he says, tongue-in-cheek).
(This is a great section for a WRR. Some WRRs I've had for this
topic: McNally, R.J., & Kohlbeck, P.A. (19
).
Reality monitoring in obsessive compulsive disorder. Behavior
Research
and Theory, 31, 249-253; Anderson, R. (1984). Did I do it
or
did I only imagine doing it?)
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Cognitive Psychology Notes 5
Will Langston
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