Visual Imagery and
Perception
Miri Besken
PSYC200
Plan
• Visual imagery
• Debates about imagery
• Spatial vs propositional
• Similarities & interactions with perception
• Behavioral studies
• Imagery and the brain
What Is Imagery?
• Mental imagery: experiencing a sensory impression in the absence
of sensory input
• Visual imagery: “seeing” in the absence of a visual stimulus
• Auditory imagery: “Hearing’ in the absence of an auditory stimulus
Visual Imagery in Everyday Life
• Adds to verbal techniques
• Helps organization of thoughts
• Helps memory
• Facilitates actions that require visual
History
• Paivio’s paired associates paradigm
• Imageless thought debate
Paired-Associates Paradigm
• Paivio discovered that concrete words are remembered more than
abstract words.
• Conceptual peg hypothesis: Concrete nouns create images that other
words can hang onto
Mental Chrnometry
Mental Chronometry
• Mental rotation takes more time as the angle is more separated from
the original figure, so imagery is spatial (Shepard & Metzler, 1971)
Imagery and Perception: Do they share the same
mechanisms
• Spatial correspondence between imagery and perception
• Mental scanning: We act as if our mental images are physical entities
• When participants create images in their minds, the results are usually
similar to what one would expect when they perceive the image
Is visual imagery spatial?
Kosslyn (1973)
Memorize picture, create an
image of it
In image, move from one part of
the picture to another
It took longer for
participants to mentally
move long distances than
shorter distances
Lea (1975)
What if people are distracted
by the other objects in the
middle?
Is visual imagery spatial?
• Kosslyn et al. (1978)
– Island with 7 locations, 21 trips
– It took longer to scan between greater distances
– Visual imagery is spatial
Is Imagery Spatial or Propositional
VS
KOSSLYN
PYLYSHYN
Is Imagery Spatial or Propositional
IMAGERY IS SPATIAL
• Can be represented by pictures
• Representations are spatial in
nature
• The image corresponds to specific
VS
locations in space
KOSSLYN
IMAGERY IS PROPOSITIONAL
• Can be represented by
abstract symbols
• Representations are
propositional
• Experience that we have is a
epiphenomenon
PYLYSHYN
Is Imagery Spatial or Propositional
VS
KOSSLYN
PYLYSHYN
Is Imagery Spatial or Propositional
Is Imagery Spatial or Propositional
Pylyshyn
When asked to
imagine something,
people ask
themselves what t
would look like to see
it and then simulate
as many aspects of
this event as they
can.
Tacid Knowledge
explanation - We use
our real world
knowledge to make
judgments.
Is Imagery Spatial or Propositional
 Participants judge whether
arrow points to dots previously
seen
 Longer reaction time when
greater distance between arrow
and dot (as if they were mentally
“traveling”)
 Not instructed to use visual
imagery
 No time to memorize, no tacit
knowledge (participants have
world knowledge about the dots
in the experiment)
Comparing Imagery and Perception: Size in the
Visual Field
Imagination of different sized animals
Mental Walk Task
 Imagine that you are walking
towards an “______” and an
“_____”. You stop at a point
when the large animal
overflows your visual field.
 Elephant and rabbit
 Rabbit and mosquito
 “Does the rabbit have
whiskers?”
 RT to this question is different
depending on whether rabbit is
the larger or the smaller animal
in the scene.
“does the rabbit have
whiskers? ”
Comparing Imagery and Perception:
Perception and Imagery Interactions
 If perception affects imagery
and imagery affects perception,
this means that they have
access to the same
mechanisms.
 “imagine a banana”
 Dim image of the banana
projected on the screen,
unbeknownst to the subject
 All subjects described the
image on the screen
 None noticed that there was an
image projected.
Comparing Imagery and Perception:
Perception and Imagery Interactions
“imagine H”
“Tell me whether
the letter was
presented on the
first or the second
slide. ”
“Performance
better when the
imagined letter
and the projected
letter are the
same”
Imagery: Resolving the Conflict
• Paired associated paradigm
• Could be spatial
• Mental rotation
• Mental scanning
• Mental walk
• Could be propositional
• Almost of the experiments can be
explained by using worldknowledge
• Difficult to tell in between real
and imagined objects
• Imagery helps perception
• Debate might be resolved with
neuropsyhological studies and
brain imaging
Imagery Neurons- Similarities between
perception and imagery Kreiman (2000)
• Single cell recording
• Neurons that respond to baseball,
and not to a face
• Responds to both
• Perceptual input
• Imagery
• Imagery neurons
• Medial temporal lobe
Brain Imaging- Similarities between
perception and imagery
LeBihan et al (1993)
 Increased activity striate cortex
 Higher activity with perception
as compared to imagery
Goldenberg (1989)
 Higher activity in visual cortex
for questions involving imagery
“Is the green of the trees darker
than the green of the grass” > “is
the intensity of electrical current
measured in amperes”
Brain Imaging- Differences between
perception and imagery
Ganis et al (2004)
1. Study pictures of objects
2. They either:
- Hear the word tree and imagine it
- Look at a faint picture of the tree
3.
Answer “Is it wider than it is
tall”
Brain Imaging- Differences between
perception and imagery
Continued (Ganis et al)
• Same level of activation in frontal
lobe (a) and and further back (b)
• More activation for perception in
occipital lobe (c)
• Why?
Brain Imaging- Similarities between
perception and imagery
Johnson & Johnson (2014)
• Multivoxel pattern analysis
(train a classifier to associate a
particular activation pattern with
an object and then test to see if
the classifier can distinguish
between patterns to identify the
pattern by looking at the
pattern)
Brain Imaging- Similarities between
perception and imagery
Johnson & Johnson (2014)
• Multivoxel pattern analysis for
beach, dessert, field and house
identification
• When participant perceived,
the ability of the classifier to
discriminate is 63% (chance
performance: 50%)
• When the participants
imagined, the ability of the
classifier to discriminate if 55%.
• Transcranial Magnetic Stimulation
(TMS)
• Temporary disruption of the
certain parts of brain through the
usage of a stimulating coil (that
causes a pulsating magnetic area)
TMS – Similarities between perception and
imagery
 Pylyshyn – Brain activity for
imagery is an epiphenomenon
 Kosslyn (2004)
1. TMS applied to visual area
2. Look at the figure on the left
3. Then, they either


4.
Keep on looking
Imagine the figure
Answer questions (e.g. are
the stripes in quadrant2
longer than quadrant 3)
Results: Slower response for both
imagery and perception
Neuropsychological Case Studies- Similarities Between
Perception and Imagery
• Removing part of visual cortex
decreases image size for both
• Perceptual tasks
• Imagery tasks
• Visual cortex is important for
imagery
Neuropsychological Case Studies- Similarities Between
Perception and Imagery
• Unilateral neglect syndrome
• Damage to parietal lobe
• Same problems in mental
walk task as in the perceptual
tasks
Neuropsychological Case Studies- Dissociations Between
Perception and Imagery
• R. M. (damage to occipital and
parietal lobe)
Perception
Imagery
• Recognize and draw when
presented perceptually
• Cannot draw from memory &
cannot answer questions involving
imagery
• C. K.
Patient R.M.
(Farah et al,
1993)
Patient C.K.
(Behrmann et al,
1994)
• Visual agnosia
• Trouble naming objects
• Can draw from memory
So what?
Similarities between perception and
imagery
 Single cells responding to both
perception and imagery
 Same areas are activated for
perception and imagery in brain
imaging
 TMS causes increased RT in both
perception and imagery
 Damages to occipital and parietal
lobe cause problems for both
perception and imagery
 Mental walk in unitaleral neglect
 Overflowing of the image
Dissociations between perception and
imagery
• Perception activates additional areas
in primary visual area compared to
imagery
• Double dissociations in
neuropsychological studies
• Some patients who perceive cannot
imagine
• Some patients who imagine cannot
perceive
Theoretically:
-Perception and imagery overlap only
partially
-Visual perception starts with bottom-up
processing
-Analysis of edges and orientations
-Assembled + prior knowledge applied
-Visual imagery starts as a top-down process
-Preassembled images
-No activation of cortical areas
-For C.K. , upper processing areas (topdown processing) is intact
-For R.M., lower processing (bottom-up
processing) is intact.
Indıvıdual Imagery Dıfferences
https://www.youtube.com/watch?v=KuWSh4n5AiI
• Aphantasia: Inability to have visual images in one’s mind’s eye
• Despite the inability to imagine, these individuals lead typical lives
• Substitute propositional statements to recover for the lack of visual images
• Pylyshyn is claimed to have aphantasia ☺
Indıvıdual Imagery Dıfferences
• Draw a bicycle from your
memory
• Over-estimation of our ability
to imagine
• Imagery may be more related
to memory and semantic
knowledge structures than
thought
Finally,
• Imagery and perception are similar in certain ways and different in
others.
• Brain imaging and neuropsychological case studies show overlaps and
dissociations for both systems
• Imagery is more fragile as compared to perception & requires more
effort