Perception Final Exam
Prof. David J. Heeger
Dec 18, 2006
Read these instructions:
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This exam is closed book, no notes, no index cards.
Turn off your cell phone.
Answer all questions.
For multiple choice questions, mark your answers on the scantron card with a #2
pencil.
For the short answer questions, mark your answers clearly on the answer sheet
provided at the end of this test booklet. Please make an effort to write legibly.
Write your name on the answer sheet pages and on the scantron (1 point).
Turn in the exam as well as the answer sheets.
Part I. Short Answer (4 points each). Write your name and your answers on the
accompanying answer sheet. Be concise (one or two sentences will suffice). If your
answer includes lots of extraneous facts then you will not receive full credit, even if the
extraneous comments are true and even if the correct answer is buried somewhere in
there.
1) We will show you an excerpt from Hubel and Wiesel's film of receptive fields. On
the accompanying answer sheet, list all of the correct descriptors, but none of the
incorrect descriptors (-1 point for each item that is listed incorrectly).
ON-center/OFF-surround receptive field
OFF-center/ON-surround receptive field
simple cell
complex cell
hypercomplex cell
direction selective
orientation selective
2) Connect the name of the primary receiving area with its location (you may use
locations more than once.) 4/3 point each
Visual cortex
(occ)
Frontal lobe
Auditory cortex (temp)
Parietal lobe
Somatosensory cortex(parietal)
Occipital lobe
Temporal lobe
3) We conduct a signal detection experiment on the same subject on two consecutive
days. We find that the false alarm rate changes from day to day on the same wellpracticed subject, even though the strengths of the signal and noise are fixed. What
must also be happening to the hit rate and why? Draw a graph of an ROC curve to
illustrate your answer.
the hit rate should change in the same direction as the false alarm rate. (2 pts)
If sensitivity is the same, it means you’re still on the same d prime curve, simply
changing criterion. (2 pts)
4) Below are four pure tone sound waves and plots of the firing rates of two auditory
nerve fibers in response to each sound wave. Explain how these data provide
evidence for the temporal code theory of pitch perception.
The firing rates are more rapid when the signal is higher frequency (2 pts) and are
phase locked to the signal (2 pts).
5) Michael Posner, a famous cognitive neuroscientist, was once asked what is the main
difference between human brains and other primate (e.g., chimps) brains that has
allowed humans to be so much more successful. His answer was that human brains
have special pathways for very fast neural processing. Which aspect of speech
perception demands fast temporal processing? Explain why language learning
disabilities are linked with deficits in fast processing.
Formant transitions (2 pts)
Children with speech perception impairments have difficulty discriminating rapid
changes in sound (2 pts)
6) When a patient has glaucoma, the usual flow within the aqueous and vitreous
humors is disrupted, changing ocular pressure. How does this change in pressure
disturb the eye, potentially leading to blindness?
Pressure build up can damage the optic nerve, and it can also lead to retinal
detachment or damage the blood vessels at the back of the eye starving the retina of
nourishment.
(4/3 point each)
7) During the second World War pilots wore red goggles while being briefed,
immediately before, a night time mission. During the mission they wore no goggles.
Using what you know about rod and cone wavelength sensitivity, explain (a) why the
pilots wore goggles, and (b) why the goggles only passed long wavelength (650 nm)
light, and not middle- or short-wavelength light.
wore goggles to allow dark adaptation before night mission (2 pts)
red filters out light that the rods would respond to because rods are not sensitive to long
wavelengths and hence won’t get bleached (2 pts)
8) List 2 of the 4 characteristic properties of parallel pathways in the visual and auditory
systems? Use auditory sound localization as an example and explain how parallel
pathways in the auditory system conform to these 2 characteristics.
Physiologically different: some neurons respond to interaural timing differences (MSO),
others to interaural intensity differences (LSO)
Complete coverage: both respond at all frequencies or all parts of auditory environment
surrounding the head
Recombination: signals recombined in colliculus
Anatomically different: different neural loci: LSO vs MSO
(1 pt for each pathway property, 1 pt for correct sound localization example of each
property)
9) How are visual cortical areas defined? List the 4 aspects of visual areas that
differentiate one from another.
Physiology, Architecture, Connections, Topography (1 point each)
Part II. Multiple Choice (1.5 points each). Write your name and fill in the circles using
a #2 pencil on the accompanying scantron card.
1) In the study of perceptual processes, the term “transduction” is defined to be
a) temporal patterning of nerve impulses.
b) neural processing.
c) the conversion of environmental energy into electrical energy.
d) electrical stimulation in the nervous system.
2) An experimenter inserts an electrode into the brain and records the electrical signals
from a neuron. Which of the following will he not observe while recording from this
neuron?
a) action potentials that all have the same duration
b) different firing rates for different types of stimuli
c) changes in the timing of action potentials with different types of stimuli
d) changes in the amplitude of action potentials with different types of stimuli
3) Which of the following is not an advantage of chemical synapse versus electrical
ones?
a) A chemical synapse can either excite or inhibit the postsynaptic neuron.
b) A chemical synapse is faster than a direct electrical connection.
c) The strength of a chemical synapse can be changed to enable learning.
d) A chemical synapse can be either fast or slow.
4) The method of fMRI measures neural activity ______ as changes in ______.
a) directly; electrical activity
b) indirectly; electrical activity
c) directly; blood flow & oxygenation
d) indirectly; blood flow & oxygenation
5) Which of the following methods has the best temporal resolution?
a) fMRI
b) PET
c) EEG
6) Two subjects’ thresholds on a visual detection task were measured using the
method of constant stimuli. A stimulus was presented on each trial and the subjects
reported whether they could see the target. Subject A detected 50% of the trials
while subject B detected only 40% of the trials at that intensity. Which of the
following interpretations can be made from this data?
a) Subject A is better at the task than subject B.
b) Subject A has a more liberal criterion than subject B.
c) Subject B has a more liberal criterion than subject A.
d) Subject B has more internal noise than subject A.
e) None of the above conclusions can be made.
7) If the just noticeable difference for lifting a 200-gram weight is 10 grams, the just
noticeable difference for lifting a 4,000-gram weight would be ______ grams.
a) 10
b) 40
c) 200
d) 400
8) In response to a pure tone, each point along the basilar membrane moves up and
down
a) with the same frequency but different amplitudes.
b) with the same frequency and the same amplitude.
c) with different frequencies and different amplitudes.
d) with different frequencies but the same amplitude.
9) If an audiogram shows hearing loss that is approximately equal across the range of
hearing, the problem is more likely to be due to
a) ugly wax build-up in the ear canal.
b) old age.
c) tinnitus.
d) macular degeneration.
10) Hair cells respond to auditory stimuli
a) with action potentials of constant amplitude.
b) with graded potentials (smooth changes in voltage).
11) The characteristic frequency of a neuron
a) indicates the rate at which the neuron usually fires.
b) is the only frequency to which the nerve fiber responds.
c) changes with the frequency of the stimulus.
d) is the frequency to which the neuron is most responsive.
12) A pure tone one octave above another tone has a frequency ______ of the lower
tone.
a) four times that
b) two times that
c) that varies with the amplitude
13) The tone complex depicted below will have the same perceived pitch as which of the
following pure tone frequencies?
a) 100 Hz
b) 200 Hz
c) 300 Hz
d) 400 Hz
14) Which of the following is true about critical bands?
a) The space that a critical band occupies on the basilar membrane is greater for
high center frequencies than low.
b) The frequency width of a critical band is constant regardless of the center
frequency.
c) When the bandwidth of a stimulus exceeds that of the critical band, the stimulus
sounds louder than a stimulus of equal energy but smaller bandwidth.
d) When the bandwidth of a stimulus is less than that of the critical band, the
stimulus sounds louder than a stimulus of equal energy but smaller bandwidth.
15) Damage to which of these areas is likely to specifically effect speech perception,
leaving patients with the ability to produce speech?
a) Broca’s Area
b) Wernicke’s area
c) A1
d) Cochlear nucleus
e) White’s area
16) An infant born with perfect vision wears an eye patch over one eye for much of her
first year of life. If given a vision test as an adult we will likely find that
a) her vision is worse in the patched eye than the other eye.
b) there is no vision problem because there has been more than enough time for a
complete recovery since she was an infant.
c) she is stereo blind.
d) a and c.
17) A patient complains of problems with her vision. A careful examination reveals that
when she closes her right eye, there is a large scotoma in the lower right quarter of
the left eye visual field. When she closes her left eye however, her vision is intact.
What could be the problem?
a) a puncture in the upper temporal part of retina of the left eye.
b) right optic nerve damage.
c) a lesion that has destroyed the left LGN.
d) a lesion that has damaged part of V1 in the right hemisphere.
18) The optic disc is located
a) on the nasal (close to the nose) part of the retina in both eyes.
b) on the temporal (close to the temples) part of the retina in both eyes.
c) on the nasal part of the retina in the right eye, but on the temporal part of the
retina in the left eye.
d) on the temporal part of the retina in the right eye, but on the nasal part of the
retina in the left eye.
19) What happens when a photoreceptor absorbs light energy?
a) the chemical structure of the photopigment molecule changes
b) the electrons in the photopigment molecule jump to higher energy states
c) the photopigment molecule’s spontaneous firing rate increases
d) the entire photoreceptor isomerizes
20) What is the Purkinje shift and why does it happen?
a) the shift in use of the rods to the use of the cones when light levels change from
low to high
b) the shift in your Purkinje tree, which is stabilized on the retina causing it to be
invisible even when your eyes shift
c) the shift from seeing color to being essentially color blind when light levels
change from photopic to scotopic conditions because we utilize different
photoreceptor systems
d) maximum spectral sensitivity shifts toward blue when light levels change from
photopic to scotopic conditions because we utilize different photoreceptor
systems
21) A spectrogram is a plot of
a) photoreceptor sensitivity vs. frequency.
b) sound intensity vs. frequency.
c) frequency vs. time.
d) the wavelength composition of the light source.
22) The color usually perceived at 470nm is ______; the color usually perceived at
700nm is ______.
a) red; blue
b) blue; red
c) green; blue
d) red; green
23) You have never seen a color that looks both green and red in your life. This can be
explained by:
a) trichromacy theory
b) color opponency theory
c) color constancy theory
d) dichromacy theory
24) Each layer of the LGN receives inputs from
a) both midget (parvo) and parasol (magno) ganglion cells.
b) either midget or parasol ganglion cells, but not both.
c) only one of the eyes.
d) a and c
e) b and c
25) What is an ocular dominance column?
a) A group of neurons in the retina of a person’s dominant eye.
b) A group of neurons in the visual cortex on the side of the brain opposite a
person’s dominant eye.
c) A group of neurons in the visual cortex that preferentially respond to either right
eye or left-eye stimulation.
d) A group of neurons in the visual cortex that preferentially respond to stimuli with
a particular orientation.
26) If we record from neurons along an electrode track that penetrates perpendicular to
the surface of the primary visual cortex, we find
a) neurons with largely overlapping receptive fields.
b) neurons with receptive fields that are systematically displaced from each other,
that is, with adjacent locations in the visual field.
27) While fixating object A, another object B falls on your horopter. You
a) will perceive B as being positioned closer than A.
b) will only be able to assess the distance to these objects if you change your
horopter.
c) will retain the same horopter if you shift your point of fixation from A to B.
d) can change the angle of disparity that each of the objects forms if your fixation
moves from A to B.
28) Most observers can see depth from binocular stereopsis without first extracting any
delineated or recognizable objects.
a) True.
b) False.
29) What range of depth is binocular disparity most useful for?
a) beyond the horopter only
b) the range in which binocular rivalry occurs
c) only for objects you are currently fixating
d) within arms length
30) Odysseus decides to trick his friend Polyphemus, a one-eyed giant, into thinking that
Odysseus is now his size. He beaches his ship on a long, featureless stretch of
sand, and positions himself a few hundred meters inland from the ship, holding out
his hand. When the giant comes down to the beach for his morning bath, he stops
and stares at Odysseus and the ship. The image of the ship at Polyphemus' retina is
five times smaller than the image of Odysseus and appears to be resting in
Odysseus' outstretched hand. Odysseus' prank succeeds because _____.
a) binocular vision is always necessary for depth perception.
b) monocular cues always provide sufficient information for an unambiguous
interpretation of size and depth.
c) Odysseus and the ship are perceived to be at the same distance.
d) the images of Odysseus and the ship project to different areas of the retina.
31) Motion aftereffects, such as the waterfall illusion, are most likely caused by
a) the autokinetic effect.
b) akinetopsia.
c) strabismus.
d) adaptation.
32) If you are moving straight ahead, the vectors (arrows) in your optical flow field
______ the object you are heading towards.
a) point away from
b) point perpendicular to
c) point toward
d) curve away from
33) A monkey is trained to perform a motion discrimination judgment on a field of dots
that have no coherent motion, i.e. the movement of the dots is random and
uncorrelated. On one trial, the experimenter records from a neuron in MT that is
selective for upward motion. On the next trial, the experimenter stimulates that same
upward-selective MT neuron. How would the monkey's behavior change from the
trial where the experimenter records from the MT neuron to the trial where the
experimenter stimulates the MT neuron?
a) The monkey would be more likely to respond that the dots are moving upward.
b) The monkey would be more likely to respond that the dots are moving
downward.
c) There would be no difference in the monkey's response during the two trials.
34) Which of the following is not a difference smooth pursuit and saccadic eye
movements?
a) saccades are ballistic and cannot be stopped once launched while smooth
pursuit eye movements are under constant control of the viewer
b) saccades are faster than smooth pursuit eye movements
c) saccades can be made in the dark while smooth pursuit eye movements require
a visual stimulus to follow
d) saccades are a biomechanical reflex programmed to keep fixation on a fixed
object in the world whereas smooth pursuit is a reflex programmed to keep
fixation on a moving object
35) Patient A has damage to the parietal lobes. Patient B has damage to the temporal
lobes. Which description is more likely to characterize the deficits shown by these
patients?
a) Patient A has difficulty recognizing objects and is unaware of his deficit. Patient
B has difficulty with spatial orientation and localization and is aware of his deficit.
b) Patient A has difficulty with spatial orientation and localization and is unaware of
his deficit. Patient B has difficulty recognizing objects, and is aware of his deficit.
c) Patient A has difficulty recognizing objects and is aware of his deficit. Patient B
has difficulty with spatial orientation and localization and is unaware aware of his
deficit.
d) Patient A has difficulty with spatial orientation and localization and is aware of his
deficit. Patient B has difficulty recognizing objects and is unaware of his deficit.
36) Blindsight
a) refers to the fact that damage to the cortex causes blindness.
b) occurs when a person who is blind claims that he or she can see.
c) occurs when a person can point to the location of a visual stimulus when forced
to guess, even though they have brain damage such that they are effectively
blind.
d) is a scientific hoax.
37) Although there have been many demonstrations that attention can affect the firing
rates of neurons in secondary cortical visual areas (like V4 and MT), cognitive
factors and task demands have no influence on activity in V1.
a) True
b) False
38) Subjects are given the following two visual search tasks. Which one will they be able
to do with shorter exposure to the stimulus?
a) Find a red X among green Xs, blue Os, yellow +s, and orange Ls.
b) Find a blue X among green Xs and blue Os.
39) In an experiment, subjects are asked to respond to a target stimulus as quickly as
possible by pressing a button. On some trials, the target stimulus is presented in the
right visual field and on the other trials the target stimulus is presented in the left
visual field. Before each stimulus is presented, the subjects are provided with a cue
specifying where the subject should focus their attention. Some of the cues are
valid, pointing to where the target will be presented. Some are invalid, pointing away
from where the target will be presented, and some are neutral, not specifying any
location. You would expect that reaction times would be fastest for the
_____________ trials, followed by the ______________, and then the
_______________ trials.
a) invalid, neutral, valid
b) valid, neutral, invalid
c) neutral, valid, invalid
d) valid, invalid, neutral
40) Which of the following is considered to be valid evidence against the hypothesis that
face recognition is functionally specialized?
a) After training, people are faster at recognizing upright relative to inverted
greebles (a novel class of object shapes).
b) Neurons in monkey inferior temporal cortex show selective responses to pictures
of monkey faces.
c) Studies have discovered a neuron in the temporal lobe of a human subjects’
brain that responds only to pictures of Bill Clinton.
d) Imaging studies have revealed regions of the human brain that respond more for
pictures of faces compared to houses and other non-face objects.
41) The infereotemporal (IT) cortex in the visual system has been suggested to be
functionally specialized for
a) color perception.
b) object perception.
c) motion perception.
d) depth perception.
42) Do any cells in the brain respond to illusory contours?
a) yes, in V1
b) yes, in V2
c) no, neurons only respond to physically real stimuli
Perception Final Exam Answer Sheet
Name:
Dec 18, 2006