Perception Midterm 1
Prof. David J. Heeger
Oct 30, 2006
Read these instructions:
 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.
 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. List 2 reasons for why it is a good thing that most neurons communicate with
one another through chemical synapses instead of direct electrical contacts.
2. Describe an advantage of fMRI measurements over EEG. Describe an
advantage of EEG over fMRI.
3. You do an experiment in which you ask some friends to shake your head
back and forth to test the hypothesis that hearing depends on the motion of
your inner ear. You do not hear anything even though they are trying really
hard to shake you up. Explain why your experiment has failed, that is, explain
how sound depends on the motion of the inner ear, yet you don't hear a
sound when you move your head.
4. The middle ear is the space between the tympanic membrane and the
cochlea where the ossicular chain is located. This space is usually filled with
mostly with air but can sometimes become filled with fluid if you have a bad
cold or an ear infection. Why is it difficult to hear when your middle ear is filled
with fluid?
5. The following is a graph of a sound made by summing two pure tones: a 100
Hz tone plus a 200 Hz tone with half the amplitude. Draw the Fourier
spectrum graph corresponding to this sound and draw the spectrogram
corresponding to this sound. As always, label the axes.
Part II. Multiple Choice (2.5 points each). Write your name on the
accompanying scantron card (1 point) and fill in the circles using a #2 pencil.
1) Which of the following is not a characteristic of action potentials?
a) Action potential strength (peak voltage) is independent of stimulus
intensity.
b) Action potential rate (spikes per unit time) depends on stimulus intensity.
c) Action potentials self-propagate along the axon.
d) Once an action potential is triggered, it loses charge as it travels down the
axon and may eventually lose all charge, preventing any signal from
reaching the synapse.
e) Most cortical neurons use action potentials to transmit information.
2) Which part of neurons receives electrical signals from other neurons?
a) Cell body
b) Dendrites
c) Axon (or nerve fiber)
3) The process through which environmental energy is transformed into
electrical energy within the nervous system is called:
a) transmutation.
b) transduction.
c) transmission.
d) energy transfer.
4) An individual receiving electrical stimulation to the occipital lobe would most
likely report:
a) hearing something.
b) feeling something.
c) seeing something.
d) remembering something.
5) On the first 50 trials in a detection experiment a subject is given 10c for each
hit. On the second set of 50 trials she is told she will lose 10c for each false
alarm. We now expect that
a) her criterion will shift to the left.
b) her criterion will shift to the right.
c) her ROC curve will shift up-left.
d) her ROC curve will shift down-right.
6) Jim was participating in an psychophysics study in which he was asked to
discriminate which of two lights was brighter. Jim was having a very difficult
time with the experiment, so the researcher made the brighter light even
brighter. Which of the following statements best describes what happened to
d’ and why.
a) d’ increased because the brighter light had less noise
b) d’ increased because the separation between the two response probability
distributions (probability of occurrence curves) increased
c) d’ decreased as the separation between the two probability of occurrence
curves increased
d) d’ decreased because there was less overlap between the two probability
of occurrence curves due to a decrease in their spread.
7) In the Receiver Operating Characteristic (ROC) graph, what is the d prime
value for the performance along the diagonal?
a) 1
b) 0
c) –1
8) The difference threshold (also called “just noticeable difference” or JND) of a
100-gram weight is 5 grams, and the JND for discriminating the length of 100
cm stick is 5 cm. According to Weber’s law, we would expect that
a) the JND for discriminating any two weights is 5 grams.
b) the JND for discriminating the weight of a 1000-gram weight is 50 grams.
c) the JND for discriminating the length of any stick is 5 cm.
d) a and c.
9) Stevens’ power law predicts that:
a) doubling the intensity of a stimulus will cause less than a doubling of the
psychological perception of the stimulus.
b) doubling the stimulus intensity will cause more than a doubling of the
psychological perception of the stimulus.
c) Either of the above, depending upon the type of stimulus.
10) The two curves below show data from an experiment in which Laurie’s and
Chris’ thresholds for hearing a tone are determined by the method of constant
stimuli (or “Yes-No” method). According to signal detection theory
a) these data show that Laurie is more sensitive to the tone than Chris.
b) these data show that Chris is more sensitive to the tone than Laurie.
c) these data show that Laurie’s response criterion is lower than Chris’.
d) None of the above options are conclusively supported by the data.
11) The decibel scale is a scale for
a) timbre.
b) loudness.
c) pitch.
d) amplitude
e) frequency.
12) There are more outer than inner hair cells. Most of the nerves carrying
information from the auditory nerve onto higher brain areas receive their input
from the _________hair cells.
a) inner
b) outer
13) Permanent noise induced hearing loss occurs because of
a) damage to the middle ear muscles
b) damage to the auditory cortex
c) degeneration of hair cells
d) immobility of the bones in the middle ear
14) For a 100 Hz tone
a) the motion of the basilar membrane is greatest near the oval window.
b) the motion of the basilar membrane is greatest near the helicotrema.
c) near the oval window, the membrane oscillates up and down with a
frequency of 100 Hz.
d) b and c
15) While recording from the auditory nerve, we find a nerve fiber that has a
characteristic frequency of 1000 Hz. This nerve fiber will
a) never fire action potentials to any 100 Hz tone.
b) never fire action potentials to any 10,000 Hz tone.
c) fire more action potentials to a 1000 Hz tone than to a 100 Hz tone with
the same amplitude.
d) fire more action potentials to 1000 Hz than 100 Hz regardless of the
amplitudes.
16) You record from a single neuron in the auditory nerve, and find that it is phase
locked to a pure tone stimulus. This means that
a) it fires to every cycle of oscillation of the basilar membrane.
b) when it fires, it tends to fire near the peak of the cycle.
17) Musical tones usually consist of a single frequency
a) True
b) False
18) How do we test whether a system is linear?
a) test for homogeneity
b) test for additivity
c) test for shift invariance
d) all of the above
e) a and b only
19) If we hold a tone's ________ constant and increase its ___________, it will
sound louder.
a) amplitude; frequency
b) frequency; amplitude
c) timbre, frequency
20) The “volley principle”
a) was proposed by Jeffries to explain how timing differences could be used
for spatial localization.
b) was proposed by Bekesy to explain the motion of the basilar membrane.
c) was proposed by Wever to support the temporal code theory of pitch
perception.
d) was proposed by Helmholtz to support the place code theory of pitch.
21) Pitch is completely explained by:
a) Temporal Code Theory.
b) Place Code Theory.
c) Neither a nor b, because there are some pitch illusions that cannot be
readily explained by either theory.
22) John White used a cochlear implant to stimulate neurons in the inner ear and
asked the subject what pitch they perceived. Which statement is most
consistent his findings?
a) Temporal codes are only evident at very low (< 300 Hz) frequencies
b) Place coding is only evident at very low (<300Hz) frequencies
c) No evidence of temporal coding
d) No evidence of place codes
e) Both places codes and temporal codes are evident over the entire
frequency range of human hearing
23) In a matching experiment, a subject is most likely to match a complex tone
with components at 800, 1200, and 1600 Hz to a pure tone at what
frequency?
a) 200
b) 400
c) 800
d) 1200
e) 2000
24) A cochlear implant
a) amplifies the sound presented to the cochlea.
b) increases the amplitude of the vibration of the basilar membrane.
c) electrically simulates auditory nerve fibers.
d) amplifies the response of the hair cells.
25) A tonotopic map of frequency is represented in:
a) the cochlea.
b) the cochlear nucleus.
c) primary auditory cortex.
d) all of the above.
26) Interaural ______ differences in the sounds reaching the two ears are good
location cues only for ______ frequencies.
a) time; low
b) frequency; low
c) time; high
27) Below is a diagram of a person's head surrounded by 5 points in space. The
person is given the task of localizing sounds in space and the sound is
generated from each of these 5 points one at a time. For which of these pairs
of locations might the sounds appear to come from the same location?
a) 1 and 5
b) 2 and 3
c) 2 and 5
d) 3 and 4
1
3
2
4
5
28) Which of the following statements about phonemes is false?
a) Represent the smallest unit of speech that when changed alters the
meaning of a word.
b) A specific phoneme is always associated with exactly the same
spectrogram.
c) All vowel sounds are “voiced” whereas only some of the consonant
sounds are “voiced”.
d) Spectrograms for most consonant sounds are characterized by rapid
changes in frequency called formant transitions.
e) Spectrograms for vowel sounds are characterized by horizontal bands
called formants.
29) Damage to Broca’s area (an area of the frontal lobe near motor cortex) would
cause a person to have difficulty
a) distinguishing phonemes with short formant transitions.
b) producing speech.
c) understanding speech.
30) The Owl’s ability to determine interaural timing differences depends on
a) detecting the coincident arrival of action potentials from the two ears, one
of which has been delayed by having to propagate along a longer
segment of axon.
b) detecting the coincident arrival of action potentials from the two ears, one
of which has been delayed by an inhibitory neuron.
c) detecting the coincident arrival of action potentials from the two ears, one
of which has been delayed by propagating along a slower axon.
31) Which graph corresponds to how a neuron in the MSO responds to interaural
time differences?
a)
b)
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Perception Midterm 1
Oct 30, 2006
Answer Sheet
Name (1 point if legible):
Student number (0.5 points if legible):