Chapter 10 Definitions
The horopter is an imaginary circle passing through the point of fixation
A random dot stereogram consists of an image presented to one eye and an image presented to
the other eye. In a very simplified example, that second image is the same as the first image but
a portion of the image…is shifted spatially k
Select the term that is best described as perception that matches the actual physical situation
Which is not a Pictorial Monocular depth cue? Accommodation
Which is not a motion-produced depth cue ? Disparity
Absolute disparity The visual angle between the images of an object on the two retinas. When images of
an object fall on corresponding points, the angle of disparity is zero. When images fall
on noncorresponding points, the angle of disparity indicates the degree of
Accretion A cue that provides information about the relative depth of two surfaces. Occurs when
the farther object is uncovered by the nearer object due to sideways movement of an
observer relative to the objects. See also Deletion.
Ames room A distorted room, first built by Adelbert Ames, that creates an erroneous perception of
the sizes of people in the room. The room is constructed so that two people at the far
wall of the room appear to stand at the same distance from an observer. In actuality,
one of the people is much farther away than the other.
Angle of disparity The visual angle between the images of an object on the two retinas. When images of
an object fall on corresponding points, the angle of disparity is zero. When images fall
on noncorresponding points, the angle of disparity indicates the degree of
Angular size An explanation of the moon illusion that states that the perceived size of the moon is
contrast theory determined by the sizes of the objects that surround it. According to this idea, the
moon appears small when it is surrounded by large objects, such as the expanse of
the sky when the moon is overhead.
Apparent distance An explanation of the moon illusion that is based on the idea that the horizon moon,
theory which is viewed across the filled space of the terrain, should appear farther away than
the zenith moon, which is viewed through the empty space of the sky. This theory
states that because the horizon and zenith moons have the same visual angle, the
farther appearing horizon moon should appear larger.
A depth cue. Objects that are farther away look more blurred and bluer than objects
perspective that are closer because we must look through more air and particles to see them.
Binocular depth cell A neuron in the visual cortex that responds best to stimuli that fall on points separated
by a Glossary 409 specific degree of disparity on the two retinas. Also called a
Binocular disparity Occurs when the retinal images of an object fall on disparate points on the two retinas.
Conflicting cues A theory of visual illusions proposed by R. H. Day, which states that our perception of
theory line length depends on an integration of the actual line length and the overall figure
length. Correspondence The visual system’s matching of points on one image with similar points on the other
problem image in order to determine binocular disparity.
Corresponding The points on each retina that would overlap if one retina were slid on top of the other.
retinal points Receptors at corresponding points send their signals to the same location in the brain.
Cue approach to The approach to explaining depth perception that identifies information in the retinal
depth perception image, and also information provided by aiming and focusing the eyes on an object
that is correlated with depth in the scene. Some of the depth cues that have been
identified are overlap, relative height, relative size, atmospheric perspective,
convergence, and accommodation.
Deletion A cue that provides information about the relative depth of two surfaces. Deletion
occurs when a farther object is covered by a nearer object due to sideways movement
of an observer relative to the objects. See also Accretion.
Disparity-selective See Binocular depth cell.
Echolocation Locating objects by sending out high-frequency pulses and sensing the echo created
when these pulses are reflected from objects in the environment. Echolocation is used
by bats and dolphins.
Emmert’s law A law stating that the size of an afterimage depends on the distance of the surface
against which the afterimage is viewed. The farther away the surface, the larger the
Familiar size A depth cue. Our knowledge of an object’s actual size sometimes influences our
perception of an object’s distance.
Frontal efyes Eyes located in front of the head, so the views of the two eyes overlap.
Horopter An imaginary surface that passes through the point of fixation. Images caused by a
visual stimulus on this surface fall on corresponding points on the two retinas.
Lateral eyes Eyes located on opposite sides of an animal’s head, so the views of the two eyes do
not overlap or overlap only slightly, as in the pigeon and rabbit.
Müller-Lyer illusion An illusion in which two lines of equal length appear to be of different lengths because
of the addition of “fins’’ to the ends of the lines.
Misapplied size A principle, proposed by Richard Gregory, that when mechanisms that help maintain
constancy scaling size constancy in the three-dimensional world are applied to two-dimensional pictures,
an illusion of size sometimes results.
Monocular cue Depth cue, such as overlap, relative size, relative height, familiar size, linear
perspective, movement parallax, and accommodation, that works when we use only
Moon illusion An illusion in which the moon appears to be larger when it is on or near the horizon
than when it is high in the sky.
Motion parallax A depth cue. As an observer moves, nearby objects appear to move rapidly whereas
far objects appear to move slowly.
Noncorresponding Two points, one on each retina, that would not overlap if the retinas were slid onto
points each other. Also called disparate points.
Occlusion Depth cue in which one object hides or partially hides another object from view,
causing the hidden object to be perceived as being farther away.
Oculomotor cue Depth cue that depends on our ability to sense the position of our eyes and the tension
in our eye muscles. Accommodation and convergence are oculomotor cues.
Perspective The perception that parallel lines in the distance converge as distance increases.
Pictorial cue Depth cue, such as overlap, relative height, and relative size, that can be depicted in
pictures. Ponzo illusion An illusion of size in which two objects of equal size that are positioned between two
converging lines appear to be different in size. Also called the railroad track illusion.
Random-dot A pair of stereoscopic images made up of random dots. When one section of this
stereogram pattern is shifted slightly in one direction, the resulting disparity causes the shifted
section to appear above or below the rest of the pattern when the patterns are viewed
in a stereoscope.
Relative disparity The difference between two objects’ absolute disparities.
Relative height A depth cue. Objects that have bases below the horizon appear to be farther away
when they are higher in the field of view. Objects that have bases above the horizon
appear to be farther away when they are lower in the field of view.
Relative size A cue for depth perception. When two objects are of equal size, the one that is farther
away will take up less of the field of view.
Size constancy Occurs when the size of an object is perceived to remain the same even when it is
viewed from different distances.
Size–distance A hypothesized mechanism that helps maintain size constancy by taking an object’s
scaling perceived distance into account. According to this mechanism, an object’s perceived
size, S, is determined by multiplying the size of the retinal image, R, times the object’s
perceived distance, D.
Stereopsis The impression of depth that results from binocular disparity—the difference in the
position of images of the same object on the retinas of the two eyes.
Stereosdisparitcope A device that presents pictures to the left and the right eyes so that the binocular
disparity a person would experience when viewing an actual scene is duplicated. The
result is a convincing illusion of depth.
Texture gradient The visual pattern formed by a regularly textured surface that extends away from the
observer. This pattern provides information for distance because the elements in a
texture gradient appear smaller as distance from the observer increases.
Visual angle The angle of an object relative to an observer’s eyes. This angle can be determined by
extending two lines from the eye—one to one end of an object and the other to the
other end of the object. Because an object’s visual angle is always determined relative
to an observer, its visual angle changes as the distance between the object and the
Chapter 11: Sound, The Auditory System and Pitch Perception
o A pattern of air pressure changes caused by the virbration of an object
o We are only able to perceive the EFFECT of the object on the air, not directly
o What is X and Y axis ? Time vs Air pressure
o Diaphragm of speaker moves out
Air pushed together
o Back in
Decreased density of air
o Fourier frequency Spectrum? Y= intensity
o Our perceptual experience of a soundwave is related to the physical properties of the
1B Amplitude and Loudness
Related to amplitude
Physical aspect of external tone stimulus
o dB: Decibel -compressing the huge range of amplitude we can hear to a more
1C Frequency and Pitch
o Hz= Hertz 1 cycle per second
How high or low the tone sounds (perceptual experience)
Related to frequency
o Pitch: frequency :: loudness: amplitude
o Pitch is perceptual; frequency is physical
1D Complex Tones
o Fundamental frequency of a tone
There is a note associated with each piano key
Fundamental frequency increases from left to right
Each note contains energy at more than just this one frequency
o Fourier Analysis
Can break fown any complex tone into a set of simple sinewave components
that can be added up to create that complex tone
Ear does it
1E Range of Hearing
o We can hear 20-20,000 Hz
o Perceived loudness depends on amplitude (dB)
o Audibility Curve
How sensitivity changes across frequencies
o Threshold for Hearing
Plotted against tone freq
o Above threshold of FEELING sounds HURT
1F Sound Quality: Timbre
o When two tones with same loudness and pitch sound different
o More complex patterns of pressure changes than simple pure tones; cause different
Ii o Attack and Decay
How a sound starts and sustains
Play song they play backwards,
Now in right order but decay and attack are switched
We generally suppress perceptions of echoes for normal forward sounds
Backwards prevents this suppression
November 8, 2011
Chapter 11 Definitions
Fourier analysis is a mathematical technique that basically does what the ear does which enable
us to analyze a complex tone into its simple sine-wave components
For a tone with energy at frequencies of 300 Hz, 900, and 1200, if you remove 300 and play a
listener will say this sound has the same pitch as a tone with energy at 300 Hz only
What is associated with the point of maximum displacement along the Basilar Membrane?
Frequency of the pure tone BM is responding to
Humans can generally perceive sound in the range of 20-20,000 Hz
The Scala Tympani and Scala Vestibuli are separated by the cochlear partition
Pitch: Frequency :: loudness: amplitude
Pitch is perceptual; frequency is physical
Outer ear: frequency; middle ear: ossicles; inner ear:resonance
Additive In hearing, the process of building a complex tone by starting with the fundamental frequency and
synthesis adding pure tone harmonics.
Amplitude In the case of a repeating sound wave, such as the sine wave of a pure tone, amplitude represents
the pressure difference between atmospheric pressure and the maximum pressure of the wave.
Apex of the The end of the basilar membrane farthest from the middle ear.
Attack The buildup of sound at the beginning of a tone.
Audibility A curve that indicates the sound pressure level (SPL) at threshold for frequencies across the
curve audible spectrum
Auditory canal The canal through which air vibrations travel from the environment to the tympanic membrane.
receiving area The area of the cortex, located in the temporal lobe, that is the primary receiving area for hearing.
Auditory The psychophysically measured area that defines the frequencies and sound pressure levels over
response area which hearing functions. This area extends between the audibility curve and the curve for the
threshold of feeling. Base of the
cochlea The part of the basilar membrane nearest the middle ear.
Basilar A membrane that stretches the length of the cochlea and controls the vibration of the cochlear
Belt area Auditory area in the temporal lobe that receives signals from the core area and sends signals to the
frequency The frequency at which a neuron in the auditory system has its lowest threshold.
Cilia Fine hairs that protrude from the inner and outer hair cells of the auditory system. Bending the cilia
of the inner hair cells leads to transduction.
Cochlea The snail-shaped, liquid-filled structure that contains the structures of the inner ear, the most
important of which are the basilar membrane, the tectorial membrane, and the hair cells.
Cochlear How movement of the outer hair cells in response to sound increases basilar membrane vibration
amplifier and therefore amplifies the response of the inner hair cells.
Cochlear A device in which electrodes are inserted into the cochlea to create hearing by electrically
implant stimulating the auditory nerve fibers. This device is used to restore hearing in people who have lost
their hearing because of damaged hair cells.
nucleus The nucleus where nerve fibers from the cochlea first synapse.
Cochlear A partition in the cochlea, extending almost its full length, that separates the scala tympani and the
partition scala vestibuli. The organ of Corti, which contains the hair cells, is part of the cochlear partition.
Conductive Hearing loss that occurs when the vibrations of a sound stimulus are not conducted normally from
hearing loss the outer ear into the cochlea.
Core area The area in the temporal lobe that includes the primary auditory cortex (A1) and some nearby
areas. Signals from the core area are transmitted to the belt area of the auditory cortex.
Decay The decrease in the sound signal that occurs at the end of a tone.
Decibel A unit that indicates the presence of a tone relative to a reference pressure: dB 20 log (p/po) where
p is the pressure of the tone and po is the reference pressure.
Eardrum Another term for the tympanic membrane, the membrane located at the end of the auditory canal
that vibrates in response to sound.
Effect of the Removing the funda mental frequency and other lower harmonies from a musical tone does not
fundamental change the tone’s pitch. See also Periodicity pitch.
Envelope of A curve that indicates the maximum displacement at each point along the basilar membrane
wave caused by a traveling wave.
loudness A curve that indicates the sound pressure levels that result in a perception of the same loudness at
curve frequencies across the audible spectrum.
Frequency In the case of a sound wave that repeats itself, such as the sine wave of a pure tone, frequency is
the number of times per second that the wave repeats itself.
Frequency A plot that indicates the amplitudes of the various harmonics that make up a complex tone. Each
spectrum harmonic is indicated by a line that is positioned along the frequency axis, with the height of the line
indicating the amplitude of the harmonic.
tuning curve Curve relating frequency and the threshold intensity for activating an auditory neuron.
Fundamental The first harmonic of a complex tone; usually the lowest frequency in the frequency spectrum of a
frequency complex tone. The tone’s other components, called higher harmonics,have frequencies that are
multiples of the fundamental frequency. Hair cells Neuron in the cochlea that contains small hairs, or cilia, that are displaced by vibration of the basilar
membrane and fluids inside the inner ear. There are two kinds of hair cells: inner and outer.
Harmonics Fourier components of a complex tone with frequencies that are multiples of the fundamental
Hearing The experience of perceiving sound.
Hertz (Hz) The unit for designating the frequency of a tone. One Hertz equals one cycle per second.
Hierarchical Processing signals through a sequence of areas. This occurs in the visual system as signals are
processing transmitted from the LGN to the primary visual receiving area and then to higher areas. It occurs in
the auditory system as signals are transmitted from the core to the belt to the parabelt regions of
Incus The second of the three ossicles of the middle ear. It transmits vibrations from the malleus to the
Inferior A nucleus in the hearing system along the pathway from the cochlea to the auditory cortex. The
colliculus inferior colliculus receives inputs from the superior olivary nucleus.
Inner ear The innermost division of the ear, containing the cochlea and the receptors for hearing.
Inner hair cells See Hair cell, inner.
Leisure noise Noise associated with leisure activities such as listening to music, hunting, and woodworking.
Exposure to high levels of leisure noise for extended periods can cause hearing loss.
Level Short for sound level. Indicates the decibels or sound pressure of a sound stimulus.
Loudness The quality of sound that ranges from soft to loud. For a tone of a particular frequency, loudness
usually increases with increasing decibels.
Malleus The first of the ossicles of the middle ear. Receives vibrations from the tympanic membrane and
transmits these vibrations to the incus.
Medial An auditory nucleus in the thalamus that is part of the pathway from the cochlea to the auditory
geniculate cortex. The medial geniculate nucleus receives inputs from the inferior colliculus and transmits
nucleus signals to the auditory cortex.
The small air-filled space between the auditory canal and the cochlea that contains the ossicles.
Middle-ear Muscles attached to the ossicles in the middle ear. The smallest skeletal muscles in the body, they
muscles contract in response to very intense sounds and dampen the vibration of the ossicles.
Motile A response to sound of the outer hair cells in which these cells move. The cells tilt and get slightly
response longer, which increases basilar membrane vibration and therefore amplifies the response of the
inner hair cells.
Noise-induced A form of sensorineural hearing loss that occurs when loud noises cause degeneration of the hair
hearing loss cells.
Octave Tones that have frequencies that are binary multiples of each other (2, 4, etc.). For example, an
800-Hz tone is one octave above a 400-Hz tone.
Organ of Corti The major structure of the cochlear partition, containing the basilar membrane, the tectorial
membrane, and the receptors for hearing.
Ossicles Three small bones in the middle ear that transmit vibrations from the outer to the inner ear.
Outer ear The pinna and the external auditory meatus.
cells See Hair cells, outer.
Oval window A small, membrane-covered hole in the cochlea that receives vibrations from the stapes.
Parabelt area Auditory area in the temporal lobe that receives signals from the belt area.
Periodicity The constancy of a complex tone’s pitch when the fundamental frequency and other lower
pitch harmonics are eliminated. See also Effect o