Week 9 & 10 - Sensation and Perception Flashcards
(172 cards)
1
Q
Sense
A
Is a system that translates information from outside the nervous system into neural activity
2
Q
Sensations
A
Are messages from the senses that make up the raw information that affects many kinds of behaviour and mental processes
3
Q
How do we sense?
A
With accessory structures and transduction
4
Q
All of these senses respond to:
A
Incoming stimulus energy, encode it in the form of nerve cell activity, and send this coded information to the brain
5
Q
Accessory structures
A
Are structures, such as the lens of the eye, that modify a stimulus. It reshapes the light or sound or other energy that comes to us from the environment.
6
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Transduction
A
Is the process of converting incoming energy into neural activity.
7
Q
Elements of the Sensory System:
A
Energy contains information about the world. 1. Accessory structure modifies energy. 2. Receptor transduces energy into neural activity. 3. Sensory nerves transfer the neural activity to the central nervous system. 4. Thalamus processes and relays the neural activity to the cerebral cortex. 5. Cerebral cortex receives input and produces the sensation and perception.
8
Q
Neural receptors
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Are specialised cells that detect certain forms of energy and transduce them into nerve cell activity
9
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Sensory adaptation
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Is the process through which responsiveness to an unchanging stimulus decreases over time
10
Q
Encoding
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Is the process of acquiring information and entering it into memory
11
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Specific Energy Doctrine
A
Is the discovery that stimulation of a particular sensory nerve provides codes for that sense, no matter how the stimulation takes pla
12
Q
How can psychologists measure perceptions when there is no way to get inside people’s heads to experience what they are experiencing?
A
One solution to this problem is to present people with lights, sounds and other stimuli and ask them to report their perception of the stimuli. This method of studying perception, called psychophysics, describes the relationship between physical energy in the environment and our psychological experience of that energy.
13
Q
How strong must a stimulus be in order to trigger a conscious perceptual experience?
A
Not very strong. Normal human vision can detect the light equivalent to a candle flame burning in the dark nearly 50 kilometres away.
14
Q
Absolute threshold
A
The smallest amount of light, sound, pressure or other physical energy that can be detected 50 per cent of the time. Example: the tick of a watch from 6 metres away.
15
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Subliminal stimulation
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Stimulation that is below the threshold that is too weak or too brief for us to notice.
16
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Supraliminal stimulation.
A
Stimulation that is above the absolute threshold and thus consistently perceived by humans. The stimulation that is strong.
17
Q
Signal detection theory
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Presents a mathematical model of how your personal sensitivity and response bias combine to determine your decision about whether or not a near-threshold stimulus occurred.
18
Q
Just-noticeable difference (JND)
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Is the smallest detectable difference in stimulus energy
19
Q
Weber’s law
A
Is a law stating that the smallest detectable difference in stimulus energy is a constant fraction of the intensity of the stimulus. This fraction, often called Weber’s constant or Weber’s fraction, is given the symbol K. K is different for each of the senses. The smaller K is, the more sensitive a sense is to stimulus differences.
20
Q
Magnitude estimation
A
Refers to how our perception of stimulus intensity is related to the actual strength of the stimulus (Fechner’s law).
21
Q
Types of human senses:
A
Vision Hearing Smell Touch Taste
22
Q
Sound
A
Is a repeated fluctuation, a rising and falling, in the pressure of air, water or some other substance called a medium.
23
Q
When you speak your vocal cords vibrate, producing fluctuations in air pressure that spread as waves. A wave is:
A
A repeated, rhythmic variation in pressure that spreads out in all directions.
24
Q
Physical characteristics of sound
A
Sound can be represented graphically by waveforms.
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Three characteristics of sound waveforms:
Amplitude (the difference between the peak and the baseline of a waveform). Wavelength (the distance from one peak to the next in a waveform). Frequency (the number of complete waveforms, or cycles, that pass a given point in space every second). Frequency is described in a unit called hertz (Hz). One cycle per second is 1 Hz.
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Are the wavelength and frequency related?
Yes. Because the speed of sound is constant in a given medium, wavelength and frequency are related: the longer the wavelength, the lower the frequency; the shorter the wavelength, the higher the frequency. Most sounds are mixtures of many different frequencies and amplitudes.
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The physical characteristics of sound waves (amplitude and frequency) determine the
Psychological dimensions of sound which are: Loudness. Pitch and; Timbre.
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Loudness
is determined by the amplitude of the sound wave; waves with greater amplitude create sensations of louder sounds. Loudness is described in units called decibels, abbreviated to dB. By definition, 0 dB is the minimum detectable sound for normal hearing.
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Pitch
How high or low a tone sounds. Humans can hear sounds ranging from about 20 Hz to about 20 000 Hz.
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Almost everyone hears relative pitch; that is, people can tell whether one note is higher than, lower than or equal to another note. However, some people have absolute pitch, more commonly known as perfect pitch, which means that:
They can identify specific frequencies and the notes they represent. They can say, for example, that a 262-Hz tone is middle C. Though perfect pitch appears to be an inborn trait, it may also be possible to develop it through learning.
31
Timbre
Is the mixture of frequencies and amplitudes that make up the quality of sound. It is determined by complex wave patterns that are added onto the lowest, or fundamental, frequency of a sound.The extra waves allow you to tell, for example, the difference between a note played on a flute and the same note played on a clarinet.
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The human ear converts sound energy into:
Nerve cell activity through a series of accessory structures and transduction mechanisms.
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The amplitude, frequency and complexity of sound waves determine the:
Loudness, pitch and timbre of sound.
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Accessory structures
Pinna, tympanic membrane, malleus, incus, stapes, oval window, basilar membrane
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Sound waves are collected in:
The outer ear, beginning with the pinna. The pinna funnels sound down through the ear canal. At the end of the ear canal, the sound waves reach the middle ear, where they strike a tightly stretched membrane known as the eardrum, or tympanic membrane. The sound waves cause matching vibrations in the tympanic membrane. The vibrations of the tympanic membrane then pass through a chain of three tiny bones: the malleus, or hammer; the incus, or anvil; and the stapes, or stirrup. These bones amplify the vibrations coming from the tympanic membrane by focusing them onto a smaller membrane called the oval window. When sound vibrations pass through the oval window, they enter the inner ear, reaching the cochlea.
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Cochlea
A fluid-filled spiral structure of the ear in which transduction occurs.
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Basilar membrane
The floor of the fluid-filled duct that runs through the cochlea. Whenever a sound wave passes through the fluid in the tube, it causes the basilar membrane to move up and down, and this movement bends hair cells of the organ of Corti, a group of cells resting on the membrane. These hair cells connect with fibres from the acoustic nerve, also known as the auditory nerve. When the hair cells bend, they stimulate neurons in the acoustic nerve to fire, and the pattern of firing creates a coded message that tells the brain about the amplitude and frequency of the incoming sound waves. We experience this information as loudness and pitch.
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The acoustic nerve, also known as the auditory nerve is:
A bundle of axons that goes into the brain.
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The middle and inner ear are among the most delicate structures in the body. If they deteriorate or are damaged \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
Deafness can result.
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Types of deafness
Conduction deafness: occurs when the bones of the middle ear fuse together, thus preventing accurate conduction of vibrations from one bone to the next. Nerve deafness, results when the acoustic nerve or, more commonly, the hair cells are damaged. This occurs gradually with age, but it can also be caused more quickly by extended exposure to the noise of jet engines, industrial equipment, gunfire, loud music and other intense sounds.
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Before sounds can be heard, the information encoded in the firing of the many axons that make up the acoustic nerve must be sent to the brain for further analysis.This transmission process begins when the acoustic nerve conveys the information to the:
Thalamus. From there, the information is relayed to the primary auditory cortex, an area in the temporal lobe of the brain.
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Auditory cortex
Is the area in the brain’s temporal lobe that is the first to receive information about sounds from the thalamus. It is in the primary auditory cortex that information about sound is subjected to the most intense and complex analysis. This auditory analysis may be especially efficient in people who were deprived of visual experience because of blindness in early life.
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Preferred frequencies
Is when different cells fire more vigorously in response to sounds of particular frequencies.
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The frequency of a _________ determines the ______ that you experience
Sound; Pitch
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Frequency is coded in two ways, which are described by the:
Place theory and frequency-matching theory.
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Place theory
Is a theory that hair cells at a particular place on the basilar membrane respond most to a particular frequency of sound called a characteristic frequency. In other words, place theory describes a spatial, or place-related, code for frequency. When hair cells at a particular location respond to a sound, we hear a pitch that is at the characteristic frequency of those cells. One important result of this arrangement is that extended exposure to a very loud sound of a particular frequency can destroy hair cells at one spot on the basilar membrane, making it impossible to hear sounds of that frequency.
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Frequency-matching theory.
Explains the coding of very low frequencies, such as that of a deep bass note. That is because humans can hear frequencies as low as 20 Hz. The lowest sound frequencies are coded by frequency matching, whereby the frequency is matched by the firing rate of auditory nerve fibres. Low-to-moderate frequencies are coded by both frequency matching and the place on the basilar membrane at which the wave peaks. High frequencies are coded only by the place at which the wave peaks.
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Volley theory
The view that some sounds are coded by matching the frequency of neural firing
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Light is a form of energy known as:
Electromagnetic radiation. Most electromagnetic radiation (including X-rays, radio waves, television signals and radar) is invisible to the human eye. In fact, the range, or spectrum, of visible light is just the tiny slice of electromagnetic radiation whose wavelength is from just under 400 nanometres (nm) to about 750 nanometres (a nanometre is one-billionth of a metre).
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Visible light
Is electromagnetic radiation that has a wavelength of approximately 400–750 nanometres
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Sensations of light depend on two physical dimensions of light waves:
Intensity and wavelength.
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Light intensity
Refers to how much energy the light contains; it determines the brightness of light, much as the amplitude of sound waves determines the loudness of sound.
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Light wavelength
Is the distance between peaks in light waves. What colour you sense depends mainly on light wavelength. At a given intensity, different wavelengths produce sensations of different colours, much as different sound frequencies produce sensations of different pitch
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Visual transduction
Occurs when light energy is transduced into nerve cell activity in the eye.
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Process of focusing light
Before the transduction process occurs, accessory structures in the human eye modify incoming light rays. The light rays enter the eye by passing through a transparent, protective layer called the cornea. Then the light passes through the pupil, the opening just behind the cornea. The iris, which gives the eye its colour, adjusts the amount of light allowed into the eye by constricting to reduce the size of the pupil or relaxing to enlarge it. Directly behind the pupil is the lens. The cornea and the lens of the human eye are both curved so that, like the lens of a camera, they bend light rays. The light rays are focused into an image on the surface (retina) at the back of the eye. Light rays from the top of an object are focused at the bottom of the image on the retinal surface. Light rays from the right side of the object end up on the left side of the retinal image .The brain rearranges this upside-down and reversed image so that we can see the object as it is.
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Cornea
The curved, transparent, protective layer through which light rays enter the eye.
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Pupil
An opening in the eye, just behind the cornea, through which light passes.
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Iris
The colourful part of the eye, which constricts or relaxes to adjust the amount of light entering the eye.
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Lens
The part of the eye behind the pupil that bends light rays.
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Retina
The surface at the back of the eye onto which the lens focuses light rays
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Ocular accommodation
The ability of the lens to change its shape and bend light rays so that objects are in focus
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In some older people, vision is impaired by
Cataracts, a condition in which a ‘cloudy’ lens severely reduces incoming light. Cataracts can be cleared up with laser surgery or by replacing the natural lens with an artificial one
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You see objects as they are because your brain:
Rearranges the upside-down and reversed images that the lens focuses on the retina.
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A common eye condition in younger people is:
Nearsightedness, in which close objects are in focus but distant ones are blurry. This condition is partly genetic but it may also be made more likely by environmental factors, such as when people spend more time looking at close-up images and less time far-gazing.
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Photoreceptors
Are specialised cells in the retina that convert light energy into nerve cell activity. The photopigments: are chemicals in photoreceptors that respond to light and assist in converting light into nerve cell activity.
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The eye has three major layers
The sclera: which s the white part of our eye which maintains, protects, and supports the shape of the eye and includes the cornea; The choroid, which provides oxygen and nourishment to the eye and includes the pupil, iris, and lens; and The retina, which allows us to piece images together and includes specialised cells such light receptors known as cones and rods.
67
Dark Adaptation
Is the increasing ability to see in the dark as time passes. In the dark, as your photoreceptors create more photopigments, your ability to see gradually increases. In fact, you become about 10 000 times more sensitive to light after about half an hour in a darkened room.
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The retina has two main types of photoreceptors:
Rods and cones which differ in shape, but they also differ in their response to light.
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Rods
Rods have only one pigment, so they respond about equally to all wavelengths. As a result, rods can’t help us discriminate colours, but they are more sensitive to light than cones are. They do not detect colour. They allow vision even in dim light. The photopigment in rods includes a substance called rhodopsin.
70
Cones
Are photoreceptors in the retina that help us distinguish colours. Cones in the fovea. The photopigment in cones includes one of three kinds of iodopsin. There are three types of cones, each most sensitive to particular wavelengths. Short- wavelength cones respond most to light in the blue range. Medium-wavelength cones are most sensitive to light in the green range. Long-wavelength cones respond best to light in the reddish-yellow range (these have traditionally been called ‘red cones’). No single type of cone can signal the colour of a light; it is the ratio of responses by the three types of cones that determines the colour you see. We see colour because our three types of cones have different sensitivities to different wavelengths..We sense different colours when the three cone types are stimulated in different ratios.
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Fovea
Is a region in the centre of the retina where cones are highly concentrated. Here is where the eye focuses the light coming from objects you look at.
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Visual acuity (or ability to see details)
Is visual clarity, which is greatest in the fovea because of its large concentration of cones.
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Optic nerve
Is a bundle of fibres composed of axons of ganglion cells that carries visual information to the brain
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\_\_\_\_\_\_\_\_\_\_\_\_ and ___________ allow the eye to begin analysing visual information even before that information leaves the retina.
Bipolar cells and ganglion cells.
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Ganglion cells
Can act as photoreceptors and detect a bit of light all by themselves, but this information seems to be used mainly for keeping our internal body clocks synchronised with the light and dark cycles of the world around us.
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When it comes to using light for conscious visual sensations, we rely on the photoreceptor work of
Rods and cones, and the information that they send into bipolar cells and ganglion cells.
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So no matter where you look, all the visual information about the right half of the visual world goes to the\_\_\_\_\_\_\_\_\_\_\_\_\_\_ of your brain and all the visual information from the left half of the visual world goes to the _______________ of the brain.
Left hemisphere; right hemisphere
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Feature detectors
Are cells in the cortex that respond to a specific feature of an object
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At a given intensity, each ____________ of light is seen as a certain \_\_\_\_\_\_\_.
Wavelength; colour
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The 3 characteristics of wavelength mixture that determine our sensation of colour.
Hue, saturation and brightness.
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Hue
Is the essential ‘colour’, determined by the dominant wavelength in the mixture of the light that enters the eye. For example, the wavelength of yellow is about 570 nanometres and that of red is about 700 nanometres. Black, white and grey are not considered hues because no wavelength predominates in them.
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Colour Saturation
Is related to how pure a colour is. A colour is more saturated (more pure) if just one wavelength is relatively more intense (contains more energy) than other wavelengths. If many wavelengths are added to a pure hue, the colour is said to be desaturated. For example, pastels are colours that have been desaturated by adding whiteness
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Brightness
Is the overall intensity of all of the wavelengths that make up light.
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How the unit of wavelengths of light is measured?
With nanometres (Nm),
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Trichromatic theory
Is a theory of colour vision identifying three types of visual elements, each of which is most sensitive to different wavelengths of light. All colours in the spectrum can be produced by combining red, green, and blue. There are three receptor types in the eye each sensitive to specific colour: red, green and blue light.
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Opponent-process theory
Colour-sensitive visual elements in the eye are arranged into three kinds of pairs, and that the members of each pair oppose, or inhibit, each other. Each element signals one colour or the other (red or green, blue or yellow, black or white), but never both. This theory explains colour afterimages.When one member of an opponent pair is no longer stimulated, the other is activated.
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So what do Trichromatic and Opponent-ProcessTheories Combined explain?
Zone Theories. Each theory describes physiological mechanisms in the visual system.
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What does Trichromatic theory explain? What do opponent-process theory explain?
Trichromatic theory explains the responses of the cones in the retina. It explains colour vision as it relates to rods and cones, Opponent-process theory explains neural response for cells connected to the cones further in the brain. It explains colour vision as it relates to the ganglion cells. Both theories are needed to account for the complexity of colour sensations.
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Colour blindness
Is a condition in which the lack of certain photopigments leaves a person unable to sense certain colours
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Colour vision depends on what happens in the:
Brain – especially in the cortex – where encoded colour information from the retinas is assembled and processed.
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Monochromats
Have a very rare genetic condition which results in a lack of functional cones receptors. Hence they are truly colour blind and must rely on their rods for vision. As cones are concentered in the fovea and necessary for visual acuity, monochromats not only experience the world without colour (shades of grey,) but they also lack visual acuity. Their reliance on rod vision also means that they are very sensitive to bright light.
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Dichromatisms
Colour deficiencies such as dichromatisms are a result of genetic mutations which alter the body’s ability to produce one or more of the three required groups of photopigments within cones. There are three types of dichromatism. Protanopia is one type of dichromatism resulting in a severe form of red-green colour blindness, in which there is impairment in perception of very long wavelengths, such as reds.
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How do we make sense of a 3D world when we see in 2D?
With depth perception which is an approach that focuses on information in the retinal image. We learn the connection between cue and depth, and association becomes automatic through repeated exposure. A range oculomotor, monocular and binocular cues are available from the 2D visual scene that our brain uses to create a perception of a third dimension. Oculomotor cues are based on sensing the position of the eyes and muscle tension. Ocular convergence cues are created by the inward movement of our eyes when we focus on nearby objects. The fact that depth perception is possible with only one eye shows there are visual depth cues in our environment which do not rely on binocular vision, such as monocular depth cues. Monocular cues refer to cues that come from one eye. Pictorial cues refer to sources of depth information that come from 2D images, such as pictures.
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How can colours be changed?
Intensity-Saturation (adding white to colour results in less saturated colour)- Wave length.
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Colours of objects are determined by the wavelengths that are
Reflected; Reflectance curves: plots of percentage of light reflected for specific wavelengths. Chromatic colours or hues: objects that preferentially reflect some wavelengths called selective reflectance. Achromatic colours - contain no hues (White, black, and gray tone).
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Pictorial Cues:
Relative size: when objects are equal size, the closer one will take up more of your visual field. Perspective convergence/linear perspective: parallel lines appear to come together in the distance. Familiar size: distance information based on our knowledge of object size. Atmospheric perspective: distance objects are fuzzy and have a blue tint (on a clear day). Texture gradient: equally spaced elements are more closely packed as distance increases. Shadows: indicate where objects are located. Enhance 3-D of objects.
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Trichromatic colour theory is most applicable at the level of \_\_\_\_\_\_\_\_\_\_\_, while opponent-process colour theory is most applicable at the level of \_\_\_\_\_\_\_\_\_\_\_.
Photoreceptors; ganglion cells
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While walking outside, you notice the sun shining. Your ability to see the sunshine is related to visual processing of the light in your brain. The process by which physical energy (the sunshine) has been converted to neural activity in your brain is called:
Transduction
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Are messages from the senses that provide a map of the world outside of the brain.
Sensations
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When Aaron plays touch rugby with his friends, he gets tagged several times while running the ball. Depending on where he is tagged, say on the arm or on the leg, neurons in different locations fire for that particular sensation. This is an example of ___________ encoding.
Spatial
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The distance from one peak to the next in a waveform.
The wavelenght of a sound.
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The observation that constant increases in physical energy produce progressively smaller increases in perceived magnitude forms the basis of which psychophysics law?
Fechner’s law
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Your task is to look at a computer screen and press a button every time you see a flash of light appear. If the point of light is presented at the absolute threshold, you would press the button ___________ of the time that the light is flashed.
50%
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\_\_\_\_\_\_\_\_\_\_\_ suggests that hair cells at a particular place on the basilar membrane respond most to a particular frequency of sound.
Place Theory
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As you and your friend walk across the street toward the cafeteria, she says, ‘Oh, I can smell the lobster from here.’ You, however, can’t smell it yet. Which of the following explanations is the most plausible?
She has a lower absolute threshold than you.
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What is perception?
The process through which people take raw sensations from the environment and interpret them, using knowledge, experience and understanding of the world, so that the sensations become meaningful experiences A largely UNCONSCIOUS, AUTOMATIC process, based on 'unavailable' neural events, together with 'unconscious' inferences from specific cues.
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Does perception require conscious effort?
SOMETIMES, when interpreting sensory data (e.g when data are ambiguous and incomplete).
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What is "effortlessness of perception"?
The disguise of the complex nervous systems mechanisms operating (behind the scenes).
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What are the two interacting aspects of perception?
Bottom-up processing: processing based on incoming stimuli from the environment (AKA data-based processing). Bottom-up processing is accomplished by the analysis of stimulus features or combinations of features, such as form, colour and motion. Top-down processing: processing based on the perceiver's previous Knowledge (cognitive factors), expectations and other psychological factors. AKA knowledge-based processing. Top-down processing is influenced by expectancy and motivation.
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Perceptual failures
Cases in which our perceptual experience of a stimulus differs from the actual characteristics of that stimulus.
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Three approaches to perception
Computation model Constructivist approach Ecological approach
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Computation model
Tries to determine the calculations that a computer would have to perform to solve perceptual problems. Psychologists taking this computational approach believe that understanding these calculations will help them explain how complex computations within the nervous.
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Constructivist approach
Argue that our perceptual systems construct a representation of reality from fragments of sensory information. Constructivists emphasise that our perception is strongly influenced by what we have learned from our experiences and by the expectations and inferences that those experiences create. These psychologists are particularly interested in situations in which the same stimulus creates different perceptions in different people. For example, a desk might prevent you from seeing the lower half of a person seated behind it, but you still ‘see’ the person as a complete human being. Experience tells you to expect that people remain intact even when parts of them are obscured.
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Ecological approach
Claims that most of our perceptual experience comes directly from the wealth of information contained in the stimuli coming to us from the environment rather than from our interpretations, inferences and expectations.
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\_\_\_\_\_\_\_\_\_\_\_ focuses on the nervous system’s manipulations of incoming signals, _____________ emphasises the inferences that people make about the environment, and the\_\_\_\_\_\_\_\_\_\_ emphasises the information provided by the environment.
The computational approach; the constructivist approach ; ecological approach.
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Perceptual organisation
Is the task performed by the perceptual system to determine what edges and other stimuli go together to form an object.
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Basic processes in perceptual organisation
Figure ground discrimination: the ability to organise a visual scene so that it contains meaningful figures set against a less relevant ground. Certain objects or sounds are automatically identified as figures, whereas others become meaningless background. Example: you see a person standing against a building, not a building with a person- shaped hole in it. Grouping: properties of stimuli lead us to automatically group them together. These include proximity, similarity, continuity, closure, texture, simplicity, common fate, synchrony, common region and connectedness. (Gestalt Laws). Example: people who are sitting together or who are dressed similarly are perceived as a group
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Gestalt psychologists proposed a number of principles, or ‘Gestalt laws’, that describe how perceptual systems group stimuli into a world of shapes and objects and these are:
SEE PAGE 143 AND 144 of the chapter. Its images. These include proximity, similarity, continuity, closure, texture, simplicity, common fate, synchrony, common region and connectedness.
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One of the most important perceptual tasks we face is to determine where objects and sound sources are located. This task involves knowing both their two-dimensional position (left or right, up or down) and their distance from us. How this works?
The image on the retina and the orientation of the head provide information about the two-dimensional position of visual stimuli; auditory localisation relies on differences in the information received by the ears. Depth or distance perception uses stimulus cues such as interposition, relative size, height in the visual field, gradient of texture, linear perspective, clarity, colour and shadow. Example: a person who looks tiny and appears high in the visual field is perceived as being of normal size but at a great distance.
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The ability to perceive distance is called:
Depth perception
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Interposition or occlusion:
A depth cue whereby closer objects block one’s view of things farther away.
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Linear perspective
A depth cue whereby objects closer to the point at which two lines appear to converge are perceived as being at a greater distance
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Gradient of texture
Graduated change in the texture, or grain, of the visual field, whereby objects with finer, less detailed textures are perceived as more distant. Example: the details of a scene or photo fade gradually as distance increase.
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Motion parallax
Is a depth cue whereby a difference in the apparent rate of movement of different objects provides information about the relative distance of those objects. Example: you may have noticed that when you look out the side window of a moving car, objects nearer to you seem to speed across your visual field, whereas objects in the distance seem to move slowly, if at all.
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Eye convergence
The relative location of our two eyes produces two other depth cues. The first is called eye convergence. Because the eyes are located a short distance apart, they must converge, or rotate inward, to project an object’s image on each retina. The brain receives information about this movement from the eye muscles and uses it to help calculate an object’s distance.The closer the object, the more the eyes must converge, which sends more intense stimulation to the brain.
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Retinal disparity or binocular disparity.
Because of the eye differing locations, each eye receives a slightly different view of the world. Is the difference between the two retinal images of an object.
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Perception of motion
Many of the cues of motion come from optical flow, or the changes in retinal images across the entire visual field. Looming: is a motion cue caused by a rapid expansion in the size of an image so that it fills the retina. Stroboscopic illusion: an illusion of motion that is created when we see slightly different images or slightly displaced lights flashed in rapid succession. Stroboscopic motion is based on the organising principles of likelihood and simplicity. Objects in the world do not usually disappear, only to be immediately replaced by a similar object nearby. Accordingly, your brain makes the simpler and more likely assumption that a disappearing and reappearing object has move.
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When objects appear, disappear and then quickly reappear nearby, you perceive them as moving smoothly from the first location to the next. The same illusion occurs when flashing lights on a cinema or casino sign seem to move around the sign. This is an example of?
Stroboscopic illusion.
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Perceptual constancy
Is the perception of objects as constant in size, shape, colour and other properties despite changes in their retinal image. Example: a train coming towards you is perceived as getting closer, not larger; a restaurant sign is perceived as rotating, not changing shape.
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People who have lost an eye also lose the depth cue called:
Retinal disparity
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\_\_\_\_\_\_\_\_\_\_ people use their knowledge in making inferences or ‘educated guesses’ to recognise objects, words or melodies, especially when sensory information is vague or ambiguous. Example: police officers find it easy to identify familiar people on blurry security camera videos, but it is much more difficult for them to identify strangers.
In top-down processing,
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Top-down processing can have a strong influence on pattern recognition. Our experiences create:
Schemas, which are mental representations of what we know and have come to expect about the world. Schemas can bias our perception towards one recognition or another by creating a perceptual set, a readiness or predisposition to perceive a stimulus in a certain way.
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Word superiority effect
Is when strings of letters are briefly flashed on a screen, people’s ability to detect target letters is better if the string forms a word than if it is a non-word
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In one study, participants were asked to say whether a particular feature, like a dot or angled line, appeared within a pattern that was briefly flashed on a computer screen. The participants detected this feature faster when it was embedded in a pattern resembling a three-dimensional object than when it appeared within a random pattern of lines.This result is called the
Object superiority effect.
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Parallel distributed processing (PDP)
Is a theoretical model of object recognition in which various elements of the object are thought to be simultaneously analysed by several widely distributed but connected neural units in the brain.
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Mental representations (generalisations) of categories of objects, events and people.
Schemas
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Multimodal Processing & Attention
Johannes Peter Muller proposed the law of specific nerve energies. According to Muller, regardless of the type of stimulation, a particular sensory nerve can only provide the codes for its corresponding sense. For example, regardless of how we stimulate the optic nerve, it can only encode information about our visual environment. However, this notion is somewhat challenged in the cases of cross-modal processing.
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McGurk effect
Shows us that sound perception can be influenced by information from other senses, particularly vision. Having experienced the McGurk effect your perception was essentially shifted by the conflicting visual and auditory information. This illustrates that although auditory information is the major source of information for speech perception, visual information can also exert a strong influence on what we hear – audio-visual speech perception. The McGurk effect is one example of audio-visual (multimodal) perception, but another is the way we use a speakers lip movements to help understand speech in a noisy environment.
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Synaesthesia
Is a blending of sensory experience that causes people to experience cross-modal sensations. Example: some people ‘see’ sounds or ‘taste’ colours or like hearing sounds when they see colours, or tasting colours.
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Attention is a central process and __________ is not possible without attentional processes. That means:
Perception; attention precedes perception.
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Attentional processes serve various functions in the organization of our perceptions and other cognitive functions. The various functions of attention are :
1. Alerting function: Attention in this sense refers to a state of focused awareness with readiness to respond (e.g., if asked some question). Distraction occurs when some interference (e.g., loud noise) prevents the individual to continue with the ongoing task. 2. Selective attention: Selective attention acts as a filter, that allows some information in and the other (unwanted) information out. 3. Divided attention: If you have ever multi-tasked, you would know that it is possible to complete two tasks at once (i.e., divided attention), but this can only occur only under specific conditions. If one or both of those tasks are highly practised or routinized then it is possible to carry on with two tasks simultaneously. 4. Vigilance or Sustained Attention: Maintaining attention on a task continuously, for some time, like looking at the radar screen, is called vigilance or sustained attention. It has been found that attending to a task for a long time is taxing, particularly if the task is monotonous and it leads to a decrease in performance. You will be able to understand vigilance better by doing the following activity.
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Have you ever noticed that when you are in a crowded room, you can focus on one conversation seemingly tuning out the noise around you? You might say that you were listening to what your friend was saying but that you were unable to register anything going on in the room. This is called: the "tea-party effect" (generally referred to as cocktail–party effect). And this is an example of:
Selective attention
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For example, when you are a practised driver, you can drive the car as well as converse with the other person sitting by your side. However, attentional resources are of a limited capacity, which means that if a task requires increased attentional resources (when the task is difficult) you can only carry on with one task at a time. This is called:
Serial processing; The bottle-neck is at the central level (in the brain). That is, the brain is not able to handle two or more tasks simultaneously.
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Perception is the result of a blending of __________ and \_\_\_\_\_\_\_\_\_.
Heredity and environment. From infancy onwards, the perceptual system creates a personal reality based in part on the experience that shapes each individual’s feature analysis networks and knowledge-based expectancies.
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There are several different types of perceptual constancies we rely on
Including shape, size and colour constancy.
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Shape constancy
We perceive the shape to be the same no matter what angle we are looking at it from. For instance, a door that is closed is still perceived a rectangular object as it swings open and shuts close, despite the changes the appearance of its shape on the retina while in motion . Rather we see it a rectangular shape-changing position rather than overall shape while in motion. Our idea of shape constancy ensures that objects retain their shape no matter how we see them.
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Size Constancy
Is our tendency to perceive an object as being the same size regardless of whether it is close or far away. For instance, we don’t perceive the height of someone to be increasing as they walk towards us from a distance
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Colour Constancy
this refers to our tendency perceived colour of objects as remaining stable despite constant variation in illumination conditions. The overall colour of objects is stable in the morning light compared to evening light and indoors compared to outdoors
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The Gestalt Approach
This approach provided rules and regulations for top-down processing and this influenced the bottom-up ideas of structuralism. The central point is that the whole is greater than the sum of its parts. The sensations that form the perception, aren’t just what we perceive, the whole then, the final perception is greater because of top-down perception with experience and memory influencing what we perceive.
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Attention
Is the process of directing and focusing psychological resources to enhance perception, performance and mental experience.
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Psychologists have discovered three important characteristics of attention:
It improves mental processing. You often have to concentrate attention on a task to do your best at it. If your attentional system temporarily malfunctions, you might drive right past Barney’s Cafe. Attention takes effort. Prolonged concentration of attention can leave you feeling drained and when you are already tired, focusing attention on attention the process of directing and focusing attention on anything becomes more difficult. Attentional resources are limited. If your attention is focused on reading this book, for example, you’ll have less attention left over to listen to a conversation in the next room.
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Our ability to search for targets rapidly and automatically is called:
Parallel processing. It is as if you can examine all nearby locations at once (in parallel) and rapidly detect the target no matter where it appears. So if the sign you are looking for is bright red and twice as large as any other one on the road, you could conduct a parallel search, and the sign would quickly stand out. The automatic parallel processing that allows detection of colour or size suggests that these features are analysed before the point at which attention is required.
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True or false: Colour recognition is so automatic, it is thought that colour is analysed before the point at which attention is required.
True
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The process of directing and focusing psychological resources to enhance perception, performance and mental experience is called\_\_\_\_\_\_\_\_.
Attention
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A task that requires little or no attention is said to be \_\_\_\_\_\_\_\_.
Automatic
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Attention is a linked set of resources that improves \_\_\_\_\_\_\_\_\_\_\_.
Information Proccesing
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True or False: Evidence of the extra mental work attention requires is found using positron emission tomography (PET) and magnetic resonance imaging (MRI) scan.
True
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You can direct your perceptual systems towards different aspects of your external and internal environments by:
Overt orienting
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Pointing sensory systems at a particular stimulus or by shifting attention without having to move a muscle is called:
Covert orienting
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Inattentional blindness
Is a failure to detect or identify normally noticeable stimuli.
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True or False: Control over attention can be voluntary and knowledge-based or involuntary and driven by environmental stimuli.
True.
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True or False: Some information can be processed automatically, in parallel, whereas other situations demand focused attention and a serial search.
True
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True or False: Although the brain plays a critical role in attention, no single brain region has been identified as the main attention centre.
True
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The grouping principle of _________ allows you to identify objects seen through a picket fence.
Closure
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\_\_\_\_\_\_\_\_\_\_\_ is a motion cue caused by a rapid expansion in the size of an image so that it fills the retina.
Looming
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When Monet paints haystacks, he depicts the haystacks that are closer to him with a lot of detail but the ones further away with less detail. Monet is using the depth cue of:
Gradient of texture
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The task of determining what edges and other stimuli go together to form an object is known as:
Perceptual organization
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You are driving and staring at two trees far off in the distance. You can estimate the distance between the trees by the way they appear to move relative to one another, using the cue of:
Motion parallax
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Fabio had been driving for over 12 hours. He was hungry and tired, so he began looking for a place to spend the night. He read a sign that he thought said ‘Red Roof Inn’, but when he pulled into the parking lot, he realised that the sign read ‘Reed Roofing, Inc.’ Fabio’s perception that the sign was for the national hotel chain and not a roofing company was most likely due to ___________ processing.
Top Down
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According to research on perception in infants, the first thing that infants should be able to do after birth is to:
Pay attention to human face.
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Upon awakening from a nap, you open your eyes and immediately have the image of a cat’s paw rapidly expanding on your retina. Which concept explains why you perceive this image as moving and not as an expanding object fixed in space?
Perceptual constancy
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Rebecca’s new boyfriend Andy takes her to a 3D movie. In an effort to impress Rebecca, Andy explains to her that the movie appears to be three-dimensional by providing each eye with slightly different images, thus creating the illusion of depth. Andy can’t remember what this phenomenon is called, but Rebecca, tired of Andy’s showing off, tells him it is called:
Retinal Disparity.
