Chapter 1 Introduction to Perception

Question 1

Describe allegory of a cave

Answer 1

The “Allegory of the Cave” is a scenario that says that our world is only made of what we are able to perceive. In this example, prisoners are in a dark cave. They are unable to move or see anything other than the shadows cast by objects and noises heard over a half wall made by a few guards in the cave. The shadows and noises comprise the entire world known by these prisoners, even if there are objects and noises beyond the cave exist.

As a result, we should not trust our senses because they cannot provide an accurate representation of our world

Question 2

Explain the mechanism of adaptation and provide an example.

Answer 2

Our brains quickly adapt to things that do not change for a period of time. For example, when one enters a house and they may initially be bombarded with the smell of fresh cookies, however, once some time has passed the smell of fresh cookies will not be noticed anywhere.

Question 3

What are sensory transducers and how are they related to perception?

Answer 3

Sensory transducers are receptors that convert physical energy from the environment into neural activity. According to Democritus, our perception is based on information passed through these receptors from the outside world.

Question 4

What is nativism?

Answer 4

Nativism is the belief that the mind creates thoughts outside of external experiences. That we possess innate abilities that exist before we experience anything.

Question 5

Explain why Descartes is known as a dualist.

Answer 5

Descartes is know as a dualist because he believes that our mind has an existence outside of the material world of the body.

Question 6

Describe empiricism and provide an example of one empiricist.

Answer 6

Empiricism is the philosophy that we are only made of our experiences and what we perceive. Ad that this is the only source of knowledge. John Locke is an example of an empiricist.

Question 7

Explain the notion of “tabula rasa.”

Answer 7

Tabula rasa is the belief that humans are born as a blank slate. We have no knowledge when we are brown. We must learn everything.

Question 8

What is psychophysics?

Answer 8

Psychophysics is defined as the science of defining quantitative relationships between physical and psychological (subjective) events.

Question 9

What is the “just noticeable difference” (JND)?

Answer 9

JND is the smallest detectable difference between two stimuli or the minimum change in a stimulus that enable it to be correctly judged as different from a reference stimulus.

Question 10

Describe two psychophysical methods used to measure people’s sensations.

Answer 10

1. ) Method of constant stimuli- a psychophysical method in which many stimuli, ranging from rarely to almost always perceivable (or rarely to almost always perceivably different from a reference stimulus) are presented one at a time. Participants respond to each presentation: “yes/no”’ “same/different” and so on.
2. ) Method of Limits- A psychophysical method in which the particular dimension of a stimulus, or the difference between two stimuli is varied incrementally until the participant responds differently.

Question 11

What is the method of adjustment?

Answer 11

–A method of limits in which the subject controls the change in the stimulus.

Question 12

Explain Fechner’s law.

Answer 12

Fechner’s law describes the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation increases proportionally to the logarithm of the stimulus intensity. S = k log R

Question 13

Why is the JND important in psychophysics?

Answer 13

JND is important in psychophysics because JND provides a reliable way to quantify data in reference to sensations and perceptions.

Question 14

What are the signal and noise in the signal detection theory?

Answer 14

The “signal” is the stimulus that one is trying to detect. The “noise” is the something that is always present, the background against which, we must detect the stimulus.

Question 15

What is magnitude estimation?

Answer 15

Magnitude estimation is defined as a psychophysical method in which the participant assigns values according to perceived magnitudes of the stimuli.

Question 16

What is the central idea of Müller’s doctrine of specific nerve energies?

Answer 16

States that the nature of a sensation depends on which sensory fibers are stimulated not on how fibers are stimulated.

Question 17

What are cranial nerves?

Answer 17

Twelve pairs of nerves (one for each side of the body) that originate in the brain stem and reach sense organs and muscles through openings in the skull.

Question 18

What is Helmholtz’s ophthalmoscope used for?

Answer 18

To view the retina

Question 19

Explain how neurons communicate with one another

Answer 19

Neurons communicate with each other by releasing neurotransmitters. These neurotransmitters move from the axon, across the synapse, and to receptors on the dendrite of the next neuron.

Question 20

What are neurotransmitters?

Answer 20

Neurotransmitters are a chemical substance used in neuronal communication a synapses.

Question 21

When is an action potential created?

Answer 21

Action potential is created when the membrane of the neuron permits sodium ions to rush into the cell, thus increasing the voltage. then potassium ions flows out of the cell, bringing the voltage back to a resting rate. This process occurs along the length of the axon until the action potential reaches the axon terminal.

Question 22

Overarching Principle of Perception

Answer 22

Perceptual systems evolve to obtain information about the environment that is relevant for the tasks the organism must perform in order to survive and reproduce.

Corollary: The design of a perceptual system is constrained by the tasks it performs, by the physical/statistical properties of the enviornment and various biological factors.

Question 23

Five difficult problems for Vision Systems

Answer 23

Illumination Problem-The Illumination of scenes is highly variable and complex

Depth Problem
Images in the eyes are 2D projections of a 3D environment

Context Problem
Objects often appear in a complex and varying context of other objects

Viewpoint Problem
Objects are rarely seen from the same viewpoint.

Category complexity problem
The specific objects that define a category are often quite different

Fundamental biological constraints
Limited neural resources, dynamic ranges and physical spaces.

Question 24

Recurrent Themes

Answer 24

Perception is a very complex process

Perception generally involves the integration of many sources of information most of which are not very reliable.

There are many approaches to the study of perceptual systems and each has made important contributions to our understanding.

Question 25

Approaches to Understanding Perception

Answer 25

``` Natural Tasks Natural Scene Statistics Anatomy Responses of individual neurons Responses of neural populations Perceptual/behavioral performance Mathematical and computational modeling ```

Question 26

Natural Tasks

Answer 26

Many of the major natural tasks involve natural sub-tasks. For example, image contours can occur for a number of entirely different physical reasons. They can be the result of surface boundaries, surface markings or shading. There can be little doubt that many perceptual tasks depend critically upon identifying whether a contour is a surface boundary, a marking or a shadow.

Question 27

Natural Scene Statistics

Answer 27

- Characterize natural stimuli - Identify sources of stimulus information available for performing natural tasks - Determine how useful are those sources of stimulus information - Generate hypothesis for how the brain might exploit the stimulus information - Design experiments to test the hypothesized mechanisms

Question 28

Two-Alternative Forced Choice Test

Answer 28

Example for an objective identification task with Feedback.

Question 29

abducens (VI) nerves

Answer 29

The sixth pair of cranial nerves, which innervate the lateral rectus muscle of each eye.

Question 30

absolute threshold

Answer 30

The minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time.

Question 31

auditory (VIII) nerves

Answer 31

The eighth pair of cranial nerves, which connect the inner ear with the brain, transmitting impulses concerned with hearing and spatial orientation. The auditory nerve is composed of the cochlear nerve branch and the vestibular nerve branch, leading to the alternate name vestibulocochlear nerve.

Question 32

blood oxygen level–dependent (BOLD) signal

Answer 32

The ratio of oxygenated to deoxygenated hemoglobin that permits the localization of brain neurons that are most involved in a task.

Question 33

computed tomography (CT)

Answer 33

An imaging technology that uses X-rays to create images of slices through volumes of material (e.g., the human body).

Question 34

cranial nerves

Answer 34

Twelve pairs of nerves (one for each side of the body) that originate in the brain stem and reach sense organs and muscles through openings in the skull

Question 35

criterion

Answer 35

In signal detection theory, an internal threshold that is set by the observer. If the internal response is above criterion, the observer gives one response (e.g., “yes, I hear that”). Below criterion, the observer gives another response (e.g., “no, I hear nothing”).

Question 36

cross-modality matching

Answer 36

The ability to match the intensities of sensations that come from different sensory modalities. This ability enables insight into sensory differences. For example, a listener might adjust the brightness of a light until it matches the loudness of a tone.

Question 37

cycles per degree

Answer 37

The number of pairs of dark and bright bars per degree of visual angle.

Question 38

doctrine of specific nerve energies

Answer 38

A doctrine, formulated by Johannes Müller, stating that the nature of a sensation depends on which sensory fibers are stimulated, not on how fibers are stimulated.

Question 39

dualism

Answer 39

The idea that the mind has an existence separate from the material world of the body.

Question 40

electroencephalography (EEG)

Answer 40

A technique that, using many electrodes on the scalp, measures electrical activity from populations of many neurons in the brain.

Question 41

event-related potential (ERP)

Answer 41

A measure of electrical activity from a subpopulation of neurons in response to particular stimuli that requires averaging many EEG recordings.

Question 42

Fechner’s law

Answer 42

A principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation increases proportionally to the logarithm of the stimulus intensity.

Question 43

Fourier analysis

Answer 43

A mathematical procedure by which any signal can be separated into component sine waves at different frequencies. Combining these sine waves will reproduce the original signal.

Question 44

functional magnetic resonance imaging (fMRI)

Answer 44

A variant of magnetic resonance imaging that makes it possible to measure localized patterns of activity in the brain. Activated neurons provoke increased blood flow, which can be quantified by measuring changes in of the response of oxygenated and deoxygenated blood to strong magnetic fields.

Question 45

just noticeable difference (JND) (or difference threshold)

Answer 45

The smallest detectable difference between two stimuli, or the minimum change in a stimulus that enables it to be correctly judged as different from a reference stimulus.

Question 46

magnetic resonance imaging (MRI)

Answer 46

An imaging technology that uses the responses of atoms to strong magnetic fields to form images of structures like the brain. The method can be adapted to measure activity in the brain, as well (see functional magnetic resonance imaging).

Question 47

magnetoencephalography (MEG)

Answer 47

A technique, similar to electroencephalography, that measures changes in magnetic activity across populations of many neurons in the brain.

Question 48

magnitude estimation

Answer 48

A psychophysical method in which the participant assigns values according to perceived magnitudes of the stimuli.

Question 49

materialism

Answer 49

The idea that the only thing that exists is matter, and that all things, including the mind and consciousness, are the results of interaction between bits of matter.

Question 50

method of adjustment

Answer 50

A method of limits in which the subject controls the change in the stimulus.

Question 51

method of constant stimuli

Answer 51

A psychophysical method in which many stimuli, ranging from rarely to almost always perceivable (or rarely to almost always perceivably different from a reference stimulus), are presented one at a time. Participants respond to each presentation: “yes/no,” “same/different,” and so on.

Question 52

neurotransmitter

Answer 52

A chemical substance used in neuronal communication at synapses.

Question 53

oculomotor (III) nerves

Answer 53

The third pair of cranial nerves, which innervate all the extrinsic muscles of the eye except the lateral rectus and the superior oblique muscles, and which innervate the elevator muscle of the upper eyelid, the ciliary muscle, and the sphincter muscle of the pupil.

Question 54

olfactory (I) nerves

Answer 54

The first pair of cranial nerves. The axons of the olfactory sensory neurons bundle together after passing through the cribriform plate to form the olfactory nerve, which conducts impulses from the olfactory epithelia in the nose to the olfactory bulb.

Question 55

optic (II) nerves

Answer 55

The second pair of cranial nerves, which arise from the retina and carry visual information to the thalamus and other parts of the brain.

Question 56

panpsychism

Answer 56

The idea that the mind exists as a property of all matter—that is, that all matter has consciousness.

Question 57

perception

Answer 57

The act of giving meaning to a detected sensation.

Question 58

period or wavelength

Answer 58

The time (or space) required for one cycle of a repeating waveform.

Question 59

phase

Answer 59

1) In vision, the relative position of a grating. (2) In hearing, the relative timing of a sine wave

Question 60

polysensory

Answer 60

Blending multiple sensory systems.

Question 61

positron emission tomography (PET)

Answer 61

An imaging technology that enables us to define locations in the brain where neurons are especially active by measuring the metabolism of brain cells using safe radioactive isotopes.

Question 62

psychophysics

Answer 62

The science of defining quantitative relationships between physical and psychological (subjective) events.

Question 63

quale (pl. qualia)

Answer 63

In philosophy, a private conscious experience of sensation or perception.

Question 64

receiver operating characteristic (ROC) curve

Answer 64

In studies of signal detection, the graphical plot of the hit rate as a function of the false-alarm rate. If these are the same, points fall on the diagonal, indicating that the observer cannot tell the difference between the presence and absence of the signal. As the observer’s sensitivity increases, the curve bows upward toward the upper left corner. That point represents a perfect ability to distinguish signal from noise (100% hits, 0% false alarms).

Question 65

sensation

Answer 65

The ability to detect a stimulus and, perhaps, to turn that detection into a private experience.

Question 66

sensitivity

Answer 66

In signal detection theory, a value that defines the ease with which an observer can tell the difference between the presence and absence of a stimulus or the difference between stimulus 1 and stimulus 2.

Question 67

signal detection theory

Answer 67

A psychophysical theory that quantifies the response of an observer to the presentation of a signal in the presence of noise. Measures obtained from a series of presentations are sensitivity (d′) and criterion of the observer.

Question 68

sine wave

Answer 68

(1) In hearing, a waveform for which variation as a function of time is a sine function. Also called pure tone. (2) In vision, a pattern for which variation in a property like brightness or color as a function of space is a sine function.

Question 69

spatial frequency

Answer 69

The number of cycles of a grating per unit of visual angle (usually specified in cycles per degree).

Question 70

Stevens’ power law

Answer 70

A principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent.

Question 71

supertaster

Answer 71

An individual whose perception of taste sensations is the most intense.

Question 72

synapse

Answer 72

The junction between neurons that permits information transfer.

Question 73

trochlear (IV) nerves

Answer 73

The fourth pair of cranial nerves, which innervate the superior oblique muscles of the eyeballs.

Question 74

two-point touch threshold

Answer 74

The minimum distance at which two stimuli (e.g., two simultaneous touches) are just perceptible as separate.

Question 75

vitalism

Answer 75

The idea that there is a force in life that is distinct from physical entities.

Question 76

Weber fraction

Answer 76

The constant of proportionality in Weber’s law.

Question 77

Weber’s law

Answer 77

The principle describing the relationship between stimulus and resulting sensation that says the just noticeable difference (JND) is a constant fraction of the comparison stimulus.

Question 78

abducens (VI) nerves

Answer 78

The sixth pair of cranial nerves, which innervate the lateral rectus muscle of each eye.

Question 79

absolute threshold

Answer 79

The minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time.

Question 80

auditory (VIII) nerves

Answer 80

The eighth pair of cranial nerves, which connect the inner ear with the brain, transmitting impulses concerned with hearing and spatial orientation. The auditory nerve is composed of the cochlear nerve branch and the vestibular nerve branch, leading to the alternate name vestibulocochlear nerve.

Question 81

blood oxygen level–dependent (BOLD) signal

Answer 81

The ratio of oxygenated to deoxygenated hemoglobin that permits the localization of brain neurons that are most involved in a task.

Question 82

computed tomography (CT)

Answer 82

An imaging technology that uses X-rays to create images of slices through volumes of material (e.g., the human body).

Question 83

cranial nerves

Answer 83

Twelve pairs of nerves (one for each side of the body) that originate in the brain stem and reach sense organs and muscles through openings in the skull

Question 84

criterion

Answer 84

In signal detection theory, an internal threshold that is set by the observer. If the internal response is above criterion, the observer gives one response (e.g., “yes, I hear that”). Below criterion, the observer gives another response (e.g., “no, I hear nothing”).

Question 85

cross-modality matching

Answer 85

The ability to match the intensities of sensations that come from different sensory modalities. This ability enables insight into sensory differences. For example, a listener might adjust the brightness of a light until it matches the loudness of a tone.

Question 86

cycles per degree

Answer 86

The number of pairs of dark and bright bars per degree of visual angle.

Question 87

doctrine of specific nerve energies

Answer 87

A doctrine, formulated by Johannes Müller, stating that the nature of a sensation depends on which sensory fibers are stimulated, not on how fibers are stimulated.

Question 88

dualism

Answer 88

The idea that the mind has an existence separate from the material world of the body.

Question 89

electroencephalography (EEG)

Answer 89

A technique that, using many electrodes on the scalp, measures electrical activity from populations of many neurons in the brain.

Question 90

event-related potential (ERP)

Answer 90

A measure of electrical activity from a subpopulation of neurons in response to particular stimuli that requires averaging many EEG recordings.

Question 91

Fechner’s law

Answer 91

A principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation increases proportionally to the logarithm of the stimulus intensity.

Question 92

Fourier analysis

Answer 92

A mathematical procedure by which any signal can be separated into component sine waves at different frequencies. Combining these sine waves will reproduce the original signal.

Question 93

functional magnetic resonance imaging (fMRI)

Answer 93

A variant of magnetic resonance imaging that makes it possible to measure localized patterns of activity in the brain. Activated neurons provoke increased blood flow, which can be quantified by measuring changes in of the response of oxygenated and deoxygenated blood to strong magnetic fields.

Question 94

just noticeable difference (JND) (or difference threshold)

Answer 94

The smallest detectable difference between two stimuli, or the minimum change in a stimulus that enables it to be correctly judged as different from a reference stimulus.

Question 95

magnetic resonance imaging (MRI)

Answer 95

An imaging technology that uses the responses of atoms to strong magnetic fields to form images of structures like the brain. The method can be adapted to measure activity in the brain, as well (see functional magnetic resonance imaging).

Question 96

magnetoencephalography (MEG)

Answer 96

A technique, similar to electroencephalography, that measures changes in magnetic activity across populations of many neurons in the brain.

Question 97

magnitude estimation

Answer 97

A psychophysical method in which the participant assigns values according to perceived magnitudes of the stimuli.

Question 98

materialism

Answer 98

The idea that the only thing that exists is matter, and that all things, including the mind and consciousness, are the results of interaction between bits of matter.

Question 99

method of adjustment

Answer 99

A method of limits in which the subject controls the change in the stimulus.

Question 100

method of constant stimuli

Answer 100

A psychophysical method in which many stimuli, ranging from rarely to almost always perceivable (or rarely to almost always perceivably different from a reference stimulus), are presented one at a time. Participants respond to each presentation: “yes/no,” “same/different,” and so on.

Question 101

neurotransmitter

Answer 101

A chemical substance used in neuronal communication at synapses.

Question 102

oculomotor (III) nerves

Answer 102

The third pair of cranial nerves, which innervate all the extrinsic muscles of the eye except the lateral rectus and the superior oblique muscles, and which innervate the elevator muscle of the upper eyelid, the ciliary muscle, and the sphincter muscle of the pupil.

Question 103

olfactory (I) nerves

Answer 103

The first pair of cranial nerves. The axons of the olfactory sensory neurons bundle together after passing through the cribriform plate to form the olfactory nerve, which conducts impulses from the olfactory epithelia in the nose to the olfactory bulb.

Question 104

optic (II) nerves

Answer 104

The second pair of cranial nerves, which arise from the retina and carry visual information to the thalamus and other parts of the brain.

Question 105

panpsychism

Answer 105

The idea that the mind exists as a property of all matter—that is, that all matter has consciousness.

Question 106

perception

Answer 106

The act of giving meaning to a detected sensation.

Question 107

period or wavelength

Answer 107

The time (or space) required for one cycle of a repeating waveform.

Question 108

phase

Answer 108

1) In vision, the relative position of a grating. (2) In hearing, the relative timing of a sine wave

Question 109

polysensory

Answer 109

Blending multiple sensory systems.

Question 110

positron emission tomography (PET)

Answer 110

An imaging technology that enables us to define locations in the brain where neurons are especially active by measuring the metabolism of brain cells using safe radioactive isotopes.

Question 111

psychophysics

Answer 111

The science of defining quantitative relationships between physical and psychological (subjective) events.

Question 112

quale (pl. qualia)

Answer 112

In philosophy, a private conscious experience of sensation or perception.

Question 113

receiver operating characteristic (ROC) curve

Answer 113

In studies of signal detection, the graphical plot of the hit rate as a function of the false-alarm rate. If these are the same, points fall on the diagonal, indicating that the observer cannot tell the difference between the presence and absence of the signal. As the observer’s sensitivity increases, the curve bows upward toward the upper left corner. That point represents a perfect ability to distinguish signal from noise (100% hits, 0% false alarms).

Question 114

sensation

Answer 114

The ability to detect a stimulus and, perhaps, to turn that detection into a private experience.

Question 115

sensitivity

Answer 115

In signal detection theory, a value that defines the ease with which an observer can tell the difference between the presence and absence of a stimulus or the difference between stimulus 1 and stimulus 2.

Question 116

signal detection theory

Answer 116

A psychophysical theory that quantifies the response of an observer to the presentation of a signal in the presence of noise. Measures obtained from a series of presentations are sensitivity (d′) and criterion of the observer.

Question 117

sine wave

Answer 117

(1) In hearing, a waveform for which variation as a function of time is a sine function. Also called pure tone. (2) In vision, a pattern for which variation in a property like brightness or color as a function of space is a sine function.

Question 118

spatial frequency

Answer 118

The number of cycles of a grating per unit of visual angle (usually specified in cycles per degree).

Question 119

Stevens’ power law

Answer 119

A principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent.

Question 120

supertaster

Answer 120

An individual whose perception of taste sensations is the most intense.

Question 121

synapse

Answer 121

The junction between neurons that permits information transfer.

Question 122

trochlear (IV) nerves

Answer 122

The fourth pair of cranial nerves, which innervate the superior oblique muscles of the eyeballs.

Question 123

two-point touch threshold

Answer 123

The minimum distance at which two stimuli (e.g., two simultaneous touches) are just perceptible as separate.

Question 124

vitalism

Answer 124

The idea that there is a force in life that is distinct from physical entities.

Question 125

Weber fraction

Answer 125

The constant of proportionality in Weber’s law.

Question 126

Weber’s law

Answer 126

The principle describing the relationship between stimulus and resulting sensation that says the just noticeable difference (JND) is a constant fraction of the comparison stimulus.