Chapter 4 : Sensation and perception (3)

Question 1

Define ‘binocular cues’

Answer 1

Binocular depth cues are clues about distance based on the differing views of the two eyes.

Question 2

What is the principle binocular depth cue?

Answer 2

The principal binocular depth cue is retinal disparity, which refers to the fact that objects project images to slightly different locations on the right and left retinas, so the right and left eyes see slightly different views of the object.

The closer an object gets, the greater the disparity between the images seen by each eye.

Question 3

Name another binocular cue.

Answer 3

Another binocular cue is convergence, which involves sensing the eyes converging toward each other as they focus on closer objects.

Question 4

What are monocular depth cues?

Answer 4

Monocular depth cues are clues about distance based on the image in either eye alone

Question 5

What are the two types of monocular depth cues?

Answer 5

1. Motion parallax: involves images of objects at different distances moving across the retina at different rates.
2. Pictorial depth cues—clues about distance that can be given in a flat picture.

Question 6

What are the six prominent pictorial depth cues?

Answer 6

1. Linear perspective
2. Texture gradient
3. Interposition
4. Relative size
5. Height in plane
6. Light and shadow

Question 7

Define ‘perceptual constancy’.

Answer 7

A perceptual constancy is a tendency to experience a stable perception in the face of continually changing sensory input.

(for ex: snow appears white in the low illumination of moonlight, as well as in sunlight 800,000 times as bright.)

Question 8

What is a visual illusion?

Answer 8

A visual illusion involves an apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality

(CS)

Question 9

How are sound waves charcaterized?

Answer 9

Amplitude = loudness
Wavelength = pitch
Purity = timbre

Question 10

How are wavelengths of sound and amplitude measured in?

Answer 10

Wavelengths of sound are described in terms of their frequency, which is measured in cycles per second, or hertz (Hz).

Amplitude is measured in decibels (dB)

Question 11

How many sections can the ear be divided into?

Answer 11

The external ear, the middle ear, and the inner ear.

Question 12

Sound is conducted differently in each section. Explain.

Answer 12

The external ear depends on the vibration of air molecules.

The middle ear depends on the vibration of movable bones.

The inner ear depends on waves in a fluid,
which are finally converted into a stream of neural signals sent to the brain

Question 13

Explain how sound travels through the anatomy of the ear.

Answer 13

The external ear consists mainly of the pinna.

Sound waves collected by the pinna are funneled along the auditory canal toward the eardrum.

In the middle ear, the vibrations of the eardrum are transmitted inward by a chain made up of the three tiniest bones in your body (the hammer, anvil, and stirrup), known collectively as the ossicles

(CS)

Question 14

What are the functions of the pinna and eardrum?

Answer 14

Pinna: a sound-collecting cone
Eardrum: Sound waves collected by the pinna are funneled along the auditory canal toward the eardrum, a membrane that vibrates in response.

Question 15

What is the functions of the ossicles?

Answer 15

The ossicles form a three-stage lever system that converts relatively large movements with little force into smaller motions with greater force.

The ossicles serve to amplify tiny changes in air pressure

(CS)

Question 16

What does the inner ear consist of?

Answer 16

The inner ear consists largely of the cochlea, a fluid-filled, coiled tunnel that contains the receptors for hearing

Question 17

What are the two theories have dominated the debate on pitch perception?

Answer 17

Place theory and frequency theory

Question 18

What is Place theory and who postulated it?

Answer 18

Hermann von Helmholtz

He proposed that specific sound frequencies vibrate specific portions of the basilar membrane, producing distinct pitches, just as plucking specific strings on a harp produces sounds of varied pitch.

Question 19

Explain frequency theory and the person who proposed it.

Answer 19

(Rutherford, 1886). Frequency theory holds
that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates.

This theory views the basilar membrane
as more like a drumhead than a harp. According to frequency theory, the whole membrane vibrates in unison in response to sounds.

Question 20

What is auditory localization? What are the features/ cues that contribute to it?

Answer 20

Auditory localization—locating the source of a sound in space.

The intensity (loudness) and the timing of sounds arriving at each ear.

Question 21

Taste buds have a long life span. True or false?

Answer 21

False. Taste cells have a short life, spanning only about ten days, and they are constantly being replaced

Question 22

Explain the perception of taste.

Answer 22

Perceptions of taste quality appear to
depend on complex patterns of neural activity initiated by taste receptors.

Taste signals are routed through the thalamus and onto the insular cortex in the frontal lobe, where the initial cortical processing takes place.

(CS)

Question 23

Differentiate between supertasters, non-tasters and medium tasters.

Answer 23

People characterized as non-tasters, as determined by their insensitivity to iPROP (propylthiouracil), tend to have about one-quarter as many taste buds per square centimeter as people at the other end of the spectrum, who are called supertasters

The remaining 50 percent fall between these extremes and are characterized as medium tasters.

Question 24

Define ‘sensory adaptation’.

Answer 24

Sensory adaptation—a gradual decline in sensitivity to prolonged stimulation.

Question 25

What is the only sensory system that is not routed through the thalamus?

Answer 25

Smell is the only sensory system that is not routed through the thalamus before it projects onto the cortex.

Question 26

How are the olfactory system and the sensory smell system for smell similar?

Answer 26

1. The physical stimuli are chemical substances.
2. These chemical stimuli are dissolved in fluid—specifically, the mucus in the nose.
3. They resemble taste cells in that they
   have a short life and are constantly being replaced

(CS)

Question 27

Explain the pathway of tactile perception.

Answer 27

The nerve fibres that carry incoming information about tactile stimulation are routed through the spinal cord to the brainstem. There, the fibres from each side
of the body cross over, mostly to the opposite side of the brain.

(CS)

The tactile pathway then projects through the thalamus and onto the somatosensory cortex.

Question 28

Explain the two pathways pain messages are transmitted?

Answer 28

One is a fast pathway that registers localized pain and relays it to the cortex in a fraction of a second.

The second system uses a slow pathway that lags a second or two behind the fast system.

The slow pathway depends on thin, unmyelinated neurons called C fibres, whereas the fast pathway is mediated
by thicker, myelinated neurons called A-delta fibres

Question 29

Explain gate-control theory.

Answer 29

Gate-control theory holds that incoming pain sensations must pass through a “gate” in the spinal cord that can be closed, thus blocking ascending pain signals.