Chapter 4 : Sensation and perception (1)

Question 1

Differentiate between sensation and perception.

Answer 1

Sensation is the stimulation of sense organs.

Perception is the selection, organization, and interpretation of sensory input.

(Sensation involves the absorption of energy, such as light or sound waves, by sensory organs, such as the ears and eyes. Perception involves organizing and translating sensory input into something meaningful, such as your best friend’s face or other environmental stimuli)

Question 2

Explain how a person with synesthesia experiences perceptions and sensations.

Answer 2

Those who experience synesthesia,
a sensory experience in one domain is accompanied by a sensory experience in another domain.

(write the definition on cheat sheet + definition of emotional synesthesia )

Question 3

What is the field of psychophysics? Name an important contributor to it?

Answer 3

Psychophysics—the study of how physical stimuli are translated into psychological experience.

Gustav Fechner, in his formulations concerning sensory thresholds.

Question 4

Define ‘threshold’ and its two types.

Answer 4

A threshold is a dividing point between energy levels that do and do not have a detectable effect.

Two types of thresholds are key: absolute and difference thresholds.

( CS )

Question 5

What is the ‘absolute threshold’?

Answer 5

An absolute threshold for a specific type of sensory input is the minimum amount of stimulation that an organism can detect.

(detected 50 percent of the time)

Question 6

Define just noticeable difference.

Answer 6

A just noticeable difference (JND) is the smallest difference in the amount of stimulation that a specific sense can detect.

( CS )

Question 7

State Weber’s law

Answer 7

“difference thresholds are a constant proportion of the original stimulus.”

Weber’s law states that the size of a just noticeable difference is a constant proportion of the size of the initial stimulus.

(applies to all senses)

Question 8

State ‘signal-detection theory’.

Answer 8

Signal-detection theory proposes that the detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity.

Question 9

What are the possible outcomes in signal-detection theory?

Answer 9

1. Hits (detecting signals when they are present)
2. Misses (failing to detect signals when they are present)
3. False alarms (detecting signals when they are not present)
4. Correct rejections (not detecting signals when they are absent)

Question 10

Can sensory stimuli that fall beneath the threshold of awareness still influence behavior? / define subliminal perception.

Answer 10

This issue centres on the concept of subliminal perception—the registration of sensory input without conscious awareness

(limen is another term for threshold, so subliminal means “below threshold”)

Question 11

Define sensory adaptation.

Answer 11

Sensory adaptation is a gradual decline in sensitivity due to prolonged stimulation.

(ex:smokers are not bothered by the smell of smoke because they’re used it)

(also a factor that influences sensory input)

Question 12

What do light waves very in?

Answer 12

Light waves vary in amplitude
(height) and in wavelength (the distance between peaks).

Question 13

Name the physical properties of light and their related perceptions.

Answer 13

Amplitude = perception of brightness
Wavelength = perception of color
Purity = saturation or richness of colour

Question 14

What is purity of light?

Answer 14

The lights that humans normally
see are mixtures of several wavelengths.

Hence, light can also vary in its purity (how varied the mix is).

Question 15

What are the 2 purposes the eye serves?

Answer 15

(1)They channel light to the neural tissue that receives it, called the retina, and (2)they house that tissue.

Question 16

Which part of the eye creates the image of the visual world?

Answer 16

Light sensitive retina.

Question 17

How does an image form on the retina?

Answer 17

Light enters the eye through a transparent
“window” at the front, the cornea. The cornea and the crystalline lens, located behind it, form an upside-down image of objects on the retina.

Question 18

What is the lens of the eye and what process does it facilitate?

Answer 18

The lens is the transparent eye structure that focuses the light rays falling on the retina

Accommodation occurs when the curvature of the lens adjusts to alter visual focus. When you focus on a close object, the lens of your eye gets fatter (rounder) to give you a clear image.

Question 19

What is the iris and the pupil? What is the function of the pupil?

Answer 19

The iris is the coloured ring of muscle surrounding the pupil, or black centre
of the eye.

The pupil is the opening in the centre of the iris that helps regulate the amount of light passing into the rear chamber of the eye.

Question 20

What are the movements of the eye called?

Answer 20

The eye is constantly moving. These eye movements are referred to as saccades. These are important for good vision.

Question 21

What is saccade induced retrieval enhancement effect?

Answer 21

It has also been shown that saccadic eye movements can even enhance memory, for example, when horizontal eye movements are elicited before memory retrieval.

Question 22

What is the retina?

Answer 22

The retina is the neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain.

Question 23

What is the optic disk?

Answer 23

The axons that run from the retina to the brain converge at the optic disk, a place in the retina where the optic nerve fibres exit the eye.

Question 24

Why is the optic disk considered a blind spot?

Answer 24

There are no photoreceptors there, you cannot see the part of an image that falls on the optic disk. It is therefore known as the blind spot.