CHapter 4 : Sensation and perception (2)

Question 1

What are the two types of receptors in the retina?

Answer 1

The retina contains two types of receptors, rods and cones.

Question 2

What are the functions of the cones?

Answer 2

1. Key role in daylight vision and colour vision.
2. Provide better visual acuity—that is, sharpness and precise detail—than rods.

Question 3

Where is visual acuity the greatest in the retina?

Answer 3

The fovea is a tiny spot in the centre of the retina that contains only cones; visual acuity is greatest at this spot.

Question 4

What are the functions of rods?

Answer 4

1. key role in night vision and peripheral vision.
   -Rods handle night vision because they are more sensitive than cones to dim light

They handle the lion’s share of peripheral vision because they greatly outnumber cones in the periphery of the retina.

Question 5

What is a receptive field?

Answer 5

The collection of rod and cone receptors that funnel signals to a particular visual cell in the retina (or ultimately in the brain) make up that cell’s receptive field.

Thus, the receptive field of a visual cell is the retinal area that, when stimulated, affects the firing of that cell.

( CS )

Question 6

What is the optic chiasm?

Answer 6

Axons leaving the back of each eye form the optic nerves, which travel to the optic chiasm—the point at which the optic nerves from the inside half of each eye
cross over and then project to the opposite half of the brain.

This arrangement ensures that signals
from both eyes go to both hemispheres of the brain

Question 7

Pathway of visual processing

Answer 7

( write on cheat sheet)

Question 8

What are the cells in the visual cortex characterized as?

Answer 8

Feature detectors, neurons that
respond selectively to very specific features of more complex stimuli.
(cs)

Question 9

What other processes is after the primary visual cortex

Answer 9

1. The ventral stream processes the details of what objects are out there (the perception of form and colour).
2. The dorsal stream processes where
   the objects are (the perception of motion and depth)

(CS)

Question 10

Explain the two types of colour mixtures.

Answer 10

Subtractive colour mixing works by removing some wavelengths of light, leaving less light than was originally there.

Additive colour mixing works by superimposing lights, putting more light in the mixture than exists in any one light by itself.

Question 11

What is the tri-chromatic theory and who proposed it?

Answer 11

The trichromatic theory of colour vision
holds that the human eye has three types of receptors with differing sensitivities to different light wavelengths.

By stated by Thomas Young and modified later by Hermann von Helmholtz.

Question 12

What was the impetus/catalyst of the tri-chromatic theory?

Answer 12

The impetus for the trichromatic theory was the demonstration that a light of any colour can be matched by the additive mixture of three primary colours.

(CS)

Question 13

If you stare at a strong colour and then look at a white background, what will you see?

Answer 13

You’ll see an afterimage—a visual image that persists after a stimulus is removed.

The colour of the afterimage will be the complement of the colour you originally stared at.

Question 14

What did tri-chromatic theory fail to do?

Answer 14

Trichromatic theory cannot account for the appearance of complementary afterimages.

Question 15

What is the opponent process theory and who proposed it?

Answer 15

Ewald Hering proposed the opponent process theory

The opponent process theory of colour vision holds that colour perception depends on receptors that make antagonistic responses to three pairs of colours.

The opponent process theory proposes that one member of the color pair suppresses the other color. For example, we do see yellowish-greens and reddish-yellows, but we never see reddish-green or yellowish-blue color hues.

Question 16

What is the accepted theory of colour?

Answer 16

George Wald demonstrated that the eye
has three types of cones, with each type being most sensitive to a different band of wavelengths.

Researchers also discovered a biological basis for opponent processes. They found cells in the retina, the LGN, and the visual cortex that respond in opposite ways to red versus green and blue versus yellow.

For ex, there are ganglion cells in the retina that are excited by green and inhibited by red. Other ganglion cells in the retina work in just the opposite way, as predicted in opponent process theory

Question 17

What is a perceptual set?

Answer 17

Perceptual set—a readiness to perceive a stimulus in a particular way. A perceptual set creates a certain slant in how someone interprets sensory input

( image that is a bunny or a duck, depending on where the subject is told to look at)

Question 18

Define change blindness.

Answer 18

Change blindness involves the failure to notice a seemingly obvious change in a visual display.

(observers failing to notice the gorilla enter into the room of people playing basketball)

Question 19

Define inattentional blindness.

Answer 19

Inattentional blindness is the failure to notice a fully visible, but unexpected object because attention was engaged on another task, event, or object.

(driving through a red light bec your attention was focused on texting)

Question 20

What is feature analysis?

Answer 20

Feature analysis is the process of detecting
specific elements in visual input and assembling them into a more complex form.

Feature analysis assumes that form perception involves bottom-up processing, a progression from individual elements to the whole

Question 21

What is the phi phenomenon?

Answer 21

The phi phenomenon is the illusion of movement created by presenting visual stimuli in rapid succession. (movies)

Question 22

What are the principles of Gestalt psychology?

Answer 22

1. Figure and ground: The figure is the thing being looked at, and the ground is the
   background against which it stands.
2. Proximity. Things that are close to one another seem to belong together
3. Closure. People often group elements to create a sense of closure, or completeness.
4. Similarity. People also tend to group stimuli that are similar.
5. Simplicity: Viewers tend to organize elements in the simplest way possible.
6. Continuity: Viewers tend to see elements in ways that produce a smooth continuation

Question 23

What are the two types of stimuli?

Answer 23

Distal stimuli are stimuli that lie in the distance (i.e., in the world outside the body.

Proximal stimuli, are the stimulus energies that impinge directly on sensory receptors.

(learn simple definition for midterm)

Question 24

What is ‘perceptual hypothesis’?

Answer 24

A perceptual hypothesis is an inference about which distal stimuli could be responsible for the proximal stimuli sensed.

(Educated guesses that we make while interpreting sensory information. These hypotheses are informed by a number of factors, including our personalities, experiences, and expectations)

For ex, I am sitting in my garden and register some fluttering in the periphery of my vision, then my internal brain states will change to encode the perceptual hypothesis that the sensations were caused by a bird. This minimizes my surprise about the fluttering sensations.

Question 25

What is depth perception?

Answer 25

Depth perception involves interpretation of visual cues that indicate how near or far away objects are.