Sensation and perception

Question 1

Sensation vs Perception

Answer 1

Sensation: Translates environmental stimulus into nerve
impulses that are sent to the brain via
transduction. Passive.

Perception: making “sense” of sensation. Organizing the raw stimulus /sensory data and giving it meaning. Active

Question 2

5 steps from distal stimulus to percept

Answer 2

1. Distal stimulus
2. Transduction of stimulus into electrochemical energy
3. Proximal stimulus- The initial sensation.
4. Process of inference (Schlussfolgerung)
5. Percept: Mental representation that we experience.

Question 3

Distal vs Proximal stimulus

Answer 3

Distal: What is seen
Proximal: What is projected onto the retina. (Switched)

Question 4

Describe 7 aspects of the human eye

Answer 4

1. Light enters through the cornea.
2. The pupil is an adjustable opening behind the cornea,
   managing the amount of incoming light.
3. The iris is colored and contains muscles that control the
   size of the pupil.
4. The lens reverses the image entering the eye, and
   projects it onto the retina.
5. The retina contains rods and cones (photoreceptor cells)
6. Blind spot (optic disk): Where the optic nerve exits the
   eye to the brain. Has no receptors.
7. Fovea. In the center of the retina. Has no rods, but many
   densely packed cones.

Question 5

Rods vs Cones

Answer 5

Rods: Operate at low light intensities. Do not detect colour, but detect small amounts of light. On the retina’s periphery.
Cones: Operate at high light intensities. Detect colour and fine details. Located in the centre of the retina.

Question 6

Where does visual information have to pass to reach the primary visual cortex?

Answer 6

It has to pass the Lateral Geniculate Nucleus (LGN)

Question 7

Ecological view of perception (Gibson)

Answer 7

Perception is direct, and not subject to hypotheses testing. There is enough information in our environment to make sense of the world in a direct way. His theory is sometimes known as the ‘Ecological Theory’ because of the claim that perception can be explained solely in terms of the environment.

Question 8

The “stimulus” in ecological perception

Answer 8

• The distal stimulus
• The environment of that stimulus
• What our body tells us about the stimulus
  - Is it near or far?
  - Is it flexible or rigid?
  - Is it moving or stable?

Question 9

How do we perceive depth?

Answer 9

Through the convergence of our eyes and retinal disparity.

Question 10

What is retinal disparity?

Answer 10

Each eye receives a somewhat different image, because they are separated by a few centimetres. The two 2D images from the eyes are merged into one 3D image in the brain: Stereoscopic vision!

Question 11

What’s accommodation?

Answer 11

Lens bulges to focus on nearby objects, and flattens to focus on faraway objects.

Question 12

Name two monocular cues for the perception of distance

Answer 12

1. Superposition (things in front cutting off things in back)
2. Linear perspective (vanishing point)

Question 13

What are perceptual constancies?

Answer 13

Stimulus information is changing, but perception remains the same. Perception is based on knowledge. It is not equal to stimulus.

Question 14

What are reversible images/figures?

Answer 14

Perception changes despite stability in stimulus. The visual information fits with multiple templates in our brain. No template can be sorted out. Perception is not equal to stimulus.

Question 15

How does Helmholz differentiate between Perception and sensation?

Answer 15

Sensation: Unconscious interferences (going beyond apparent information)

Perception: Shaped through knowledge, expectations and beliefs. Can also act on cultural differences.

Question 16

What is selective attention?

Answer 16

Focusing on one specific thing and ignoring the rest of the scene. OR focusing on/expecting one event to happen due to a cue that happens prior to the event.

Question 17

What’s the cocktail party effect?

Answer 17

Being able to focus on one specific stimulus, even though there is much going on around you/following one conversation at a loud cocktail party.

Question 18

Switching attention

Answer 18

Being able to switch focus during the cocktail party effect, through a specific cue (eg your name)

Question 19

Give an example for change blindness

Answer 19

Eg.: People giving directions not noticing when the person they are giving directions to changes

Question 20

How does a stimulus turn into perception in the brain?

Answer 20

Distal stimulus falls on sensory receptors

Distal stimulus is turned into proximal stimulus

Transduction- Proximal stimulus is transformed into a pattern of neural impulses

These are transmitted to the brain

The Brain makes sense of them: perceptual processes.

Question 21

Which areas of the brain are affected by the following:

• Cortical blindness
• Visual neglect
• Prosopagnosia

Answer 21

• Occipital lobe
• Parietal lobe
• Temporal lobe

Question 22

What is blindsight?

Answer 22

Loss of vision. Patients are still able to recognize objects around them (mostly unconsciously), often walk around them.

Question 23

What is cortical blindness?

Answer 23

A form of blindsight. Evolved through a lesion (damage) in the occipital cortex. There are three kinds:

• Half field lesion: Half of the visual field is affected
• Local lesion: A point on the visual field is affected
• Quarter field lesion: About a quarter of the visual field is affected.

Question 24

What is spatial neglect?

Answer 24

Damage to right parietal lobe. Patient ‘extinguishes’ objects in their left visual field. They do not know that they are doing this. There is no left for them/they won’t move their head (if they would do so they would probably notice).

Question 25

What is agnosia?

Answer 25

Damage to the temporal lobe. Loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant
memory loss.

Question 26

What is prosopagnosia?

Answer 26

Damage to the fusiform gyrus in the temporal lobe, where faces are processed. It sends signals to the amygdala, which assesses the emotion of what you are looking at/assigns emotion to the face. Prosopagnosia is the loss of ability to recognize faces.