Lecture 4

Question 1

Gestalt psychologists - 6 perceptions

Answer 1

1. simplicity
2. closure
3. continuity
4. similarity
5. proximity
6. common fate

Question 2

Simplicity

Answer 2

We perceive the simplest shape possible.

Question 3

Closure

Answer 3

We fill in missing elements.

Question 4

Continuity

Answer 4

Edges or contours of shapes that have similar orientation provide ‘good continuation’.

Question 5

Similarity

Answer 5

Similar looking areas of a visual display are perceived as belonging to the same object.

Question 6

Proximity

Answer 6

Objects close together tend to be grouped together.

Question 7

Common fate

Answer 7

Elements that move together are part of the same moving object.

Question 8

Image based theories + problem

Answer 8

An object you have seen before is stored in memory as a template which can be compared to the retinal representation.

• Problem: variability in position, size, shape, and orientation.

Question 9

Other race effect (own race bias)

Answer 9

People are better at recognising/discriminating faces from their own race compared to other races (evident among all people from all different races).

Question 10

The basic subcomponents of features + problem

Answer 10

Theory: About 36 geons are needed to recognise all visual objects.

• Problem: the theory does not provide a mechanism that reduces complex real scenes to geon representations and geons fail to distinguish many real objects.

Question 11

Current view of perception

Answer 11

Checking expectations (priors) with sensory evidence.

Question 12

Fusiform face area (FFA)

Answer 12

The FFA responds strongly to faces, whereas other pictures like houses, objects, scenes, bodies are scrambled pictures.

Question 13

The Thatcher effect

Answer 13

Upright races are processed differently than upside-down ones.

Question 14

Important topics for perception (6)

Answer 14

1. Object size
2. Monocular depth cues
3. Familiar size
4. Binocular depth cues
5. Binocular disparity
6. Motion

Question 15

Object size (equation)

Answer 15

Retinal Representation x Distance

Question 16

Monocular depth cues

Answer 16

• Relative Height: Things at a distance look like their base is higher.
• Relative Size: Objects farther away from other objects are smaller.

Question 17

Familiar size

Answer 17

Judging size based on what you already know (e.g., adult male height).

Question 18

Binocular depth cues

Answer 18

A large part of central visual field is registered in both eyes.
The size of the retinal representation in the left and right eye is slightly different (because of the different positions of the two eyes).

• Binocular cues are depth cues that require the use of two eyes. For instance, trying to touch the tip of two pencils together in front of your face may be rather easy to do with both eyes open; however, attempting this task with one eye open is significantly challenging.

Question 19

Binocular disparity - size

Answer 19

Left and right eye see the world in a different perspective. The brain creates a 3D image of this difference (stereopsis).
The bigger the difference, the closer the object.

• Hollow mask illusion

Question 20

Motion

Answer 20

• Object close to observers seem to move faster than objects further.
• Before motion can be inferred, the visual system has to know whether the movement on the retina is caused by a displacement of the (1) eye, head, body or (2) movement of the object.

Question 21

Apparent motion

Answer 21

Successive alternating signals induce a motion perception (if not, a movie would look like a slide show).

• In the ‘green dot’ illusion this is combined with the colour afterimage and is replaced by an illusory green circle.

Question 22

Waterfall illusion

Answer 22

An aftereffect of movement that occurs after viewing a stimulus moving in one direction. Viewing the waterfall makes other objects appear to move in the opposite direction.

Question 23

Spatial acuity

Answer 23

• Visual system
• The ability to distinguish two features that are very close together in space.

Question 24

Temporal acuity

Answer 24

• Auditory system
• The ability to distinguish two features that are very close together in time.

Question 25

Damage to V4

Answer 25

Causes achromatopsia (cortical colour blindness):
Person sees everything in shades of grey.

Question 26

Damage to V5

Answer 26

Causes akinetopsia (motion blindness)

• Bilateral.