Lec4 - Visual Perception

Question 1

What is Gestalt vision?

Answer 1

• Human vision biased to perceive structure (whole shapes, figures and objects) - a unified whole
• Given a visual image the human brain chooses the simplest interpretation

Question 2

List some examples of Gestalt principles

Answer 2

• Emergence - seeing the big picture (perceiving the whole)
• Closure - seeing the complete shape - mind fills in the gap
• Continuity- Grouping elements that follow the same path (seeing a continuous shape)
• Proximity- Objects that are closer together are perceived as a group
• Similarity- Objects sharing visual characteristics are perceived as a group
• Common Region- Objects in the same region are perceived as a group (aka Enclosure)
  -Figure/Ground- Brain separating foreground from background. More attention given to foreground. Separation supported by contrast, brighter, crisper objects perceived as in front

Question 3

What are Gestalt principles and what are they used for in design?

Answer 3

• They are how we see structure in visual stimuli
• In design they guide the layout of user interfaces and information to effectively communicate structure.

Question 4

Why is visual structure important?

Answer 4

• Helps us scan and understand information quickly
• Good spacing, grouping and alignment all reduce search time

Question 5

What is preattentive processing?

Answer 5

• Performed automatically on the entire visual field. Done quickly and in parallel without focusing visual attention
• Preattentive processing is when information is gained in less than 200-250ms. Relying on peripheral vision. It’s the process of completing certain tasks with our peripheral vision

Question 6

What is attention guidance?

Answer 6

• Preattentive processing draws our attention and directs foveal vision.
• Applying this can direct attention to critical information thus conveying information at a glance thus attention guidance

Question 7

What are pop out features?

Answer 7

• Aka preattentive features
• visual properties perceived without focussed attention (e.g. colours (stronger than shape) and shapes)
• They help communicate information efficiently
• some can convey quantitative information (e.g. length, size, position and orientation)

Question 8

What are the different types of data and what perceptual channels can we use to represent data visually?

Answer 8

Data types
- Nominal - data in categories
- Ordinal - data in order (e.g. 1st, 2nd, 3rd)
- Quantitative - variables have magnitude (e.g. the metric system)

Perceptual channels
- Position
- Size
- Colour, brightness
- Shape

Question 9

What are some types of visual encoding?

Answer 9

Position
- encodes quantitative variables

Colour value
- Lightness perceived as ordered (encodes ordinal data)
- Less good for encoding continuous variables (contrast better)

Colour hue
- Perceived as unordered
- Encodes nominal data
- Not always a good idea to use for a scale