7. Perception and Visual Patterns

Gestalt Laws

• the whole is different from the sum of its part
• leaving a set of descriptive principles, without a model of perceptual processing.

The Principle of Pragnanz

• Fundamental principle of gestalt perception
• Law of simplicity, law of good figure
• tend to order our experience in a manner that is
  • Regular
  • Orderly
  • Symmetric
  • Simple

Principles

1. Emergence
   1. the dog is perceived as a whole. (without explicit edges)
2. Reification
   1. more explicit spatial experience
3. Multistability
4. Invariance

Gestalt Principles

Grouping

1. Proximity: associated with nearby elements

2. Similarity: associated with similar elements

3. Continuity: Preference for continuous, unbroken, smoothest contours with the simplest possible

4. Common Fate: things moving together

5. Closure

6. Common Region

7. Connectedness

Perception of Form

1. Closure: form complete, closed figure increase regularity
2. Area/Figure and Group/Relative Size: smaller one is figure
3. Symmetry: we tend of perceive objects as symmetrical shape in spite of distance

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Gestalt Laws can mislead

→ Natural Camouflage

Examples

Grouping

helping users parse the display into subunits

→ 2D space에 data가 품고 있는 구조, dimension을 파악 후 mapping한다.

Hierarchy

provide a context for each piece of information

→ similarity, proximity

e.g. mac vs windows

Data 간의 Hierarchy가 실제 data 구조, 디자인과 잘 맞아야함

Balance

harmonious global arrangement.

→ visual weight를 고려하여 디자인.

modal에서 오른쪽 아래에 confirm 버튼 넣기

Human Size Perception

• Straight line > Curved line > Sharp line

즉, curved line, sharp line은 좀 더 과장해서 그려야 visual weight이 맞아진다. (optical adjustment)

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Human Visual System

• Visual attention: mechanisms that help determine which regions of an image
• Detailed vision for shape and color → foveal vision (약 1도)
• Motion은 주변시야에서도 감지 가능
• Fixation-saccade cycle

Fixation-Saccade Cycle

• Fixation: 자세한 정보가 필요할 때 잠깐 멈추는 period
• Saccade: 새로운 location으로 이동할 때 flicking하는 것.
• Bottom-up: information from fixation → mental experience
• Top-down: current mental states(task and goals) → Guiding saccade.

Expectation and memory

Current state는 아주 중요한 역할을 한다.

• Role of memory and expectations.
• 무엇을 기대하고있는지에 따라서 해당 물체나 장면에 대해 기억하는게 달라짐.

Preattentive Tasks

Postattentive Amnesia

Previewing do not make search faster!

human vision is not optical camera.

→ Postattentive search was as slow as traditional search.

그래서 결국 시각화 디자인에 적용하려면…

• 대부분의 시각화는 novel하다. (대부분 처음보는 chart일 것이다)
• LTM으로 콘텐츠가 commit되기 힘들다.
• preattentive methods가 data exploration에 있어서 매우 중요하다.

Preattentive Tasks

• low-level, fast-acting visual process에 의해 빠르게 감지되는 시각적 feature
• Precede focused attention
  • within a single fixation

1. Target detection
2. Boundary detection
3. Region Tracking
4. Counting and estimation

→ Motion is very preattentive. (retina 영역에 있어도 detect가능). Unintended attention

Laws of preattentive display

1. 간단한 차원에서 stand out해야한다.
   • color
   • simple shape
   • motion
   • depth
2. lessons for highlighting → 섞으면 안됨

각 channel 마다 더 overrule하는 게 있음

when mixed, hue » shape

hue « brightness (which I disagree)