Human Perception

Perceptual modalities (e.g. visual, audio; also called channels) have a short-term buffer that maintains a store for a few seconds. They can record details independent of human attention and deliberation.

The cycle time for perception is approximately 100 msec.

Visual channel

This is often the most relevant for designing user interfaces. The eye scan rate is approximately 230 msec per movement.

• Features
  • Color
  • Motion
  • Segment properties (e.g. horizontal, diagonal)
  • Location (generally stored separate of other features)
• Gestalt principles --- principles for defining objects and shapes
• Proximity
• Similarity
• Symmetry
• Continuity (alignment is a special case)
• Closure

See pages 18 - 21 for descriptions and examples.

• Attention
  • Only one locus of attention
  • Some features (e.g. motion) receive attention without a deliberate decision. With effort, these features can be ignored.
  • Some features (e.g. diagonal segments) can receive attention if the attention system is prepared to find the features.

Discussion

• How do Gestalt principles affect how users scan and understand web pages? Which principles are most relevant to interface design? Here are some for discussion:
• Yahoo Web site
• HCI Program Requirements
• Productivity tools (e.g. word, photoshop)
• Examples where status indicators are outside of the locus of attention
• What are the time profiles for different kinds of menu search:
  • Looking for exact text versus looking for general idea
  • New user versus repeated user