1. Psychology of usability
User interfaces
Jaana Holvikivi
EVTEK

2. Usability goals
International Standards Organization ISO 9241 definition:
Usability is the effectiveness, efficiency, and satisfaction with which users can achieve tasks in a particular environment of a product. High usability means a system is easy to learn and remember; efficient, visually pleasing and fun to use; and quick to recover from errors.
Effectiveness: can users successfully achieve their objectives?
efficiency: how much effort and resource is expended in achieving those objectives?
satisfaction: was the experience satisfactory?

3. Universal usability Variations in physical abilities, disabilities
Variations in use environment
Diverse cognitive abilities
Diverse perceptual abilities (vision, hearing)
Personality differences
Cultural and international diversity
Special user groups: children and the elderly

4. Related fields Engineering psychology Ergonomics Experience design
Human-centered computing
Human computer interaction (HCI)
Industrial Design
Systems engineering
Ubiquitous computing
User-centered design
User experience design

5. Ease to learn in interface design
Familiarity in interface
Observations and patterns
regular shapes
proximity
continuity
recognition
grouping
Logical structure

6. Grouping features - colors, size, shape prototypes, schemas
internal consistency & similarity in a group
logical, conform with reality
sparse (not too many categories)

7. Regular shapes
vision / perceptions simplifies and groups things together
5 circles (not 9 parts)

8. Proximity

9. Similarity

10. Continuity

11. Familarity

12. Connectedness

13. Object - background

14. Balance
size
color
dark colors heavy
position
proximity
do these move?

15. Creating forms Left-aligned Vertical alignment of texts
Items that repeat in the same position
Chunking & grouping
Regular size input fields

16. Grid for forms Code: 12345 OK Name: A Company Address: Old countryroad
02650
Esbo

17. Efficient dialogue 6..15 groups neat layout use of space
experienced user prefer dense forms
novices prefer less crowded boxes

18. Fastest spotting of items

19. Mediocre spotting of items

20. Human perception: sees patterns
People can discriminate color and lighting
Object and background
Borders and continuity
Shapes and interpretations
People remember even large chunks
Football teams: colored shirts

21. Shades
source of light
concave and convex

22. Interpretation

23. Interpretation
Müller-Lyer -illusion

24. Background

25. Colors Help in recognition
Have emotional values and symbolic meanings - warning
Warmth
Color blindness common

26. Background

27. Human cognitive capacity 1
Based on patterns and schemas
Chess masters remember nearly all pieces in a game
Affordances: visual object is perceived through intended action; perception depends on context
Auditive and visual input separate

28. Human cognitive capacity 2
Attention: selective perception
Object and background: discrimination, exceptional features
Attention is directed to one object
Memory registers also unconscious perception
Automatic actions (bicycle riding) do not need attention; but then action becomes fixed, difficult to modify (changes in interface)

29. Modalities: perception
Chemical senses: Smell, Taste
Brain
Stored experience: Memory Emotions Movement
Audition
Working memory
Action
Vision
Mechanical senses: touch, pain
Body state (hunger, vestibular sensation, etc.)

30. MEMORY Long term or Reference memory Short term memory Sensory memory
Working
memory
Declarative
memory
Precedural memory
Central
executive
Modalities
Semantic
memory
Episodic
memory
Motor
skills
Perceptual
learning
Conditioning
Habituation and
sensitation
Recognition
Recall