Psychology of usability

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 12345 OK Code: Name: A Company Old countryroad Address: 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:MemoryEmotionsMovement Working memory Audition Action Vision Mechanicalsenses: touch, pain Body state (hunger, vestibular sensation, etc.)

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