7: Human Abilities

Question 1

How does vision work

Answer 1

• Colour is sensed by cones, mostly in the centre of the retina.
• 3 types of photopigments used to sense colour, blue, green red that are sensitive to different bands of spectrum. Not even distributed. 64% red, 4% blue. Humans are most sensitive to the centre of the colour spectrum.
• Different wavelengths of light focused at a different distance behind the eye lens
• human less sensitive to blues and reds, blues and reds must be made brighter to be seen as the same vs green and yellows. Blue may be harder to see as age increases.
• red and green should not be used at the edges
• saturated colours require focusing and should not be used.

Question 2

How does hearing work

Answer 2

soundwave enters the outer ear, travels through the ear canal and to the eardrum.
the eardrum vibrates from the soundwave, vibration travels to the tiny bones –> vibrate fluid –> connected nerve –> send signal to audio image store

Question 3

How does touch work

Answer 3

2 components of haptics

1. cutaneous:
   
   • sense based no skin receptors
2. kinesthesia:
   
   • perception of limb movement, position
   • perception of force
   • sense based on muscles, joint, tendons

Question 4

What are the implications of the ability limits due to old age?

Answer 4

Hearing:

• The average human has a hearing frequency range of 20Hx to 20KHz.
• Can tell the difference 1.5Hz.
• Hearing loss occurs at age 50, 14KHz and 70,10KHz
• Older people cannot hear higher frequencies so
• Sounds used should not be too high pitched.

Vision:

• ageing may cause the lens to turn yellowish
• further hindering perception of blue

Question 5

What are the implications of the ability limits due to human disabilities?

Answer 5

colour blindness –> difficult to discriminate the difference between certain colours. For most colour blindness, it is hard to see the difference between greens and reds of blues and purples.

implications:
avoid use of colors dependent of red and green
color blind that has a different colour scheme all together

Question 6

How do you overcome these human disability limits during the UI design?

Answer 6

implication –>
- do not use colours only within the design, certain combinations of colours should be avoided

• use a combination of colours, symbols, patterns and textures
• use text labels of images and buttons

Question 7

What is the Model Human Processor? Why is it useful in HCI?

Answer 7

MHP is a representation of psychological knowledge about human performance based on task analysis, calculations and approximations.
The model consists of a set of memories and processors with three interacting subsystems, the perceptual system, the motor system, the cognitive system.
It is useful as it can be used to make predictions on human performance or compare user interfaces.

Question 8

Explain perceptual causality and give examples

Answer 8

2 distinct stimuli can fuse if the first event appears to cause the other event.
- lip-synching

Question 9

How does memory work?

Answer 9

1. working memory(short term)
   - small capacity(7+- 2 chunks)
   - contains visual image store
   - rapid access of 70ms, decay of 200ms
2. Long term memory
   - huge if not unlimited storage
   - slower access time of 100ms with little decay

Question 10

What are the implications of the limitations of memory?

Answer 10

Create cognitive chunks in UI design

Question 11

What is Cognitive Load?

Answer 11

The amount of information that the working memory can hold and handle at a time.

1. intrinsic load
   - level of difficulty with specific instructional topic
2. extraneous load
   - manner in which info is presented
3. germane load
   - processing, construction of patterns

Question 12

What are the main effects of cognitive load?

Answer 12

1. split attention
   - multitasking
2. redundancy effect
   - information presented in a format with both diagrams and accompanying text
3. element interactivity
   - instructional content composed of elements
   - elements may interact if there is a relationship
   between them.
   - eg. yellow coloured red etc..

Question 13

How do you overcome these limits of memory during UI design?

Answer 13

cognitive chunking, colours, whitespace to reduce cognitive load. Recognition rather than recall –> activate long term memory –> cues activate the memory of what to do