HCI Flashcards
1
Q
Fovea
A
- Central area of retina packed with cones for sharp, high-detail colour vision
- Covers only about 1 degree of visual angle
- Less than 1% of the retina’s area but more than 50% of the visual cortex’s neurons
2
Q
Periphery
A
- For movements and greyscale contrasts
- Contains mostly rods but has cones
3
Q
Retina
A
- Has 6 million cones for high-accuracy colour vision
- Has a blind spot which the optic nerve passes through
4
Q
Gestalt Principles
A
1) Simplicity
- Perceive stimuli in a way that is regular, symmetrical and simple
- Eliminate complexity and
unfamiliarity to create meaning
2) Proximity
- Nearby stimuli are grouped
3) Similarity
- Similar stimuli are grouped
4) Figure and ground
- Tend to see a figure on a ground
- Can be ambiguous
5) Focal point and salience
- Often achieved by dissimilarity
- Used as a means of guiding user
5
Q
CIE Colour Space
A
- Contains all visible colours
6
Q
Additive color system
A
Colours are mixed by adding up primary colours (RGB)
7
Q
Subtractive color systems
A
Colours are mixed by subtracting complements of primaries from white (CMYK)
8
Q
Voluntary eye movements
A
Used to track objects
- Fixation: holding gaze stationary (0.1 - 1s)
- Saccade: jump to new gaze target (<0.1s)
- Smooth pursuit
- Vengence shift: looking at a point closer/further
9
Q
Involuntary eye movements
A
Enhance vision and prevent eye fatigue during fixations
- Microsaccade: small jump
- Drift: slow, roaming movement
- Tremor: fast, small oscillation (about 90 Hz)
10
Q
Cognitive processing time
A
Between 70-300ms
11
Q
Low Fidelity Prototype
A
- Uses a medium unlike the final medium
- Quick, cheap and easy to change
- Examples: sketches of screens, task sequences, post-it notes, storyboards
Advantages:
- Low development cost
- Evaluates multiple design concepts
- Useful communication device
- Addresses screen layout issues
- Useful for identifying market requirements
- Proof of concept
Disadvantages:
- Limited error checking
- Poor detailed specification to code to
- Facilitator driven
- Limited utility after requirements established
- Limited usefulness for usability tests
- Navigational and flow limitations
12
Q
High Fidelity Prototype
A
- Looks like or more like the finished product
- Provides demonstration of functionality
- Example: dynamic wireframe
Advantages:
- Complete functionality
- Fully interactive
- User driven
- Clearly defines navigational scheme
- Use for exploration and test
Disadvantages:
- More resource intensive to develop
- Time consuming to create
- Inefficient for proof-of-concept designs
- Not effective for requirements gathering
13
Q
Users for designing a new interactive system
A
- Those who interact directly with the product
- Those who manage direct users
- Those who receive output from the product
- Those who make the purchasing decision
14
Q
Direct manipulation examples
A
- Using a mouse to move a file on a desktop
- Using a gesture to open an app
- Using digital blocks to compose music
- Kicking your foot to open the boot of a car
15
Q
Requirements
A
- Requirements often need clarification, refinement, completion, re-scoping
- They can change during the course of a project
- There are functional and non-functional requirements, both of which are important for a system
16
Q
Use cases
A
Provide a step-by-step breakdown of the interaction between a user and a system
17
Q
Troxler’s Fading
A
The lilac discs tire out the red and blue cones, so green cones dominate when a disc is removed and a green afterimage appears. After a while the green afterimages cancel out the lilac disks
18
Q
Student’s t-test
A
- The two most frequently used types of t-test
- Calculates the likelihood of a difference between two sample means given that they are from the same population
- One-tailed test is used for a directed hypothesis
- Two-tailed test is used for an undirected hypothesis
19
Q
Motion parallax
A
- Motion parallax, simulated using head tracking
- Defocus blur, simulated using foveated rendering
20
Q
Binocular depth cues
A
- Stereopsis and convergence
- These can be simulated using stereoscopy
- Horizontal human FoV: 210°
- Vertical and horizontal 3D FoVs: 150° and 120° respectively
21
Q
Immersion
A
Replacing real-world sensations with virtual sensations
22
Q
Presence
A
Sensation of being there, as a result of immersion
23
Q
Contextual Inquiry
A
- Interview while being observed
- Users involved in contextual inquiry are observed and questioned while they work in their own environment
- Four principles:
1) Context
2) Partnership
3) Interpretation
4) Focus
24
Q
PCCR
A
- Stands for Pupil Center Corneal Reflection
- Often in combination with head and face tracking or other glints to determine eye distance from tracker
- The accuracy is limited by fovea (about 0.5 degrees), eye movements (during fixtation), calibration and hardware limits
25
Eye-gaze controlled UIs
Challenges faced:
1) Size of the fovea
2) Involuntary eye movements
3) Midas touch
4) Problem of how to click
26
Cognitive processes
- Attention
- Memory and working memory
- Reasoning
- Knowledge
- Comprehension and production of language
- Judgement and evaluation
27
Nielsen's 10 Usability Principles
- Visibility of system status
- Match between system and the real world
- User control and freedom
- Consistency and standards
- Error prevention
- Recognition rather than recall
- Flexibility and efficiency of use
- Aesthetic and minimalist design
- Help users recognize, diagnose, and recover from errors
- Help and documentation
28
Fitts Law
- Predictive model of human movement
- A function of the ratio between the distance to the target and the width of the target
- Used to model the act of pointing
- The original formula has been modified to take different input devices into account
ID = a + b.log₂(A/W + 1)
29
Sharp, Rogers and Preece
- Affordance
- Constraints
- Visibility
- Feedback
- Consistency
- Mapping
30
Color blindness
- Red-green is the most common form
- Mostly affects males
31
Task analysis
- Used to obtain descriptions of what people do
- Links actions and objects to make up procedures
- Criticised for being divorced from people's situation of work
- Allows for maximum positive transfer of users' existing knowledge
32
Null hypothesis
There is no difference or difference in another direction from what was expected
33
Alternative hypothesis
There is a difference in a certain direction
34
Testing hypotheses
p ≤ α:
- Reject null, accept alternative
- However could make a type I error ("false positive")
p \> α:
- Accept null, reject alternative
- However could make a type II error ("false negative")
35
Design patterns
- Describes a solution to a problem in a certain context
- Capture design experience, but that doesn't necessarily mean good design
- Web design patterns include pagination and lazy registration
- There are design patterns for specific types of user interfaces, such as the web and mobile apps
36
Main tasks for collaboration
- Communication
- Cooperation
- Coordination
37
Variables for classifying collaborative system
- Time
- Place
38
Norman's Theory of Action
Stages of Execution:
1) Establishing a goal
2) Forming an intention
3) Specifying an action sequence
4) Executing the action
Stages of Evaluation:
5) Perceiving system state
6) Interpreting system state
7) Evaluating system state wrt goals and intentions
39
Common ground
- Allows design teams to establish a set of commonly agreed terms
40
Norman's Conceptual Framework
Makes explicit the relationship between:
1) How a system should function
2) How it is presented to users
3) How it is understood by them
41
Norman, Ortony and Revelle's Model of Emotion
- Visceral
- Behavioural
- Reflective
42
Usability Testing
- Often includes think-aloud protocol
43
Quantitative methods
- Usually produce data in the form of numbers
- Can be combined with qualitative methods fairly easily
44
Qualitative methods
- Usually produce data in the form of text
- Can consist of think-aloud protocols
45
Independent variable
- The variable of which we want to know the effect
- Levels = the different values to try out and compare, which lead to conditions that need to be tested
46
Dependent variable
- Variable that describes the effect being investigated
- Needs to be measurable as accurately as possible
47
Anti-pattern
Illustrate solutions with bad usability that designers should avoid
48
Anthropomorphism
The use of characters with human-like properties
49
Threats to validity
1) Misunderstandings
2) Order bias
- Means that the order of tasks has an effect on measurements
- Counter-balance task order to distribute the bias
3) Training Effect
- Training phase before each type of tasks
- Counter-balance task order to distribute effect
4) Fatigue
- Participants get tired after hard tasks
- Schedule breaks after every n tasks
- Counter-balance task order to distribute effect
5) Social Desirability Bias
- Participants tend to do what is socially expected
6) (Self-)Selection Bias
7) Confounding Variable
- Variable that is not controlled, but has an effect
50
Social Desirability Bias
Means participants tend to do what is socially expected
51
Binaural hearing
- Delays and attenuation give clues as to the sound position
- Model does not account for symmetrical lateral positioning
52
HRTF
- Stands for head-related transfer function
- The ratio of pressure at
the ear to pressure at the
centre of the head
For synthesising HRTF:
1) Capture head mesh using
laser scanner
2) Compute the waveform as it propagates, this avoids the need for the anechoic chamber
53
Guiard's Model of Bimanual Skill
- Humans are not only two-handed, they use their hands differently
- A non-preferred hand:
1) Leads the preferred hand
2) Sets the spatial frame of reference for the preferred hand
3) Performs coarse movements
- A preferred hand:
1) Follows the non-preferred hand
2) Works within established frame of reference set by the non-preferred hand
3) Performs fine movements
54
Defining Tasks
They must be:
1) Relevant
2) Well-defined
3) Realistic
4) Variations
5) Well-timed
55
Remote eye gaze tracker
- An infrared illuminator is used to create a reflection on the cornea
- The vector between the pupil and that reflection gives an indication where the user is looking at
56
Theory of Reasoned Action
1) Attitude (individual evaluation of a behaviour)
2) Subjective norm (how society or environment contributes to
behaviour)
3) Intention (indication of an individual's readiness to perform a given behaviour)
4) Behaviour (observable response in a given situation with respect to a given target)
57
Theory of Planned Behaviour
- Perceived behavioural control (the extent to which the individual believes they can control behaviour)
- Beliefs about whether factors that will affect the difficulty of the behaviour
- Perceived power of these factors
- Number of factors
58
Microsoft Clippy
- Had an intelligent user interface
- Was disliked by many, regarded as annoying, distracting, patronising, intrusive
