Midterm

Question 1

Confirmation Bias

Answer 1

a tendency of people to favor information that confirms their beliefs or hypotheses;

resulting from top-down or expectancy-driven processing, expecting a specific result skews a person’s perception

Question 2

Blind Spot

Answer 2

no rods or cones where the optic nerve leaves eye, blind spot is filled in by the brain

Question 3

Mental Model

Answer 3

A person’s schema of dynamic systems, typically include our understanding of system components, how the system works, and how to use it. Generate a set of expectancies about how it works and often vary on their degree of completeness and correctness

Question 4

Situational Awareness

Answer 4

“user’s awareness of the meaning of dynamic changes in their environment”, or “the perception of the elements in the environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future” p. 143

Question 5

Task Saturation

Answer 5

number of tasks being able to perform, as tasks rise so does performance up to the optimal point then performance drastically falls as tasks become too much (from memory, couldn’t find in book or slides)

Question 6

Bottom-Up Processing

Answer 6

What our senses tell us is there (stimulus driven)

Question 7

Top-Down Processing

Answer 7

Perception based on your knowledge (and desires) of what should be there (knowledge driven)

Question 8

Optic Flow

Answer 8

the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer and the scene

Question 9

Attentional Capture

Answer 9

salient stimulus dimensions designed to capture your attention when it is directed elsewhere

Question 10

Change Blindness

Answer 10

failing to notice a change in something due to its lack of salient stimulus characteristics, even though the change may be significant

Question 11

Ambient System

Answer 11

The system around you, whether it be light, temperature, sound, etc

Question 12

Focal System

Answer 12

Cognitive operating system in which information is obtained directly, i.e. the individual is attending to the cues (sort of the opposite of the ambient system)

Question 13

Visual Search

Answer 13

Series of eye movements used to detect a target in the visual field. Several models exist:

• Serial search: Sequential scanning of stimuli needed to detect target (attentive processes)
  
  • Search time increases with # of display elements
• Parallel search: Target “pops-out” of multi-element display without scanning (pre-attentive processes)
  
  • Search time constant, not affected by number of display elements
• Expectancy Effect: Search where we expect targets to occur, e.g., football quarterbacks, radiologists
• Availability Effect: search where it is easiest and most obvious (can overcome expectancy)
  
  • New drivers may not check mirrors because they are not obvious
• Saliency helps the search (draws our attention):
  
  • Motion/flickering
  • Bright/colorful (high contrast)
  • Large size (global)

Question 14

Cognitive Tunnelling

Answer 14

Occurs during troubleshooting. It’s the tendency to fixate on a particular hypothesis, look for cues to confirm it, and interpret ambiguous evidence as supportive.

Question 15

Cognitive Priming

Answer 15

Occurs when you match observed patterns to previous experiences; priming takes place on a subconscious, or “naturalistic” level

Question 16

Workload

Answer 16

The perceived demand placed on you by some task (it can be mental or physical); the workload depends on the amount of your total capacity that is being utilized, and so it’s dependent on your ability; workload for a given task will vary from person to person

Question 17

Cue

Answer 17

Information perceived by one or more of our senses (visual, audio, tactile, etc.) which enable us to make some inference (e.g. shadows and texture density are depth cues that inform us of how far away things are)

Question 18

Front End Analysis

Answer 18

first stage of human factors in the system lifecycle; purpose is to understand the users, their needs, and the demands of the work situation; usually accomplished by performing a user analysis, environment analysis, and function and preliminary task analysis (Ch.3-p.37, slide 38)

Question 19

Conceptual Design

Answer 19

second stage of human factors in system lifecycle (according to the slides); function allocation stage; assigning tasks to humans or machines taking into account capabilities and limitations of each while considering relative value, cost effectiveness, and cognitive/affective behavior (Ch.3- slides 38,60)

Question 20

User Centered Design

Answer 20

center the design process around the user by determining user needs and by involving the user at all stages of the design process (Ch.3-p.35, slide 37)

Question 21

Iterative Design

Answer 21

third stage of human factors in system lifecycle (according to the slides); evaluate design based on detailed task analysis followed by other activities such as interface design and prototyping, heuristic evaluation, cost/benefit analysis of alternatives, workload simulation and modeling, safety analysis, and usability testing (Ch.3-p.50, slides 38,61-64)

Question 22

Saliency

Answer 22

From the dictionary: prominent, conspicuous, or striking

one of the four factors of selective attention; salience is a bottom-up process, characterizing what is described as attentional capture (example: car horn capturing someone’s attention) (Ch.6-p.123, slide 7)

Question 23

Masking

Answer 23

when one sound is covered or “hidden” by another sound (Ch.5-p.96)

Question 24

Unitization

Answer 24

• Part of the analyzing perceptual process
• Is the transformation from analyzing individual, specific features to analyzing on a broader scale
• Example: Reading, as we get better at reading, we don’t need to look at every letter to read the word

Question 25

Perceptual Loop

Answer 25

• • Continuous process by which we perceive data and act on it
    
    • Perception (extraction of meaning from sensory inputs)
    • Recognition (understanding what the senses are perceiving)
    • Action (choosing to do something based on recognition of sensory inputs)
    • Environmental Stimulus (everything in the environment that can be perceived)
    • Attended Stimulus (stimulus in the environment that we are focused on)
    • Stimulus on Receptors (sensory receptors receive are stimulated)
    • Transduction (taking the sensory information and transferring it to the brain)
    • Processing (interpreting the information being sent to he brain from the sensory inputs)
    • back to Perception

Question 26

Phon

Answer 26

• Used as the units in equal loudness curves
• 1 phon = perceived loudness of a 1 db tone at 1000 Hz

Question 27

Just Noticeable Difference (JND)

Answer 27

The smallest detectable change that can be made to a stimulus where the change is noticeable

Question 28

Weber’s Law

Answer 28

JND = K(DI)/I

• K = constant for given stimulus
• DI = change in intensity
• I = absolute level of intensity
• The JND for judging intensity differnces increases in proportion to the absolute amount of intensity

Question 29

Chunk

Answer 29

• Unit of working memory space
• Chunks that form patterns or units may be combined into one chunk
• Example; four random letter, X D F L, would be 4 seperate chunks. However, DOOR would be one chunk.

Question 30

Affordance (Norman)

Answer 30

refers to the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used (a chair affords support and therefore sitting) p. 9

Question 31

Visibility (Norman)

Answer 31

the correct parts must be visible and convey the correct message, natural signals (doors that push/pull) p. 4

Question 32

Mapping (Norman)

Answer 32

technical term meaning the relationship between two things (controls and their movement) p. 23

Question 33

Natural Mapping (Norman)

Answer 33

taking advantage of physical analogies and cultural standards (control up, movement up) p. 23

Question 34

Knowledge in the Head (Norman)

Answer 34

internalized knowledge, often speeds up performance and task efficiency p. 189

Question 35

Knowledge in the World (Norman)

Answer 35

knowledge that is required for a task is explicitly available or readily derived from the situation p. 189

Question 36

Decision Making Task

Answer 36

It is a task in which:

(a) a person must select one option from a number of alternatives,
(b) there is some amount of information available with respect to the option,
(c) the timeframe is relatively long (longer than a second), and
(d) the choice is associated with uncertainty …”

Question 37

Recognition-Primed Decision-Making

Answer 37

A method of making a decision by which an individual recognizes that it is similar to some previous problem and applies or adapts the previous solution.

Question 38

List 5 Criteria for Good Alarms

Answer 38

1) alarm must be heard above background ambient noise;
2) alarm must not be above the danger level for hearing (if at all possible);
3) alarm should not be overly startling or abrupt;
4) alarm should not disrupt the perceptual understanding of other signals or ay background speech communication;
5) alarm should be informative, signaling nature of emergency and, ideally, some indication of the appropriate action to take.

Question 39

List the 3 Levels of Situational Awareness as Defined by Endsley

Answer 39

Level 1: combining the perception of elements in the environment within a volume of space and time;

Level 2: the comprehension of their meaning;

Level 3: the projection of their status in the near future

Question 40

List and Define the Primary Cues to Distance Perception

Answer 40

Accomodation – when an out of focus image triggers a change in lens shape to accommodate;

convergence – the amount of inward rotation the muscles in the eyeball must accomplish to bring an image to rest on the retina;

binocular disparity (or stereopsis) – depth cue that results from a larger disparity in images between the two eyes the closer an object is to the observer

(NOTE: the book doesn’t distinguish primary and secondary, so these are bottom up processing cues)

Question 41

List and Define the Secondary Cues to Distance Perception

Answer 41

linear perspective – the converging of parallel lines;

relative size – if two objects are the same size, the object with a smaller visual angle (more distant in a picture) is farther away;

interposition – nearer objects tend to obscure the contours of objects farther away;

light and shading 3D objects tend to cast shadows and reveal reflections and shadows on themselves from illuminating light;

textural gradients – any textured surface, viewed from an oblique angle, will show a gradient or change in textural density across the visual field

(NOTE: the book doesn’t distinguish primary and secondary, so these are top down processing cues)

Question 42

Provide a list of Cues which may be useful in driving Bottom-Up Visual Search Behavior

Answer 42

conspicuous targets are ones that “pop out” no matter where they are, so you don’t even have to look at non-targets. Cues with high conspicuity (attention grabbers) include flashing warning signals, moving targets, and uniquely colored or highlighted items (like in a checklist or book).

Question 43

Describe why our limited attentional resources might preclude us from serving as an accurate eye witness when being held up by a gunman.

Answer 43

Episodes are stored in long term memory, where they degrade and can be forgotten; may be influenced by outside sources (TV shows, what a criminal typically looks like), can experience biases (framing bias, expectancy bias, guilty bias)

Question 44

According to OSHA standards at what level must the employer provide hearing protection?

Answer 44

Employers must provide hearing protection if the time weighted average of sound intensity is above 85 dB.

Question 45

Why does OSHA provide separate exposure standards for continuous vs impulse sound?

Answer 45

If you are only exposed to a loud noise for a short amount of time, you will have a higher threshold of pain and hearing loss for that intensity level than if you were exposed to it continuously. That’s why OHSA uses the time weighted average, to address the tradeoff between time and intensity. They convert the varied time history of noise exposure into a single equivalent standard.

Question 46

What does the vestibular system have to do with motion sickness?

Answer 46

The vestibular sacs and canals are located in the inner ear, and they possess receptors for angular and linear acceleration. These can cause motion sickness when a person in a vehicle cannot see where he or she is going but perceives the acceleration via those inner ear receptors. When the vestibular cues signal motion but the visual world does not, it leads to a decoupling of the two channels, which can cause nausea or other discomforting sensations.

Question 47

Fill in the blanks. “Modern Human Factors Understands that People use technology to accomplish their _______ in their _____________.”

Answer 47

goals or tasks, environment

Question 48

List 3 reasons we might decide to apply 3D sound in an operational environment

Answer 48

• • Improving performance (response time)
  
  • o Eyes only cover about 130-degree range, ears are 360; 3D sound helps narrow the search area quickly
• • Managing attention
  
  • o Helps determine which audio information to focus on when receiving multiple messages, e.g. air traffic controller hears a different message in each ear relative to location of the aircraft, tunes out the less critical one
• • Reduces effort
  
  • o Operator doesn’t have to divert as much attention resources to visual scanning because the directionality of the audio cues will enhance his or her situational awareness

Question 49

A study was conducted in which 10 people were each asked to use 3 unique prototypes of a new software package. Was this study a within, between, or mixed experimental design?

Answer 49

Within-subjects; each prototype was assessed using the same group of people

Question 50

Why might one decide to design a mixed-subject experimental design?

Answer 50

Each independent variable in the experiment can be either between-subjects or within-subjects, and there are often advantages to using one or the other type of design for a given variable. If you wished to evaluate the influences of several variables at the same time, of which some were better for within- and others for between-subjects, you would design a mixed-subject experiment.

• An example would be where subjects must receive one type of training (e.g. via a simulator) and they cannot go over it again for another type because they already know the material, so training is between-subjects. Now if you also want to measure the effects of environmental distractions on their training, you would have both groups endure the same distractions, which would be a within-subjects variable.

Question 51

List Norman’s Seven Design Principles and give an example of how each of these principles might be applied in design of a driver’s interface to an automobile.

Answer 51

1. Use both knowledge in the world and knowledge in the head (models and manuals)
o Design the cruise control lever so that pushing up accelerates and pushing down decelerates (fits our mental model/intuition), but also include this in the manual in case someone still can’t figure it out).
2. Simplify the structure of tasks
o Reduce mental load by automating certain tasks, e.g. install photo-sensors such that the headlights come on automatically when it’s dark without requiring the driver to activate them manually.
3. Make things visible … bridge the gulfs of Execution and Evaluation
o Include an icon on the driver’s display that lights up when cruise control is turned on (as opposed to simply a switch of button that remains depressed when it’s on). That way the driver receives confirmation that the CC has been activated.
4. Get the mappings right
o Locate the controls for the car stereo directly beneath the input for the CD player, MP3 player, etc.
5. Exploit the power of constraints, both natural and artificial
o Do not allow the key to be removed from the ignition until the car’s transmission is in the “park” position (applies to automatic transmissions). This will prevent the car from rolling away if the driver exits without applying the emergency brake.
6. Design for error
o Allow activation of four-wheel drive while the vehicle is moving (some older vehicles required coming to a stop first). That way if the driver forgets to turn it on before beginning to drive and then is unable to stop and pull over because he or she is on a busy highway, it can still be activated later.
7. When all else fails … standardize!
o For devices like the windshield wiper and the cruise control device where there is no great natural mapping, locate them in the same place and with the same functionality as other existing automobiles at that time.

Question 52

What are the four steps which are accomplished through a Front End Analysis?

Answer 52

1. User analysis (who is the user?)
2. Environmental analysis (what environment will the product/system be used in?)
3. Function and task analysis (major functions/tasks to be performed by the system/person/machine?)
4. Identify user preferences and requirements

Question 53

Why might the mental model of the designer and the user be different and how does this knowledge affect the design process?

Answer 53

A user might not have the same knowledge or expectancies of how a system should work compared to a designer. Designers should create designs that are consistent and compatible with the population stereotype (p.137). Designers should create personas that represent user population to prevent the natural tendency to assume users are like themselves (p.38).

Question 54

Three lights, one red, one green, and one blue are activated at the same intensity measured in Watts. Which of these will appear the brightest and dimmest to a user?

Answer 54

Green – brightest
Blue – dimmest
(http://www.physicsclassroom.com/class/light/u12l2b.cfm)

Question 55

A sign is illuminated such that the letters reflect light with a luminance of 1000 cd/sq m and the background around the letters reflect light at 720 cd/sq m. What is the contrast ratio for this sign? Given this contrast ratio, would you expect the sign to be clearly legible? Why or why not?

Answer 55

No, because the contrast ratio should be at least 3:1 (best at 4:1) – (Ch.4 slide 32)

Question 56

Name at least 3 considerations you should make when selecting colors during a user interface design.

Answer 56

• Are there any visual problems that may make the information less legible (aging, color blindness, improper illumination)? (Ch.3-p.73, slide 41)
• Does color add something that cannot be provided by black and white? (Design for monochrome first with color used as redundant backup)
• Is the chosen color appropriate for the text or object?
• Does the color provide cues to improve understanding or memory?

Question 57

List 3 reasons you might decide to present something visually as opposed to auditory.

Answer 57

• If the environment has a lot of noise where the message could potentially be masked (p.96)
• If you want the user to focus on a certain locality—visual signal has more precision that sound localization (p.103)
• If you want to present spatial information, like the layout of a city on a map

Question 58

List 3 reasons you might decide to present something auditory rather than visually.

Answer 58

• If there is improper lighting in the environment (p.73)
• For alarms, an auditory system is preferred since it is omnidirectional, in other words, we can sense auditory signals no matter how we are oriented (p.97)
• If it is important for someone to maintain eye contact on their environment, an auditory message would be better rather than have the user look away at a visual message.

Question 59

Why might a resident be more likely than a full physician be more likely to see an unusually placed tumor in a radiograph?

Answer 59

A full physician will be more likely to see abnormalities because he/she would look more closely at areas of an x-ray most likely to contain a tumor. This expectancy is a top-down, knowledge driven factor that develops from training and experience.

Question 60

According to multiple resource theory, if an air traffic controller’s primary task was to scan a display for incoming enemy aircraft, why might you want to provide a chemical alert using something other than a flashing light?

Answer 60

• Using an alert similar to that of the display would make it easier for the controller to miss it. Using a chemical alert would activate another sensory input making it easier to notice the alarm.

Question 61

Name three implications of long term memory limitations for the design of a product.

Answer 61

• Encourage regular use of information to increase frequency and recency
• Encourage active verbalization or reproduction of information that is be recalled
• Standardize
• Use memory aids
• Carefully design information to be remembered
• Design to support development of correct mental models

Question 62

When discussing situational awareness errors, Endsley discusses four primary error sources. List these four sources and provide an example for each.

Answer 62

• e1 – system may not access all important information (system may not show all data from the real world)
• e2 – Not all of the information available to system is provided to the user (interface is not able to show all of the data in the system)
• e3 – Not all information displayed is perceived by the user (operator does not understand all of the data from an interface)
• e4 – The user might have limited ability to perceive the real world (operator may not understand everything going on the real world environment)

Question 63

What are the three phases associated with decision making?

Answer 63

• Acquiring and perceiving information or cues relevant to the decision
• Generating and selecting hypotheses or situation assessments about what the cues mean
• Planning and selecting choices to take

Question 64

What are biases in cue reception?

Answer 64

• Attention to a limited number of cues
• Cue Primacy and Anchoring, first cues given more weight and affect decisions more than later cues
• Inattention to later cues
• Cue Salience (flashing, audible, etc)
• Overweighting Unreliable Cues

Question 65

What biases exist for hypothesis generation?

Answer 65

• Limited number of hypotheses generated – people consider only a small subset of possibilities
• Availability heuristic – people make judgments based on how easily information is retrieved (e.g., risk of airplane crash)
• Representativeness heuristic – decision based on how closely info represents typical outcome
• Overconfidence – individual’s belief that they are correct more often than they actually are

Question 66

What are biases for action selection?

Answer 66

• Retrieve a small number of actions – limited by how many action plans can be held in working memory
• Availability heuristic for actions – easy to retrieve actions are most often chosen
• Availability of possible outcomes – decisions will be made based on how memorable the outcome of that choice has been in the past
• Framing bias – manner in which problem is phrased affects decision
  - Ex: decision to have surgery affected by whether told you have a 70% chance of living or 30% chance of dying
  - Sunk costs
  - Frame decisions in terms of gains to counteract tendency