DOET Chapter 1Models, Modes, Execution and Evaluation

ITEC4130Dr. Jim Rowan

Today’s Question:

• Name the two Gulfs discussed by Don Norman

Stuff in the world

• DVDs• Cell phones• Automobiles• Student IDs with RFID chips• Turn arrow at PepBoys on JimmyCarterBvd

Poorly designed objects

• Difficult to use• Don’t provide clues as to their use

• EVEN WORSE: Provide false clues.

• Have hidden modes of operation• Generally unpleasant to use, unfriendly…

Well-designed objects

• Easy to interpret• Easy to understand• Provide clues as to their use

Why does this happen?(My personal opinion: Up for

discussion)• For objects in the natural world: form follows function

• For objects in the man-made world form can be completely disassociated from function

• Made worse by the transition from the mechanical to the electronic– Mechanical objects are visually inspectable– Electronic objects are NOT visually inspectable

The glass door trap

Design principle:Visibility and the

GlassDoors• Correct parts must be visible

– If they aren’t how do you know what to do?

• Parts must convey the correct message– Mappings: Does what the object tells you about how to use it (through the parts it shows you) match your expectations of those parts?

Hidden mappingsThe Leitz slide

projector control

• Only one button but two operations

• Not designed for intuitive use• Not designed for explorative use either– Does it violate Norman’s Visibility?– Does it violate Norman’s Mapping?

The phone example in book

• Instructions were written in the language of the designer not the language of the user

• The hold function lacked results visibility:– Was the call I just put on hold actually put on hold or was it disconnected?

– Other phones flash a light beneath the hold button (at least it connects the flashing light to the button that activated it)

The phone• Did you know…

• Dial tone was an intentional addition– Made the invisible (do I have a connection?) visible

– It tells you that you can start dialing

Norman’s Principles

• Visibility• Appropriate clues• Feedback of one’s actions

Affordance and Causality

• The perceived and actual properties of a thing that determines how it is used.

• Affordances are strong clues.• Correlation does not imply causation

– Though as humans we REALLY want it to!

• Temporal correlation implies causality– Can give rise to superstition

Affordance and Causality

• For push buttons (especially the remote)– Sometimes they click– Sometimes a light flashes

• The lack of expected temporal correlation gives rise to repeated action– Like an idiot, you keep pushing the button hoping to eventually get something to happen

– You end up causing an error… or deleting an entire season of CSI!

Projected keyboardsWhy?

You don’t have to carry them with you!

Projected keyboards…

• What are the problems?• my answers next slide

Projected keyboards…

• fingers block the display

• no audible click (can be added with software

• no physical movement• no physical feedback on finger positioning

• room lighting

Projected keyboards…

• Possible partial solutions?• my answers next slide

Projected keyboards…(partial solutions)

• software generated “click”• the typed word appears on the screen

• What about solving the finger position problem? (not so easy)

Tiny keyboards…affordance issues

• Problem:• fingers hide keyboard?

• show the selection larger

Where do user expectationscome from?

• Some are cultural• Some are explicitly learned (standards)– cold water is on the right– hot water is on the left

• Some may be basic to humans– The attraction of the campfire…– The beauty of the arch as a basic form…

Clues from visible structure

• Affordances• Constraints• Mappings

• Consider scissors– Holes in the handles afford insertion– Hole size constrains what can be inserted (fingers, maybe; legs, probably not.

Models, Mental and otherwise

• Three different models– Design model: The designer’s conceptual model.

– System image: The model implied by and presented by the device’s structure

– User’s model: The mental model you hold that guides your actions

Models, Mental and otherwise

• Consider the refrigerator– the visible controls (the system image) imply two separate systems

– in actuality it is only one system

• Errors arise when the user (using his mental model implied by a flawed system model) tries to operate the system

But: Who’s Model is it really?

• The designer has a model when creating a device

• The user has a model when trying to use a device

• The system image is how the designer communicates with the user; It’s the device’s physical and operational form.

• You (as the designer) are most probably NOT the user so you’d better know the user!

Hidden Mode Problems

• A mode is a change in context that affects the interaction with a device.– A button means one thing in one mode and something different in another mode

• Many features with few controls give rise to hidden modes– “featuritis”

• Modes must be made visible

Hidden Mode Problems

• Airbus 320 was a mode problem– pilot was doing a flyby– the airplane was doing a landing

• Flying into the Everglades:– A tale of human attention/distraction– Going off autopilot was silent

The Good

• Visibility• Natural mapping from control to controlled

• Feedback• Number of controls = number of functions– or make certain the modes are visible

The Bad

• Hidden modes• Arbitrary mappings

– The forklift!

• False conceptual model– The refrigerator

• Many functions, few controls– cell phones

Natural Mappings

• Relationship between controls and actions are apparent to the user– Spatial analogy: Up on the control is up

– Cultural or biological (rising level is more)

– Additive (loudness, brightness)– Substitutive (increasing pitch is more)

Feedback: Good!

• Tactile feedback (keyboards… )

• Auditory feedback (keyboards, phones…)

• Visual feedback (pencil, changing lights…)

Why are there so many bad designs?

• Multiple stakeholders in a design venture– Designer– Manufacturer– Retail outlet– Purchaser– Maintenance

Technological Paradox

• Technology provides more functionality; possibly reducing the number of devices needed

• More functionality increases complexity• Making it more difficult to learn• Making it more difficult to use• So… Life’s simpler but more complicated!• Creeping featurism: Attractive but deadly!

Human Error?

• You use a device and continually make the same mistake… – Is it your fault?– Is it the device’s fault?– Is it the designer’s fault?

• Yes to all three… but knowing what mistakes humans are subject to make allows the designer to avoid them.

Folk Theory and Home Heating Thermostats

• Humans want causality!• Naïve theories abound.

• The timer theory: Half way is half the time.

• The valve theory: Half way is half open.

• Truth: It’s on full blast or it’s off.

Norman’s Structure of Action

• To get something done you need:– A goal to achieve in that world– A world in which to act

• Then take action:– Make a change in the world– Check the world to see if the goal has been met

Goals

• Goals are Underspecified: They don’t tell precisely what is needed to be done to accomplish them

– Get dressed– Go to work– Drive home

The Action Cycle:Two types of Actions

• Execution– Make a change in the world

• Evaluation – Check the world to see if the goal has been met

Stages of Execution

• Form the intent to act on the goal (mental)

• Form the action sequence required to achieve that goal (mental)

• Execute that action sequence (physical)

Stages of Evaluation

• Perception of the world as it is after execution

• Interpret that perception according to our expectations

• Evaluate the interpretation against our intentions and our goals

Goals

• Intentions

• Action sequence

• Execute

• Evaluate interpretations

• Interpret perceptions

• Perceive the state of the world

World

Norman’s Seven Stages of Action• Form the goal• Form the intention• Form the action sequence• Execute the action sequence• Perceive the state of the world• Interpret the perception• Evaluate the interpretation against expectations

Everyday Tasksa class of tasks we all do all

the timein the course of each day

• Humans are Opportunistic in nature– They take advantage of circumstances– Implies that action is triggered by opportunity

• Use the environment to trigger activity• Not necessarily planned in advance

– you are reminded as you walk around that…– the dishes need washing– you need to shop for groceries

Gulf of Execution

• The difference between the intentions on the part of the human and the allowable actions on the part of the system

• VCR bridges the gulf of execution found in the reel-to-reel videotape machines… there is no way to foul up the threading the machine.

Gulf of Evaluation

• A measure of the amount of effort on the part of the user needed to interpret the state of the device and determine if (or how well) expectations have been met.

• VCR: Can’t tell if a tape is in the machine. Press play and it just sits there (in some models)

Norman’sPrinciples of Good

Design• Visibility: Can the state of the machine and the possible available actions be easily determined by inspection?

• Good conceptual model: Is the system image a good one for the intended users?

• Good Mappings: Are there ties between actions and results? Controls and effects?

• Feedback: Does the user get feedback from the results of actions taken.