University of Connecticut MECHANICAL ENGINEERING

“The design of everyday things”“The design of future things”

D. Norman

Design for the human factor

University of Connecticut MECHANICAL ENGINEERING

The design of everyday things

The designer has to couple psychology of people to the knowledge of how things workExample: pitcher with handle and spout on same side

Design for the human factor

University of Connecticut MECHANICAL ENGINEERING

Fundamental Principles of Designing for People

Provide good conceptual models

Make things visible

Make invisible things visible

University of Connecticut MECHANICAL ENGINEERING

Provide Good Conceptual Models

• Mental model of the way objects work, events take place, or people behave

• Results from tendency to form an explanation of how things work

• Mental models are often constructed from fragmentary evidence

• Some faulty models lead to frustration in everyday life

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Provide Good Conceptual Models

• Examples- Room thermostat: in cold room, if in a hurry to get room warm

quickly, will not heat up faster if you turn up thermostat to maximum.- Temperature control on a refrigerator & freezer

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Conceptual Models of Refrigerator Controls

Model A: Image gained from controls and instructions

University of Connecticut MECHANICAL ENGINEERING

Conceptual Models of Refrigerator Controls

Model A: Image gained from controlsand instructions

Model B: Correct conceptual model

Problem: Which compartment has the thermostat and where are the controllers?

University of Connecticut MECHANICAL ENGINEERING

Make Things Visible - I

Things work from their visible structureaffordances ("is for")

a chair affords ("is for") support and therefore affords sitting

affordances give clue to operation of things plates >> for pushing, knobs >> for turning, slots >>for inserting things

when designers take advantage of affordances, no picture, label instruction is required.

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Make Things Visible - II

Mappings: relation between 2 things, i.e. controls & their movementssteering wheel and directionmeasurable parameters like amount and loudness less clear for pitch, taste, color (no characteristic plausible

relation)

A bad mapping design (vertical set of switches: which switch controls which source)similar to many airplane cockpits where many switches are

close and look/feel the same

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How to Make Things Visible - III

bolt click when closing door bolt

door lock click when locked by fob

"zzz" sound of zipper when working

click of toaster when bread pops up

whistle on tea pot

Window versus UNIX

MS Word versus LaTex: WYSWYG\frac{T_2}{T_e} = \left( \frac{p_e}{p_a} \right)^{-\frac{\gamma-1}{\gamma}}.

versus

1

2 e

e a

pT

T p

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Some things require action with no clue of result

Example 1: digital watch with several push buttons the more functions included, the more questions on

operation

Example 2: kitchen stove top with controlsarbitrary arrangement

natural mappings

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Arbitrary Arrangement

Natural Mappings

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Some things require action with no clue of result

Example 3: water faucet designcontrols: temperature, volume3 problems

(2) relate to mapping of intentions to actions– Which is hot / cold?– What increases / decreases (action) water flow?

(1) relates to problem of evaluation– How to determine if volume / temperature is

correct?

University of Connecticut MECHANICAL ENGINEERING

Some things require action with no clue of result

Example 3: water faucet design [cont’d]mapping

convention is hot on left, screw clockwise to tighten / shut off water– What if a lever is used [Moen design]?

are conventions universal?– vertical faucet arrays on wall?– Europe does not have the same conventions

asymmetricaly placed faucets for esthetics 2 separate spigots evaluation is normally determined by direct feedback, i.e. trial and

error

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The Designer Challenge

Natural evolution of a design is normally used, but time factors frequently preclude thisDesigners are not typical users

Designers clients are frequently not users

Designing for special people requirements left-handedness size / height of user age / infirmity of the user

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Design for Zero Errors

Design for avoiding misinterpretation, e.g. operators at 3-mile island plant made numerous errors and misdiagnoses, but each one was logical and understandable at the time

Examples: Adaptive cruise controlKorean Air Lines KAL007

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Design for Zero Errors

Example: Adaptive automotive cruise controlsystem designed to sense proximity to cars in front and

automatically slow down car.System designed to sense no upstream cars and

accelerate car to set speedConsider the following scenario

Car driving with cruise control at set speed, say 65 mph. Car runs into traffic and decelerates to 20 mph. After a period of time, car makes right turn to exit highway. System senses no traffic and accelerates vehicle to 65 mph.

What is the problem, if any?

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Design for Zero Errors

Example: Korean Air Lines KAL007 shot down over Russia in 1983 after crew mis-programmed the flight path into the inertial navigation system (INS)system could not be reprogrammed in flight [before GPS],

needed to return to original airport to be reset.3 previous KAL planes had done this over the last 6 monthsKAL pilots warned next plane to return to base would be

punished (social constraint) real error is a design that can easily be set to the wrong settingsU.S had been flying reconnaissance flights near Soviet bases

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What should designers do?

Understand the causes of error and design to minimize these causes

Make it possible to reverse actions (undo them) or make it harder to cause basic error

Make it easier to discover errors

Change the attitude towards errors. Don't think of the user making errors, think of the action as an approximation of what is desiredExample 1: locking keys in a carExample 2: leaving the light on in a car