1. Ergonomics –The Study of Work

2. Origins in WWII As more controls and devices were added to British combat planes pilots made more errors, endangering the missions

3. Affordances

4. Ergonomics studies the range of normal Human Abilities and Limitations

5. Mappings & Affordances Mapping is the relationship between objects. Turn the steering wheel right the car goes right. Turn signals on a motorcycle: flip up, flip down – bad UI

6. Novice Users – Confused – Willing to learn – Makes errors of understanding – Blames themselves

7. Intermediate Users – Confident – Makes slips, not erros – Invokes “magical thinking” Herbert Simon – Satisficing Folk theories – eg: Turning the thermostat on high will heat the house faster – Timer theory – thermostat controls how long the device is on – Valve theory: like a hose – turn up the valve and increase the rate of heat flow The theory may be incorrect but it should be usable

8. Expert Users – Confident – Explains and understands why things work – Able to use tools in innovative ways – Tends to blame the designer

9. Types of Errors Capture Error - where one frequent behaviour replaces another (drive to work instead of a friend’s) Descriptive Error – use the wrong object which has a similar use – throw spaghetti into the garbage instead of a pot Data Driven errors – Metathesis in typing – Entering an old phone # instead of new one – Slips of the tongue

10. Types of Errors Continue Associative Activation Errors – Pick up phone and saying come in – Answering office reply at home Loss of Activation Error – Start on one activity (going to the next room) and forgetting why you went Mode errors – When different devices have different modes of operation and you use the wrong command Target errors – When you go for one control instead of the other (maybe the ejection button shouldn’t be next to the ignition)

11. The Human Eye has Rods and Cones Rods detect black and white and allow us to discern lines and edges – they are shape detectors Cones allow us to detect colour

12. Distribution and Sensitivity of Cones RedBlue Low550500450 High700580480 Peak575505 (G) 575 (Y) 470 %64%32%4%

13. Visual Acuity of the Human Eye ½’ of arc to distinguish pixels 18’ of arc to distinguish text (Assuming vision corrected to 20/20) Always check the distance from the monitor and compare to monitor specs. 1’ (one minute) of arc = 1/60 th of a degree

14. Visual Acuity A Too Small To Read This is large enough to read 18’ of arc ½’ of arc Too close – one can see individual pixels Good! Pixels blend together

15. Eye Hand Co-ordination Fitt’s Law for Reaction Time T = k 0 + k 1 log 2 (Distance/Size +.5) There is a minimum reaction time. The Further the hand has to travel the longer it takes. The Smaller the object the Longer it takes. Big objects close by are quickly and accurately clicked. Small objects far away take longer and are easily missed