Lecture 15. Interaction paradigms-2. CENG 412-Human Factors in Engineering July

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1 Lecture 15. Interaction paradigms-2 CENG 412-Human Factors in Engineering July

2 Announcements Final project presentations start on July 20 Guidelines will by posted by July 13 Assignment 2 posted Due: July 20 by the start of the class (both paper copy and ) New office hours: Monday, Thursday 10:00 am-11:00 am Otherwise by appointment 2

3 Outline Direct manipulation wrap-up Norman s model of human-system interaction Gulf of execution Gulf of evaluation Principles of display design Reading: - Don Norman The design of everyday things: - Ch.1 (pdf on course site) - Ch 2 (hard copy) 3

4 Direct manipulation cues Affordances Constraints Natural mapping Visibility Feedback 4

5 Feedback Feedback is sending back to the user information about what action has been performed, or is in process. Visibility of the effects of the operation tell you if your action worked correctly Systems should be designed to provide adequate feedback to the users to ensure they know what to do next in their tasks 5

6 Visual feedback: WYSIWIG The term describes a user interface (most often a text editor) that allows the user to view on screen how a document will look when it is printed to paper or displayed in a Web browser. The most interesting feature: on-line visual feedback which creates the feeling of ease-of-use MS Word versus LaTeX 6

7 Feedback: the progress indicator bar 7

8 Exercise (sample question midterm 2) Consider the window-resizing interface in Windows Discuss the design quality of this interface with respect to the following concepts: affordance mapping feedback 8

9 Metaphors useful when you want to borrow a conceptual model from a real object that the user already knows Conceptual model=how the object works Metaphors use the power of positive transfer 9

10 Metaphor: example #1 The Macintosh trashcan: good metaphor for deleting files and documents Stretching the trashcan metaphor to include the function of ejecting diskettes: Drag an image of the diskette to the trashcan to eject it from the computer Good idea or bad? "I don't want to delete the files on the diskette, I just want the computer to spit it out." 10

11 Lessons learned Metaphor selection: one of the first and most important tasks in interface design. But Good user interface design is not only based on metaphors Metaphors constrain the conceptual model of the interaction. Magical extensions of metaphors (ex. Trashcan) are mostly perceived as counterintuitive. Metaphors can constrain your design 11

12 Metaphors and icon design Exercise: write down the function of each of these icons. Hint: all icons belong to an word processor toolbar 12

13 Make icons comprehensible Please read the following text What is the main difference between the icons shown here and the icons shown on the previous slide? 13

14 Solution: attach actions to objects 14

15 Donald Norman s model: the executionevaluation cycle Seven stages user establishes the goal formulates intention specifies actions at interface executes action perceives system state interprets system state evaluates system state with respect to goal Norman s model concentrates on user s view of the interface 15

16 execution/evaluation loop execution goal system user establishes the goal formulates intention specifies actions at interface executes action perceives system state interprets system state evaluates system state with respect to goal evaluation 16

17 execution/evaluation loop execution goal system user establishes the goal formulates intention specifies actions at interface executes action perceives system state interprets system state evaluates system state with respect to goal evaluation 17

18 execution/evaluation loop execution goal system user establishes the goal formulates intention specifies actions at interface executes action perceives system state interprets system state evaluates system state with respect to goal evaluation 18

19 execution/evaluation loop execution goal system user establishes the goal formulates intention specifies actions at interface executes action perceives system state interprets system state evaluates system state with respect to goal evaluation 19

20 Using Norman s model Some systems are harder to use than others Gulf of Execution user s formulation of actions actions allowed by the system Gulf of Evaluation can the user understand the feedback given by the system? can feedback be interpreted in terms of intentions and expectations? 20

21 Gulf of execution Gap between the mental model (task language) of the user s goals and the system language Ex: if a person wants to record a movie currently being shown on her VCR: In user language "Hit the record button" In system language 1) Hit the record button. 2) Specify time of recording via the controls X, Y, and Z. 3) Select channel via the channel-up-down control. 4) Press the OK button. 21

22 Gulf of evaluation In the VCR example, when recording, the 'record' control should signal that it is activated. 22

23 Human error - slips and mistakes slip understand system and specify a valid goal correct formulation of action incorrect action mistake may not even have right goal! Wrong mental model of the system Fixing things? slip better interface design mistake better understanding of system 23

24 Human errors (cont d) Example of slips: - intended action is replaced by another action with many features in common - pouring orange juice into your cereal Lesson for interface design: avoid actions with very similar descriptions: long rows with identical switches, adjacent menu items that look similar 24

25 Human errors (cont d) Mistakes occur due to wrong conceptual model Sometimes harmless: electricity as water Plugging in a power cable is like plugging in a water hose, with electrons travelling up through the cable into the appliance Even if wrong, user model is simple and the interface supports it Sometimes misleading: thermostat as a valve Consider a household thermostat controlling the temperature of the room. User s goal: heat up the room to the desired temperature as fast as possible Two possible actions: turn up the thermostat to maximum temperature; turn up the thermostat to the desired temperature If conceptual model for thermostat is a valve, then the user will turn up the thermostat to the maximum temperature. WRONG! A higher thermostat setting will not make the room warm-up faster If conceptual model is on-off switch at a set temperature, user will turn up thermostat to the desired temperature. 25

26 Exercise (sample question midterm 2) Read carefully the text below. What gulf makes the goal of timing events hard to reach for our user? I am training hard for my first marathon and I'd like to check if my times are getting faster. My digital watch claims that it can record the last 60 timed events. The watch has more computing power than the original Apollo mission, so recording 60 numbers should be trivial--yet after 30 minutes spent over the user manual I was still baffled. Instead I used the blank back page of the manual to write down today's time and gave up on finding out about my previous runs. Something tells me that the designers of this watch do very little running themselves. 26

27 Interaction paradigms applied to the design of displays and controls 27

28 What is a display? A human-made artifact designed to: Facilitate perception of information Facilitate integration of information for the completion of a certain task Facilitate further processing of information Give appropriate feedback to user s actions Acts as a medium between the information generated by the system and the user s mental model of the process. 28

Types of Displays A display does not have to be associated

road signs Displays may be visual, auditory, haptic (touch),

29 Types of Displays A display does not have to be associated with a computer (example: speedometer on car, knob on gas stove position shows current setting). A display can be static: e.g. road signs Displays may be visual, auditory, haptic (touch), etc. Examples: Visual: Flashing light on ambulance, Auditory: siren on ambulance, Haptic: cell phone in vibrate mode 29

30 Static versus dynamic displays 30

31 A classification of displays Along three dimensions: Physical properties (physical implementation of the display) Color or monochrome; visual or auditory modality etc. Task that the display is intended to support information visualization search, query process control, decision-making learning Characteristics of the human user that dictate the best mapping between display and task Guidelines for display design can be structured along these 3 dimensions as well. 31

The Interaction. Using Norman s model. Donald Norman s model of interaction. Human error - slips and mistakes. Seven stages

The Interaction. Using Norman s model. Donald Norman s model of interaction. Human error - slips and mistakes. Seven stages The Interaction Interaction models Ergonomics Interaction styles Donald Norman s model of interaction Seven stages execution user establishes the goal formulates intention specifies actions at interface