Preece et al, Chapter 3, 4, 5 Shneiderman, Chapter 5, 8

© University of Stirling 2011 ITNP43 Interface Design & The World-Wide-Web 1

Preece et al, Chapter 3, 4, 5 Shneiderman, Chapter 5, 8


Human Factors

In order to design, it is important to understand the capabilities and limitations of those we are designing for. Key point from this lecture:

–  Users share common capabilities, but are individuals with differences which should not be ignored.

Handy slogan:

–  Design for the majority, design for the minority


Physiology Particular HCI factors to consider:

–  Left or right-handed? –  Reaction times –  Movement –  Loss of usual facilities - disabilities


Reaction Times

Human reaction times: –  Audio signal - 140-160ms –  Visual signal - 180-200ms –  Pain - 400-500ms

Examples of use:

–  Design of video games –  Double-click feature on mice


Movement

Speed of movement is important for interactive systems. Examples:

–  Mouse - keyboard movement (affects choice of which controls operate which actions of the system)

–  Time taken to move to a target on screen –  Careful arrangement of menu items so that frequent

choices are placed first (and close?)


Pointing: Mice and Trackballs


Pointing: Fingers and pens Touch screen technology

possibly with a light pen. •  Pen has light-sensitive tip, is held up to the computer to

operate, and the pen detects burst of light from the screen Advantages of pen:

–  More accurate than touchscreens. –  A very direct method of drawing on the screen –  Can point directly at the screen more easily

Disadvantages:

–  Holding up pen more tiring than desk-based devices. –  Fingers are always available!


More Pointing Devices Joysticks/controllers

–  movement based, or position based –  1-d, 2-d or 3-d devices available

Micropoint –  (as in laptops)

Digital pen and tablet –  e.g. for handwriting recognition devices, such as Grafitti

on the Palm Pilot. Gyromouse

–  pick it up and it tracks your hand movement (3d mouse) Motion sensing

–  e.g. Wii, Kinect


Assistive Devices Eye movement tracking devices (slow blink to click!), Mice operated by other parts of the body (head, feet, finger, …), again useful for the disabled, or for avoiding (eg) carpal tunnel syndrome

Keyboards

Wide range of keyboards available: –  QWERTY keyboard – the “normal” keyboard –  Ergonomic keyboard –  DVORAK keyboard – keys arranged in a different order –  electronic keyboards (Swype technology)


Simpler keyboards: –  Chord keyboard – small number of

keys, used in combination –   At the limit, input may be by a

simple switch – backed up by software

Cognition

Involves understanding, remembering, reasoning, attending, awareness, acquiring skills, creating new ideas. The HCI objective is to understand the interaction between humans and computers in terms of how knowledge is transmitted between the two. Faulkner, Chapts 2 & 3



Attention Interface designers need to focus attention on the right place:

–  Structured information –  Information grouped into meaningful parts –  Amount of information presented not too much/little


Memory Different forms of human memory:

–  Short-term memory (working memory) –  Permanent long-term memory

Short-term memory is limited

–  e.g. approx 5-7 new things can be remembered for about 20 seconds in short-term memory

Chunking –  051594737 versus 051 – 594 – 737 –  GGNNTIHIAU versus HUNGATING –  GISWWYY versus ??? –  RICE?


Memory Features appropriate to memory constraints:

–  Use of graphical interfaces substantially reduces memory needed

Material is far more easily recognized than recalled

Be consistent with the user’s mental model - use meaningful interfaces:

–  command names and icons should be selected carefully

What is meaningfulness? –  Context in which used –  Task for which it is being used –  Form of the representation (icon?) –  Underlying concept being represented


Example 1: Icons (bad)

Zoc (a communications application): –  Send –  Send without carriage returns –  Send with quotes


Example 2: Easy CD Writer (bad)


Example 3: Image Preview (good)


Perception Input from the different senses

–  Auditory Perception –  Haptic (Touch) Perception –  Visual Perception

We need to understand how the input information is perceived by humans, and what difference this makes to us when considering good HCI.


Auditory Perception Uses of non-speech sounds include the following:

–  Attracting attention e.g. to an emergency situation that the user should respond to

–  Status information e.g. quiet background noise can monitor the progression of a file downloading

–  Confirmation sound associated with an action, e.g. button press, file deletion, sent message


Haptic Perception As far as use in computing design goes... Touch is an important source of feedback when using devices:

–  Pressing buttons –  Using a keyboard (raised dots on the ‘f’ and ‘j’ keys) –  Hand-held devices (e.g. phones) –  Specialist devices

For users with other senses impaired, touch may be a vital additional source of information (e.g. braille)


Visual Perception Three main aspects:

–  Size/depth –  Brightness –  Colour


Perception of Size/Depth

Our two eyes give us 3D vision, but we can see in 3D even with one eye closed.

–  In order for us to perceive the 3D world, our brains have substantial built-in ways of interpreting 2D images as 3D.

–  Designers commonly make use of these. Example...


Example: 3-D Effects for Highlighting


Perception of Size/Depth

These same automatic interpretations are responsible for many illusions.

–  Illusions are very good for revealing the interpretations we place on visual information.

– If you are interested in optical illusions visit ( the last is all one URL)

www.youramazingbrain.org/supersenses/ www.eyetricks.com psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/index.html


Size/Depth Perception

Big monster chasing a little monster?


End of Lecture

Preece et al, Chapter 3, 4, 5 Shneiderman, Chapter 5, 8

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