Understanding users

Objectives  Gestalt Principles of Perception  Design principles  Development activity

Core cognitive aspects  Attention  Perception and recognition  Memory  Reading, speaking and listening  Problem-solving, planning, reasoning and decision-making, learning  Most relevant to interaction design are attention, perception and recognition, and memory

Gestalt Principles of Perception  A premise of Gestalt psychology is the idea that humans strive to find the simplest solutions to incomplete visual information.

Principles  Humans organize things into meaningful units using:  Proximity: we group by distance or location  Similarity: we group by type  Symmetry: we group by meaning  Continuity: we group by flow of lines (alignment)  Closure: we perceive shapes that are not (completely) there  Also  Common fate  Surroundedness Principle  Proportion  Area Principle

Five principles User interface design and evaluation By Deborah L. Stone, Debbie Stone

Design Principles  Design Principles  Fitts’ law  80/20 Rule  Alignment  Aesthetic-Usability Effect  Flexibility-Usability Tradeoff  Elegance and simplicity Universal Principles of Design, Lidwell, W., Holden, K., Butler, J., Rockport Publishers: Massachusetts. Designing Visual Interfaces, Mullet, K. Sano, D Prentice Hall: Upper Saddle, New Jersey.

Fitts’ law  Time required to move to a target is a function of the target size and the distance to the target.  Smaller and more distant a target, longer it takes to move to the resting position over the target.  Faster movement and smaller targets, greater error rate due to the speed-accuracy tradeoff.

Tapping Experiment Longest time, most errors?

Fitts’ law  Fitt’s law only applies to rapid pointing movement  Not for more continuous movements, such as writing or drawing.

Fitts’ law  Pointing movement typically consists of:  Ballistic movement - one large quick movement toward a target,  Homing movement - followed by the adjustment movements to a resting position over (Acquiring) the target.

Fitts’ law Implications  When rapid movements are required and accuracy is important, controls are near or large.  When controls not used frequently or when they cause problems if accidently activated, more distant and smaller.

Tapping Experiment When rapid movements are required and accuracy is important. When controls not used frequently or when they cause problems if accidently activated.

Fitts’ law Implications  Use large objects for important functions (Big buttons are faster).  Use pinning actions of the sides, bottom, top, and corners of your display.

Fitts’ law Implications  Use pinning actions of the sides, bottom, top, and corners of your display.

Faster Single-row toolbar with tool icons that "bleed" into the edges of the display is faster than a double row of icons. Fitts’ law Implications Slower

Fitts’ law Implications  Things done more often -  assigned a larger button.  Things done more often -  closer to the average position of the user's cursor. Since distance between the cursor position and pop-up menu is small, menu items can be access more quickly.

Fitts’ law Implications  Buttons with text labels and icons are usually easier to use than buttons that contain only icons.  Larger size makes them an easier target to locate. SETTINGS

Fitts’ law Implications  Target position relative to the current cursor position is important: 1. Users can most easily move the mouse cursor horizontally from the current position. 2. Moving to the right is more efficient than moving to the left. 3. Next in efficiency is moving straight downwards. 4. Upward moves are slower than downward ones. 5. Diagonal moves are generally slower than horizontal or vertical ones.

Fitts’ law (example)  Technique to reduce acquisition time - Center child menu, so no item is more than total items/2 away from mouse. Source:

80/20 Rule  Approximately 80% of effects generated by any large system are caused by 20% of the variables in that system.  80 percent of a product's usage involves 20 percent of its features.  80 percent of a town's traffic is on 20 percent of its roads.  80 percent of a company's revenue comes from 20 percent of its products.  80 percent of innovation comes from 20 percent of the people.  80 percent of progress comes from 20 percent of the effort.  80 percent of errors are caused by 20 percent of the components. The first recognition of the 80/20 rule is attributed to Vilfredo Pareto, an Italian economist who observed that 20 percent of the Italian people possessed 80 percent of the wealth. The seminal work on the 80/20 rule is Quality Control Handbook by Joseph M. Juran (Ed.), McGraw-Hill, 1951.

80/20 Rule  Design and testing should focus on 20% of features used 80% of the time.  Noncritical functions part of the less-important 80% should be minimized or removed from the design.

80/20 Rule  Identify the critical 20% of the functions that are used 80% of the time and…  make them readily available to users.

Alignment  It is easier to perceive a structured layout.  Place elements so edges line up along common rows or columns.  Nothing should be placed arbitrarily.

Alignment  Every item should have a visual connection with something else on screen (Williams, R. p. 27)  Creates a sense of unity and cohesion  Contributes to the design's overall aesthetic and stability.  Alignment can help lead person through a design.

Alignment In text  Left-aligned and right-aligned text blocks  better than center-aligned text.  Left-aligned and right-aligned text blocks  presents clear, visual cue against which other elements of the design can be aligned.  Center-aligned text  has more visually ambiguous alignment cues, and can be difficult to connect with other elements.

Alignment You are looking at center alignment. By Susan Fitzgerald February 06, 2013

Alignment You are looking at center alignment. By Susan Fitzgerald February 06, 2013

Alignment You are looking at left alignment. By Susan Fitzgerald February 06, 2013

Alignment You are looking at left alignment. By Susan Fitzgerald February 06, 2013

Hello World

Hello world Navigation Section Headings Navigation SEARCH

Hello world Navigation Section Headings Navigation SEARCH

Hello world Navigation Section Headings Navigation SEARCH It is easier to perceive a structured layout.

Remember : Screen layout  Use grids for layout  Grid 960 (  The Grid System (

1.Divide screen into rows and columns 2.Identify elements that are common throughout 3.Essential and common elements are made to fit within the grid 4.Group related elements together 5.Create sample and get feedback. Gives a coherent visual structure. Reduces clutter and provides users visual cues to follow.

50 px 100X100 px

Help users understand

Alignment Source:

Alignment

alignment - text  We read from left to right (English and European)  align left hand side Willy Wonka and the Chocolate Factory Winston Churchill - A Biography Wizard of Oz Xena - Warrior Princess May be boring but its readable! Willy Wonka and the Chocolate Factory Winston Churchill - A Biography Wizard of Oz Xena - Warrior Princess

Alignment - names  Scanning for surnames  make it easy! Alan Dix Janet Finlay Gregory Abowd Russell Beale  Dix, Alan Finlay, Janet Abowd, Gregory Beale, Russell Alan Dix Janet Finlay Gregory Abowd Russell Beale

Alignment - numbers Think purpose! Which is biggest?