Interaction Design

CMPT 363

“You only use what you understand.”
— Steve Jobs

What is the practice of strategic interaction design?

Topics to Explore

  1. 5 Dimensions of IxD
  2. HCI Laws

Interaction Design

5 Dimensions of IxD

1D: Words

Includes all text visible to the user.

2D: Visual representations

Includes typography, imagery, icons, color palette, etc.

3D: Physical objects or space

Includes computer keyboards, mice, trackpads, and touchscreens that users interact with and the space they interact within.

4D: Time

Includes all interactive elements that change over time, such as motions, sounds, and animations.

5D: Behaviour

Includes how users react to an interaction - physically and emotionally.

Interaction Design

HCI Laws

HCI Laws

  • Miller’s Law
  • Hick’s Law
  • Power Law of Practice
  • Fitts’ Law

Miller’s Law

In 1956, George Miller published the paper “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information”

Miller’s Law

More recent research (Baddeley, 1986) indicates the capacity is closer to 3-4 items

Miller’s Law

The ability of working memory to store short-term information can be increased by “chunking” data

Hick’s Law

Hick’s law estimates the time it takes for a person to make a choice as a result of the number of possible choices presented

Hick’s Law

T = b log2(n + 1)

b = empirically determined constant
n = number of choices

Power Law of Practice

Mathematically expresses that performing the same physical action over a period of time tends to increase performance

Power Law of Practice

Tn = T1 n-a + c

T1 = first time to perform task, n is number of trails
Tn = time to perform task after n times
a = .4
c = limiting constant

Fitts’ Law

Fitt’s law (1954) is a model of human movement

Fitt’s Law

T = k log2(D/S + 0.5), k ~ 100 msec.

T = Time to move the hand to target
D = distance between hand and target
S = size of target


  1. 5 Dimensions of IxD
  2. HCI Laws

References and Suggested Books

  • Design for Emotion by Trevor van Gorp and Edie Adams
  • Designing Interactions by Bill Moggridge
  • A Web for Everyone: Designing Accessible User Experiences by Sarah Horton and Whitney Quesenbery
  • Understanding WCAG 2.0,
  • Designing User Interfaces for an Aging Population by Jeff Johnson and Kate Finn
  • Emotional Design by Donald Norman

Image Credits