HCI

1
HCI

• Locus of Attention

2
Consciousness

• You cannot deliberately make conscious thoughts
  unconscious
• Locus place/site
• Different from focus implies volition

3
An Elephant

• Dont think about an elephant
• Cant do it, eh?

4
Perceptions

• Perceptions decay over time
• Implication cant assume users will remember
  essential details

5
Automaticity

• Habitual responses common in habitual tasks
• A set of actions to accomplish a task become
  grouped into a single action
• How can we combat this?

6
Confirmation Box

• The action you are about to take is irrevocable.
  It will cause permanent loss of the file. If
  this is your intention, type backward the twelfth
  word in this box.
• Why does this work?

7
Absorption

• The more intense the focus
• The more difficult the transition of locus of
  attention
• The more stimulus needed to change locus of
  attention
• Message most likely missed when its most
  important for it not to be missed

8
Implications of Locus of Attention

• Fixed attention (magicians)
• Recency of work/files
• Windowing (layered windows in GUI)
• Web sites (returning from whence you came)

9
Fitts Law (Movement)

• Time (msec) a b log2(D / S 1)
• Given the size of target (S) - 1 Dimension
• Given distance to be moved (D)
• a b are constant fudge factors (50,150)

S
Initial CursorPosition
D
Target
10
Hicks Law (Selection)

• Time (msec) a b log2(n1)
• Given a number of options/choices (n)
• a initial focus cost
• b per-group focus cost
• Habituation effects b
• Organization effects a b
• Selecting an item of one set is faster than
  selecting via hierarchical groups