The Availability Heuristic

1
The Availability Heuristic

• assess the frequency of a class or the
  probability of an event by the ease with which
  instances or occurrences can be brought to mind
  (TK, 74 1127)

2
Availability heuristic

• Events that are easy to imaging
• spring to mind
• are judged to be more frequent
• I.e.., highly vivid,
• emotional
• can be imagined

3
Example Availability bias

• Which is more likely cause of death in US?
• killed by falling airplane parts?
• shark attack

4
Implications What more probable (plausible)

• Media coverage (crime rate )
• Events easy to image (terrorist attack)
• Events/outcome the are difficult to visualize
• (interaction effects)

5
Are easily imagined events judged to be more
probable?

• Carroll (1978)
• 1976 election
• Imagine Carter wins
• or
• Imagine Ford wins
• predict Who is likely to win?

6
What if event is extremely negative?

• DENIAL
• nuclear war
• AIDS
• Environmental disasters
• Global warming
• rape of Indian Ocean

7
VIVIDNESS

• how concrete or imaginable something is
• visuals
• TV
• face-to-face communications

• What course to take?
• Recommend Not
• Condition
• Face-to face 4.73 .50
• No eval-
• uation 3.33 1.39
• Base rate 4.11 .94
• (Borgida Nisbett, 1977)

8
Legal Significance? (during jury deliberations?)

• Pallid condition
• On his way out the door, Sanders (the defendant)
  staggered against a serving table, knocking a
  bowl to the floor

• Vivid version
• On his way out the door, Sanders staggered
  against a serving table, knocking a bowl of
  guacamole dip to the floor and splattering
  guacamole on the white shag carpet.

9
Why? Delayed effect

• Vivid information easier to remember
• Easier to retrieve from memory
• Vivid events may be judged more probable

10
TYPE of INFORMATION

• Most likely to be remembers
• more persuasive (delayed effect)
• Case histories (versus stat abstract)
• Video (versus written oral
• presentations)
• Personal experience
• VALID, RELIABLE, TIMELY

11
How to use these insights?

• Publicize explicit but non-obvious comparisons
• More people will die from stomach cancer than
  from car accidents