that describes the common human tendency
to rely too heavily, or "anchor," on one trait or piece of information when making
During normal decision making, individuals anchor, or overly rely, on specific
information or a specific value and then adjust to that value to account for other elements
of the circumstance. Usually once the anchor is set, there is a bias toward that value.
Take, for example, a person looking to buy a used car. They may focus excessively on
the odometer reading and model year of the car, and use those criteria as a basis for
evaluating the value of the car, rather than considering how well the engine or the
transmission is maintained.
rule of thumb
, where people
base their prediction of the frequency of an event or the proportion within a population
based on how easily an example can be brought to mind. In these instances the ease of
imagining an example or the vividness and emotional impact of that example becomes
more credible than actual statistical probability. Because an example is easily brought to
mind or mentally "available", the single example is considered as representative of the
whole rather than as just a single example in a range of data. Several examples:
Someone argues that cigarette smoking is not unhealthy because his grandfather
smoked three packs of cigarettes a day and lived to be 100. The grandfather's
health could simply be an unusual case that does not speak to the health of
smokers in general.
The president gives the State of the Union address and says that walnut farmers
need a special farm subsidy. He points to a farmer in the balcony who is sitting
next to his wife and explains how the farmer will benefit. Others who watch and
discuss later agree that the subsidy is needed based on the benefit to that farmer.
The farmer, however, might be the only person who will benefit from the subsidy.
We don't know if walnut farmers in general need this subsidy.
The following example is due to the psychologist
: "'Are there
more words with "r" as the first letter than with "r" in the third position?' 'Are
there more words beginning with "k" than with "k" as the third letter?' Unless you
sense that there is some sort of trick being played, you are likely to answer yes to
both questions. But you would be wrong - there are more words with 'r' or 'k' in
the third position than there are words beginning with each letter. The mistake is
made because words, both in dictionaries and in our minds, are arranged by their
initial letter. It is easy to retrieve from memory words beginning with 'r', like
'roar', 'rusty' and 'ribald', but much more difficult to recover words like 'street',
'care' and 'borrow', despite their greater frequency."