v The core idea of the heuristics and biases program is that judgment under uncertainty is often
based on a limited number of simplifying heuristics rather than more formal and extensive algorithmic processing.
These heuristics typically yield accurate judgments but can give rise to systematic error. Kahneman and Tversky originally
identified three such general purpose heuristics - availability, representativeness, and anchoring and adjustment.
p.5 The impact of any idea is a product of the quality of the idea itself and the intellectual zeitgeist
[JLJ - The word zeitgeist describes the intellectual, cultural, ethical and political climate of an era or also a
trend] at the time it was offered. Successful ideas must not only be good, but timely - even lucky.
p.22-23 Modern research on categorization of objects and events... has shown that information is
commonly stored and processed in relation to mental models, such as prototypes and schemata. It is therefore natural
and economical for the probability of an event to be evaluated by the degree to which that event is representative of an appropriate
mental model... Representativeness is an assessment of the degree of correspondence between... an instance
and a category... When the model and the outcome are described in the same terms, representativeness is reducible
to similarity... an outcome is representative of a model if the salient features match or if the model has a propensity to
produce the outcome... an attribute is representative of a class if it is very diagnostic
p.560-561 bounded rationality suggests designing models specifically to reflect the peculiar properties
and limits of the mind and the environment. The decision maker is bounded in time, knowledge, and computational power. In
addition, each environment has a variety of irregular informational structures, such as departures from normality... Simon's
view of bounded rationality is that of satisficing... Satisficing asserts that our minds have evolved
all sorts of nimble tricks to perform well in the quirky structures of the real world.
The types of models developed by the satisficing view are thus fairly simple
p.581 The success of fast and frugal heuristics emphasizes the importance of studying the structure
of the information in the environment... Fast and frugal heuristics can be ecologically rational in the sense that
they exploit specific and possibly recurrent characteristics of the environment's structure (Tooby &
Cosmides, in press). Models of reasonable judgment should look outside of the mind to its environment. And
models of reasonableness do not have to forsake accuracy for simplicity - the mind can have it both ways.
p.618 The representativeness heuristic consists of the reflexive tendency to assess the
"fit" or similarity of objects and events along salient dimensions and to organize them on the basis of one overarching rule:
"Like goes with like." The heuristic reflects the belief that a member of a given category ought to resemble the cause
that produced it. Thus, the representativeness heuristic is often used to assess whether a given instance belongs
to a particular category... Still, the representativeness heuristic is only that - a heuristic. Judgments
based on representativeness should therefore be viewed with caution.
p.724 Perhaps more importantly, when properly derived, the mathematical features of actuarial methods [JLJ
from p.716, In the clinical method the decision maker combines or processes information in his or her head. In the actuarial
or statistical method the human judge is eliminated and conclusions rest solely on empirically established relations between
data and the condition or event of interest] ensure that variables contribute to conclusions based on their actual predictive
power and relation to the criterion of interest. For example, decision rules based on multiple regression techniques include
only the predictive variables and eliminate the nonpredictive ones, and they weight variables in accordance with their independent
contribution to accurate conclusions.
p.728 The research reviewed in this article indicates that a properly developed and applied actuarial
method is likely to help in diagnosing and predicting human behavior as well or better than the clinical method even when
the clinical judge has access to equal or greater amounts of information... Although theory and research suggest
that the choice of predictive variables is often more important than their weighting, statistical techniques can be used to
yield weights that optimize a procedure's accuracy when it is applied to new cases drawn from the same population. Moreover,
accuracy can be easily monitored as predictions are made, and methods modified or improved to meet changes in settings and
populations. Finally, efforts can be made to test whether new variables enhance accuracy.
