Chapter 12 - Judgment: Drawing Conclusions from Evidence
Induction - process in which you try to go beyond the available information- drawing inferences about a pattern, based on few
examples, or what you‟ve seen so far.
If induction is done properly, the situation is likely to occur. Therefore we compare a descriptive account of human induction (telling
us how the process usually proceeds), with a normative account (how things ought to proceed). With this we‟ll figure out if our day-
to-day judgments are sensible and justified, or just stupid.
Any factor that influences memory will influence the pattern of our conclusions and the quality of our judgments. Drawing
conclusions from past observations and memories is also referred to as learning. If memories are selective, incomplete or distorted the
conclusions we make can be questionable- can we really rely on experience?
Attribute substitution: you use this strategy when you‟re trying to evaluate some point but don‟t have easy access to the target
information. Instead you rely on another aspect of experience that‟s more accessible and (you hope) is a plausible substitute for the
info you seek.
With this you‟re relying on availability. Tversky and Kahnerman (1973) refer to this substation as the availability heuristic.
Heuristics are defined as reasonable strategies that usually lead to the correct answers. They allow for errors but are efficient.
People regularly overestimate the frequency of events that are actually quite rare because unusual events are likely to catch our
attention. You will then think of them more and they‟ll more readily come to memory. E.g., death by crime/illness.
Representative heuristic: using resemblance in place of information about category membership. I.e. you‟re trying to figure out if
David is lying, so you remember everything you can about David, and everything you know about liars, and see if he fits into the „liar‟
Reasoning from population to an instance:
Coin toss example: People believe that if heads was landed 7 times in a row it is more likely that tails will come up because it is
“overdue.” Realistically, this logic is wrong because it is a 50% chance either way. This is known as the gamblers fallacy.
Reasoning From a Single Case to the Entire Population:
If people believe categories are homogeneous, then they will expect each subset of the category, and each individual within the
category, to have the properties of that category overall and vice versa. This is the representative heuristic, similar to stereotype.
Anchoring: tendency to use the first-available estimate for some fact as a reference point for that fact, and then perhaps to make some
small adjustments from the reference point in determining out final estimate. As a result of anchoring, the first available estimate often
has a powerful influence on us, even if that estimate comes from a source with little credibility.
In many situations, we don‟t have the answer to a particular question, but we do have a “ballpark” idea of what the answer is. We then
use that initial ballpark idea as an anchor. Then make suitable adjustment to that anchor.
Covariation, much similar to correlation is a relationship between two variables such that the presence (or magnitude) of one variable
can be predicted from presence (or magnitude) of the other. Though there are many illusions on covariation (we believe things are
related, when they really aren‟t at all). A well-known example of this is the Rorschach Ink Blot Test. Even when random pictures were
paired with random meanin