SOME COGNITIVE FALLACIES AND BIASES
Anchoring: The tendency for first impressions, even irrelevant ones, to continue to influence
decision-making. A startling example: students were asked to estimate the number of nations in
Africa. Before they estimated it, a wheel with the numbers 1-100 on it was spun to generate a
random number. Those for whom the wheel came up 12 consistently estimated lower than those
for whom the wheel came up 92, even though there is obviously no relation between the random
number from the wheel and the actual number of African nations.
Availability Bias: Our tendency to base evaluations of probability on the ease with which
examples are recalled. However, ease of recall can result from reasons that have nothing to do
with actual frequency. Shark attacks and airplane crashes are easy to recall because of their
emotional salience; as a result we tend to greatly overestimate their frequency. A special case of
this is the so-called “flashbulb memory”, a memory concerning where we were or what we were
doing when some especially noteworthy or emotionally charged event happened. Experimental
studies reveal that these flashbulb memories, in which we are supremely confident, are in fact no
more likely to be true than other memories.
Barnum Effect: Named for famed circus administrator P. T. Barnum, this names our tendency
to believe that descriptions of us are accurate so long as we think that those descriptions were
intended to be about us. More generally, it involves interpreting ambiguous data in ways that
make it seem accurate. For example, people given the exact same personality description all rate
it is being an accurate description of themselves when led to believe that it was generated
specifically for them.
Base Rate Neglect: When making judgments about probabilities, we often ignore base rates in
favor of good stories. Base rate data tells us how representative one feature is of a whole
population, or how likely an event is to occur independently of specific conditions. For example,
from the fact that most men that have committed sexual assault have used pornography, we often
conclude that pornography causes sexual assault. The missing base rate data is what percentage
of men, independently of whether they have committed sexual assault, has used pornography.
Clustering Illusion: The false appearance of streaks in random distributions of data. For
example, the coin flip sequence HTHTHTTTTHTT appears to be non-random because of the
appearance of a large streak of mostly tails.
Confirmation Bias: Our tendency to seek out and more effectively recall evidence that confirms
a hypothesis rather than evidence that disconfirms it. Also refers to our tendency to interpret
ambiguous evidence in a way that supports rather than refutes the hypothesis in question. Related
to this is our tendency to evaluate evidence supportive of our beliefs less critically than those that
potentially refute our beliefs, and to be more likely to remember confirming evidence.
Conjunction Effect: When given two statements, A and B, we often judge A and B together to
be more likely than A or B alone. This is generally true when A and B seem to “fit” well. For
example, we tend to judge that the claim “Jennifer is a feminist philosopher” to be more likely
than either “Jennifer is a feminist” or “Jennifer is a philosopher” because being a philosopher
seems to “fit” with being a feminist. In actuality, the likelihood of any two claims both being true
is less than the likelihood that either alone is true.
Discounting the Future: Our tendency to overweigh the impact of immediate and short-term
gains and losses compared to long-term ones.
Endowment Effect: Our tendency to rate the value of something we already own above the value
of something we do not possess. For example, we routinely set a price to sell something we own
significantly higher than we indicate we would be willing to pay to attain that same object.
False Consensus Effect: Our tendency to overestimate the degree to which others are similar to
us in their beliefs, experiences, values or characteristics.
Focused v. Unfocused Predictions: We tend to remember unfocused predictions (vagaries such
as “you will meet a tall, dark stranger”) that are confirmed, and forget those that are
disconfirmed. This is because only confirmation is memorable. (Thus, this is related to both the
confirmation and availability biases.) We also tend to interpret ambiguous results in ways that
confirm unfocused predictions.
Framing Effect: The decisions we make often depend not on the information available to us, but
rather on the way in which the decision is given to us. For example, people tend to reject medical
procedures that have a 10% fatality rate, but accept medical procedures that have a 90% survival
rate. 10% fatality just is 90% survival; the difference in acceptance is a result of the way in
which the decision is presented to us, or framed. The context of the decision influences the
decisions themselves.
Fundamental Attribution Error: This is the attribution of situational behavior to character
traits (typically made of others), such as judging that the person in line in front of us who is short
with the cashier is just “a jerk”. Social psychology research has indicated that situational factors
are far better predictors of behavior than character traits; yet we routinely explain behavior by
appeal to such traits and ignore situational factors.
Hindsight Bias: Using data currently at our disposal, we tend to greatly exaggerate the degree to
which events that have already happened were predictable based on the evidence available at the
time. In general, events that have actually happened are routinely judged to have been likely, and
events that failed to occur to have been highly unlikely, regardless of their actual probability.
Honoring Sunk Costs: We honor sunk costs any time we follow a course of action we no longer
desire to follow or that is not working because we have already invested in it. As a result, we end
up paying (with time, money or both) to do what we don’t want to do.
In-Group Favoritism: Our tendency to empathize with (and hence consider the interests of)
others based on the degree to which they are similar to us, and hence familiar. This is
independent of considerations of bias in the pejorative sense.
Lake Wobegon Effect: Named after the fictional town where “every child is above average”,
this names our tendency to overrate our abilities compared to others. For example, most people
rate themselves as above average in intelligence, leadership ability, studiousness, job
performance, and driving ability; while almost no one rates themselves as below average in these
things.
Omission Bias: This is the intuitive assumption that doing harm is worse than failing to prevent
harm. The problem is that this intuition takes no account of the degree of harm that actually
occurs.
Outcome Bias: Our tendency to judge behavior more positively or negatively based on what we
know (or believe) about the outcome of that behavior. For example, many more people opposed
the 2003 war in Iraq after the war began to stagnate than before, despite the fact that the same
evidence was appealed to (misinformation about Iraq’s possession of WMDs, concerns about
lacking an exit strategy, concerns about whether Iraq was connected to the 9/11 terrorist attacks,
etc.). Related to Hindsight Bias.
Outrage Heuristic: Our tendency to evaluate the moral status of actions or circumstances based
not on actual considerations of harm, but on how angry it makes us or how offended by it we
happen to be.
Overclaiming: Our tendency to overestimate the value and impact of our own contribution due
to our greater awareness of it. This can often lead us to self-serving and profoundly unjust
accounts of what is fair and/or deserved.
Overconfidence: Our tendency to overestimate the reliability and accuracy of our own beliefs.
Representativeness Bias: We often estimate likelihoods and make judgments based on
conformity to a stereotype. For example, we will tend to judge it to be far more likely for a
woman to be a lawyer than a waitress if we know that she reads a lot and majored in philosophy.
The problem is that any woman is more likely to be a waitress than a lawyer—our decision is the
result of the fact that reading a lot and majoring in philosophy fit our stereotype of lawyers better
than our stereotype of waitresses. There is experimental evidence that indicates that many of
these stereotypes (or prototypes) are automatic; that is, they influence our decision without
conscious awareness.
Source Amnesia: Our tendency to recall information better than the source of the information.
Status Quo Bias: Our tendency to overestimate the value or effectiveness of existing options,
policies, etc.; including our tendency to both underemphasize both the losses that come from
maintaining the status quo as well as the potential gains of change. This often persists even in the
face of a clearly superior alternative.
Subset Fallacy: Our tendency to reject policies that help some because one particular group is
not benefited by it.