Massive thank you to Michael Shermer's The Believing Brain for the brilliant definitions and many of the examples found below.
Our brains have evolved in such a way that there are a number of built-in cognitive biases that convince us that the actions we have taken in the past were the best choice at the time. These biases fall under the umbrella of belief confirmation - our minds "shape how we interpret information that comes through our senses and mold it to fit the way we want the world to be and not necessarily how it really is." And who doesn't want to always be right?
Our brains have evolved in such a way that there are a number of built-in cognitive biases that convince us that the actions we have taken in the past were the best choice at the time. These biases fall under the umbrella of belief confirmation - our minds "shape how we interpret information that comes through our senses and mold it to fit the way we want the world to be and not necessarily how it really is." And who doesn't want to always be right?
Let's outline a few of the biggest biases that alter our reality on a daily basis (these pesky guys sneak into our actions every day, though we almost never catch them.):
Confirmation Bias: the tendency to seek and find confirmatory evidence in support of already existing beliefs and ignore or reinterpret disconfirming evidence. In Biblical words, seek and you shall find.
Example: you know that a patient is checked into a psychiatric hospital and thus you interpret her copious note-taking as manifestations of a compulsive mental disorder.
Hindsight Bias: the tendency to reconstruct the past to fit with present knowledge.
Example: "NASA engineers should have known that the O-ring on the space shuttle Challenger's solid rocket booster joints would fail in freezing temperatures leading to a massive explosion."
Self-Justification Bias: the tendency to rationalize decisions after the fact to convince ourselves that what we did was the best thing we could have done. As I like to say, we can justify anything.
Example: "I couldn't have been wrong because I'm a good guy."
Attribution Bias: the tendency to attribute different causes for our own beliefs and actions than that of others.
Example: I worked hard to get where I am today, but "her success is a result of luck," or "he is successful because of circumstance and family connections."
Also, we tend to consider our own beliefs as being rationally motivated and intellectually derived, while the beliefs of others as being emotionally driven. "I am for gun control because statistics show that crime decreases when gun ownership decreases. But he is for gun control because he is a bleeding-heart liberal who needs to identify with the victim." Self-serving bias.
Sunk-Cost Bias: the tendency to believe in somethign because of the cost sunk into that belief.
Example: we hang on to losing stocks, unprofitable investments, failing businesses, and unsuccessful relationships due to the amount of money/energy we've already invested. Or as George W. Bush said, "I'm not going to allow the sacrifice of 2,527 troops who have died in Iraq to be in vain by pulling our before the job is done."
Status Quo Bias: the tendency to opt for whatever it is we are used to, that is, the status quo.
Example: The default position for "organ donor" on a driver's license is "not an organ donor", and since this seems to be the status quo, you elect to keep the default.
Endowment Effect: the tendency to value what we own more than what we do not own.
Example: You estimate the price of a mug you own at $5.25, while most everyone else values it at $2.75.
Framing Effects: the tendency to draw different conclusions based on how data are presented.
Example: A discount of $5.00 off the $50 sticker price of your widget resulted in a 2% conversion rate on your website. When the discount is framed as 10% off the $50 sticker price (still the same $5.00 discount), the conversion rate goes up to 5%.
Anchoring Bias: the tendency to rely too heavily on a past reference or on one piece of information when making decisions.
Example: "People were asked to give their last four digits of their Social Security numbers and then asked to estimate the number of physicians in New York City. Bizarrely, people with higher Social Security numbers tended to give higher estimates."
Dirty advice: when leading off in a negotiation, start from an extreme initial position in order to set the anchor high for your side.
Availability Heuristic: the tendency to assign probabilities of potential outcomes based on examples that are immediately available to us, especially those that are vivid, unusual, or emotionally charged, which are then generalized into conclusions upon which choices are based.
Example: you overestimate the danger of flying due to the number of airplane crashes you see on the news.
Representative Bias: the tendency to judge an event as probable to the extent that it represents the essential features of its parent population or generating process.
Example: "Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice and participated in antinuclear demonstrations."
Which is more likely:
- Linda is a bank teller.
- Linda is a bank teller and is active in the feminist movement.
Before reading further, select an option in your mind. Got it? I will tell you that I selected #2. However, "mathematically speaking, the probability of two events occurring together will always be less than the probability of one occurring by itself." But I, like most people (~85%), fell victim to the representative bias "in which the descriptive terms presented in the second option seemed more representative of the description of Linda."
Inattentional Blindness Bias: the tendency to miss something obvious and general while attending to something special and specific.
Example: the classic video presented to audiences with the instruction to count the number of passes made by each basketball team. 50% of people do not see the man in the gorilla suit (something obvious) walk through the middle of the room during the video because they are focused on counting passes (something specific).
Primacy Effect: the tendency to notice, remember, and assess as more valuable initial events more than subsequent events.
Example: your first kiss.
Projection Bias: the tendency to assume that others share the same or similar beliefs, attitudes, and values, and to overestimate the probability of others' behaviors based on our own behaviors.
Example: smokers tend to overestimate the number of people who smoke.
Self-fulfilling prophecy: the tendency to believe in ideas and to behave in ways that conform to expectations for beliefs and actions.
Example: students who believe they are "smart" tend to do better academically. Students who believe they are "bad at math" tend to get worse grades in math.
Authority bias: the tendency to value the opinions of an authority, especially in the evaluation of somethign we know little about.
Example: the reason I believe most everything Michael Shermer writes.
Bandwagon effect: the tendency to hold beliefs that other people in your social group hold because of the social reinforcement provided.
Example: all your friends buy Apple products, so you purchase a Mac.
Believability bias: the tendency to evaluate the strength of an argument based on the believability of its conclusion.
Example: why the debate team with the more believable conclusion tends to receive better evaluation for the strength of their argument.
Confabulation bias: the tendency to conflate memories with imagination and other people's accounts as one's own.
Example: you think that you had skied Jackson Hole in your youth, when in reality you had only visited Jackson Hole and heard many stories from friends of the great skiing in the area.
Consistency bias: the tendency to recall one's past beliefs, attitudes, and behaviors as resembling present beliefs, attitudes, and behaviors more than they actually do.
Example: I definitely wasn't a hardcore Catholic in high school (I was). I was actually pretty open-minded like I am now (I wasn't).
Expectation bias / experimenter bias: the tendency for observers and especially for scientific experimenters to notice, select, and publish data that agree with their expectation for the outcome of an experiment, and to not notice, discard, or disbelieve data that appear to conflict with those experimental expectations.
Example: we ran an experiment where we were inserting a new gene into E. coli. The results indicated that the gene was successfully inserted, which was great because it was supposed to insert and our grade relied on this result (in reality, the results were a bit iffy).
Barnum effect: the tendency to treat vague and general descriptions of personality as highly accurate and specific.
Example: the reason people believe their daily horoscope.
Clustering illusion: the tendency to see clusters of patterns that, in fact, can be the result of randomness; a form of patternicity.
Example: the reason we can see images in random Rorschach inkblot tests.
False-consensus effect: the tendency for people to overestimate the degree to which others agree with their beliefs or that will go along with them in a behavior.
Example: the reason many coup d'état's (or overthrows) fail.
Halo effect: the tendency for people to generalize one positive trait of a person to all the other traits of that person.
Example: "but he was so kind! There's no way he could have murdered her."
Herd bias: the tendency to adopt the beliefs and follow the behaviors of the majority of members in a group in order to avoid conflict.
Example: probably the reason I was a practicing Catholic until I moved out of my parents' house.
Illusion of control: the tendency for people to believe that they can control or at least influence outcomes that most people cannot control or influence.
Example: probably the reason any of us vote in a presidential election.
Illusory correlation: the tendency to assume that a causal connection (correlation) exists between two variables; another form of patternicity.
Example: "the collapse of the Twin Towers looked like controlled demolitions." To a trained eye, they didn't.
In-group bias: the tendency for people to value the beliefs and attitudes of those whom they perceive to be fellow members of their group, and to discount the beliefs and attitudes of those whom they perceive to be members of a different group.
Example: the reason I right off everything that comes out of Glenn Beck's mouth. It's not necessarily wrong, I'm just biased!
Just-word bias: the tendency for people to search for things that the victim of an unfortunate event might have done to deserve it.
Example: "oh you stubbed your toe? Well you shouldn't have called me an asshole."
Negativity bias: the tendency to pay closer attention and give more weight to negative events, beliefs, and information than to positive.
Example: the news.
Normalcy bias: the tendency to discount the possibility of a disaster that has never happened before.
Example: I've never been in a car accident, so I don't wear my seatbelt. (note: I wear the shit out of my seat belt. That thing saves lives.)
Not-invented-here bias: the tendency to discount the value of a belief or source of information that does not come from within.
Example: "You can teach a man nothing; you can only help him to find it within himself."
Recency effect: the tendency to notice, remember, and assess as more valuable recent events more than earlier events.
Example: the reason history is allowed to repeat itself. We forget.
Rosy retrospection bias: the tendency to remember past events as being more positive than they actually were.
Example: the reason getting back together with your ex seems like a good idea. Well, part of the reason. The other is probably your hormones.
Stereotyping or generalization bias: the tendency to assume that a member of a group will have certain characteristics believed to represent the group without having actual information about that particular member.
Example: I tend to assume that Asians are good at math.
Trait-ascription bias: the tendency for people to assess their own personality, behavior, and beliefs as more variable and less dogmatic than those of others.
Example: the reason I think my scientific beliefs are less dogmatic than Christian doctrine. Are they? Idk now. Questioning it...
Bias blind spot: the tendency to recognize the power of cognitive biases in other people but to be blind to their influence upon our own beliefs.
Example: clearly Bill O'Reilly is biased because he's a Republican. Oh, me? No, I'm not biased. Even though I am generally pretty liberal, I don't let it bias my perceptions. (It biases the shit out of my perceptions.)
The solution to all these biases? Science! But hell, I'm biased. Hahaha.