Bias: systematic distortion of a result arising from a neglected factor. (Oxford) A tendency to treat one individual or group in a different way to others. Bias can be positive or negative. In ("experimental design") we may have biased samples, such that the underlying population is not appropriately sampled. (Cardwell, 31)

Our biological instincts are not always very well adapted to the information-rich modern world. Unless we work actively to become aware of the bias we introduce, the returns to additional information may be minimal - or diminishing. (Silver, 13) Robert Burton says it should be a red flag whenever anyone claims that they had no a-priori assumptions. He concludes that complete objectivity is not possible. The best we can hope for is partial objectivity, which means acknowledging our biases and assumptions as accurately and honestly as we can. (Campbell, 22)  The word ‘objective’ is sometimes taken to be synonymous with ‘quantitative,’ but it isn’t. Instead it means seeing beyond our personal biases and prejudices and toward the truth of a problem. (Silver, 72)

Attributional Bias: the tendency to depart from the rules of attribution in establishing the causes of behavior. (Cardwell, 21) Biases and errors that people will commonly default to as they try to find a reason for behavior. (Kleinman, 167)

Self-Effacing Bias: (the tendency) to downplay our successes by attributing them to external causes (and) to blame ourselves for our failures. This is most common in “collectivist cultures.” (Hockenbury, 446) Also referred to as ‘modesty bias.’

Self-Serving Bias: the tendency to attribute one's success to internal causes and one's failures to external causes. (Floyd, G5) (Taking) personal responsibility for successes, while denying personal responsibility for failures. (Bamford, 11/30/10) To attribute our positive actions and successes to stable, global, internal influences under our control, and to attribute our negative actions and failures to unstable, specific, external influences beyond our control. (Wood 336) Editor's note - this is most common in “individualistic cultures.”

Belief-Bias Effect: occurs when people accept only the evidence that conforms to their belief, rejecting or ignoring any evidence that does not. (Hockenbury, 270)

Confirmation Bias: the tendency to seek information that supports our values and beliefs, while discounting or ignoring information that doesn't. (Floyd, G2) To search for information or evidence that confirms a belief, while making little or no effort to search for information that might disprove the belief. (Hockenbury, 270)

Gender Bias: refers to the treatment of men and women in psychological research. Many theories are based on a study of males only and therefore might offer an interpretation of women based on an understanding of the lives of men. (Cardwell, 112)

Alpha Bias: theories that see real differences between men and women, and may represent either an enhancement or undervaluing of one gender compared to the other. Freud’s ("psychoanalytic theory") is an example of an alpha bias theory that undervalues women. (Cardwell, 112)

Beta Bias: theories that ignore or minimize differences between men and women. (Cardwell, 112)

Hindsight Bias: the tendency to overestimate one’s ability to have foreseen or predicted the outcome of an effect. (Hockenbury, 464)

Ingroup Bias: the tendency to judge the behavior of ingroup members favorable and outgroup members unfairly. (Hockenbury, 452)

Negative Bias: unfavorable behavior is shown toward the recipient of the bias. (Cardwell, 31)

Observer Bias: the tendency of an observer to distort observations or perceptions to match his or expectations. (Coon, 33) The tendency for observers who are aware of the “hypothesis” under test to see and record what might be expected, rather than what actually happens. To guard against this, we can use observers who have no knowledge of the predictions being made. (Cardwell, 167)

Outgroup Homogeneity Effect: the tendency to see members of (an) outgroup as very similar to one another. (Hockenbury, 452)

Overestimation Effect: the tendency to overestimate the rarity of events. (Hockenbury, 270)

Positive Bias: favorable behavior is shown toward the recipient of the bias. (Cardwell, 31) Also, a tendency for first impressions of others to be more positive than negative. (McCornack, 98) Also referred to as ‘positivity bias.’

Sample Bias: refers to the overrepresentation of one category of participant (males, females, students, people of a certain age, etc.) in a sample so that the sample fails to adequately represent the population from which it was taken. (Cardwell, 31) An error in choosing the individuals or groups to take part in a study. Ideally, the subjects in a study should be very similar to one another and to the larger population from which they are drawn (for example, all individuals with the same disease or condition). If there are important differences, the results of the study may not be valid. (NCIt) Also referred to as ‘sampling bias’ and ‘biased sampling.’

Law of Small Numbers: the belief that results based on small samples are representative of the larger population. With this bias, individuals often draw general conclusions based on a few individual cases. (Bamford, 10/18/10)