In psychologyandcognitive science, a memory bias is a cognitive bias that either enhances or impairs the recall of a memory (either the chances that the memory will be recalled at all, or the amount of time it takes for it to be recalled, or both), or that alters the content of a reported memory. There are many different types of memory biases, including:
Availability bias: greater likelihood of recalling recent, nearby, or otherwise immediately available examples, and the imputation of importance to those examples over others
Boundary extension: remembering the background of an image as being larger or more expansive than the foreground 
Choice-supportive bias: remembering chosen options as having been better than rejected options (Mather, Shafir & Johnson, 2000)
Confirmation bias: the tendency to search for, interpret, or recall information in a way that confirms one's beliefs or hypotheses.
Conservatism or Regressive bias: tendency to remember high values and high likelihoods/probabilities/frequencies lower than they actually were and low ones higher than they actually were. Based on the evidence, memories are not extreme enough.
Consistency bias: incorrectly remembering one's past attitudes and behaviour as resembling present attitudes and behaviour.
Context effect: that cognition and memory are dependent on context, such that out-of-context memories are more difficult to retrieve than in-context memories (e.g., recall time and accuracy for a work-related memory will be lower at home, and vice versa).
Cryptomnesia: a form of misattribution where a memory is mistaken for imagination, because there is no subjective experience of it being a memory.
Egocentric bias: recalling the past in a self-serving manner, e.g., remembering one's exam grades as being better than they were, or remembering a caught fish as bigger than it really was.
Fading affect bias: a bias in which the emotion associated with unpleasant memories fades more quickly than the emotion associated with positive events.
Generation effect (Self-generation effect): that self-generated information is remembered best. For instance, people are better able to recall memories of statements that they have generated than similar statements generated by others.
Hindsight bias: the inclination to see past events as being predictable; also called the "I-knew-it-all-along" effect.
Humor effect: that humorous items are more easily remembered than non-humorous ones, which might be explained by the distinctiveness of humor, the increased cognitive processing time to understand the humor, or the emotional arousal caused by the humor.
Illusion-of-truth effect: that people are more likely to identify as true statements those they have previously heard (even if they cannot consciously remember having heard them), regardless of the actual validity of the statement. In other words, a person is more likely to believe a familiar statement than an unfamiliar one.
Leveling and sharpening: memory distortions introduced by the loss of details in a recollection over time, often concurrent with sharpening or selective recollection of certain details that take on exaggerated significance in relation to the details or aspects of the experience lost through leveling. Both biases may be reinforced over time, and by repeated recollection or re-telling of a memory.
Levels-of-processing effect: that different methods of encoding information into memory have different levels of effectiveness (Craik & Lockhart, 1972).
List-length effect: a smaller percentage of items are remembered in a longer list, but as the length of the list increases, the absolute number of items remembered increases as well.
Memory inhibition: that being shown some items from a list makes it harder to retrieve the other items (e.g., Slamecka, 1968).
Misattribution of memory: when information is retained in memory but the source of the memory is forgotten. One of Schacter's (1999) seven sins of memory, misattribution was divided into source confusion, cryptomnesia and false recall/false recognition.
Reminiscence bump: the recalling of more personal events from adolescence and early adulthood than personal events from other lifetime periods (Rubin, Wetzler & Nebes, 1986; Rubin, Rahhal & Poon, 1998).
Saying is Believing effect: Communicating a socially tuned message to an audience can lead to a bias of identifying the tuned message as one's own thoughts.
Self-reference effect: the phenomena that memories encoded with relation to the self are better recalled than similar information encoded otherwise.
Self-serving bias: perceiving oneself responsible for desirable outcomes but not responsible for undesirable ones.
Source confusion: misattributing the source of a memory, e.g. misremembering that one saw an event personally when actually it was seen on television.
Spacing effect: that information is better recalled if exposure to it is repeated over a longer span of time.
Stereotypical bias: memory distorted towards stereotypes (e.g. racial or gender), e.g. "black-sounding" names being misremembered as names of criminals.
Subadditivity effect: the tendency to estimate that the likelihood of a remembered event is less than the sum of its (more than two) mutually exclusive components.
Suffix effect: the weakening of the recency effect in the case that an item is appended to the list that the subject is not required to recall (Morton, Crowder & Prussin, 1971).
Suggestibility: a form of misattribution where ideas suggested by a questioner are mistaken for memory.
Telescoping effect: the tendency to displace recent events backward in time and remote events forward in time, so that recent events appear more remote, and remote events, more recent.
Testing effect: that frequent testing of material that has been committed to memory improves memory recall.
Tip of the tongue: when a subject is able to recall parts of an item, or related information, but is frustratingly unable to recall the whole item. This is thought to be an instance of "blocking" where multiple similar memories are being recalled and interfere with each other.
Verbatim effect: that the "gist" of what someone has said is better remembered than the verbatim wording (Poppenk, Walia, Joanisse, Danckert, & Köhler, 2006).
Von Restorff effect: that an item that sticks out is more likely to be remembered than other items (von Restorff, 1933).
Zeigarnik effect: that uncompleted or interrupted tasks are remembered better than completed ones.
Recall bias – Systematic error caused by differences in the accuracy or completeness of the recollections retrieved
Stereotype – Generalized belief about a particular category of people
^Ba, McDunn; Ap, Siddiqui; Jm, Brown (April 2014). "Seeking the Boundary of Boundary Extension". Psychonomic Bulletin & Review. 21 (2): 370–5. doi:10.3758/s13423-013-0494-0. PMID23921509. S2CID 2876131. Retrieved 2020-05-29.
^Attneave, F (1953). "Psychological probability as a function of experienced frequency". Journal of Experimental Psychology. 46 (2): 81–86. doi:10.1037/h0057955. PMID13084849.
^Fischhoff, B.; Slovic, P.; Lichtenstein, S. (1977). "Knowing with certainty: The appropriateness of extreme confidence". Journal of Experimental Psychology: Human Perception and Performance. 3 (4): 552–564. doi:10.1037/0096-15126.96.36.1992.
^ abcdSchacter, Daniel L. (1999). "The Seven Sins of Memory: Insights From Psychology and Cognitive Neuroscience". American Psychologist. 54 (3): 182–203. doi:10.1037/0003-066X.54.3.182. PMID10199218.
^Walker, W. Richard; John J. Skowronski; Charles P. Thompson (2003). "Life Is Pleasant—and Memory Helps to Keep It That Way!" (PDF). Review of General Psychology. 7 (2): 203–210. doi:10.1037/1089-26188.8.131.52. S2CID 43179740. Archived from the original (PDF) on January 24, 2011. Retrieved 2009-08-27.
^Fiedler, K (1991). "The tricky nature of skewed frequency tables: An information loss account of distinctiveness-based illusory correlations". Journal of Personality and Social Psychology. 60 (1): 24–36. doi:10.1037/0022-35184.108.40.206.
^Koriat, A.; M. Goldsmith; A. Pansky (2000). "Toward a Psychology of Memory Accuracy". Annual Review of Psychology. 51 (1): 481–537. doi:10.1146/annurev.psych.51.1.481. PMID10751979.
^Nelson, D. L.; U. S. Reed; J. R. Walling (1976). "Pictorial superiority effect". Journal of Experimental Psychology: Human Learning & Memory. 2 (5): 523–528. doi:10.1037/0278-73220.127.116.113. PMID1003125.
^Kruger, J.; Dunning, D. (1999). "Unskilled and unaware of it: How difficulties in recognizing one's own incompetence lead to inflated self-assessments". Journal of Personality and Social Psychology. 77 (6): 1121–1134. CiteSeerX10.1.1.64.2655. doi:10.1037/0022-3518.104.22.1681. PMID10626367.
^Kruger, J. (1999). Lake Wobegon be gone! The "below-average effect" and the egocentric nature of comparative ability judgments" Journal of Personality and Social Psychology 77(2),
^ abMartin, G. Neil; Neil R. Carlson; William Buskist (2007). Psychology (3rd ed.). Pearson Education. pp. 309–310. ISBN 978-0-273-71086-8.
^Tversky, A.; Koehler, D. J. (1994). "Support theory: A nonextensional representation of subjective probability" (PDF). Psychological Review. 101 (4): 547–567. doi:10.1037/0033-295X.101.4.547.
Greenwald, A (1980). "The Totalitarian Ego: Fabrication and Revision of Personal History" (PDF). American Psychologist. 35 (7): 603–618. doi:10.1037/0003-066X.35.7.603.
Schacter, D. L.; Chiao, J. Y.; Mitchell, J. P. (2003). "The Seven Sins of Memory. Implications for Self" (PDF). Annals of the New York Academy of Sciences. 1001 (1): 226–239. Bibcode:2003NYASA1001..226S. doi:10.1196/annals.1279.012. PMID14625363. S2CID 144885545.
Media related to Memory biases at Wikimedia Commons