In the early 1970s, Amos Tversky and Daniel Kahneman raised the awareness of hindsight bias as a pervasive phenomenon in all human judgment.[1] Although these insights seemed eponymously obvious in hindsight, experimental psychologists directly tested the existence and extent of hindsight bias in a now classic paper by Baruch Fischhoff.[2] The lack of awareness of how hindsight bias affects our historical judgments seriously limits our ability to judge the past.
Kahneman’s participation in the planning phase of a new, fourth edition of the Reference Manual on Scientific Evidence, is a hopeful sign that his insights and the research of many psychologists will gain a fuller recognition in the law. Hindsight bias afflicts judges, lawyers, jurors, expert witnesses, scientists, physicians, and children of all ages.[3]
Hindsight Bias in the Law
Sixth Amendment Challenges
Challenges to the effectiveness of legal counsel is a mainstay for habeas petitions, filed by convicted felons. In hindsight, their lawyers’ conduct seems woefully inadequate. In judging such claims of ineffectiveness, the United States Supreme Court acknowledged the role and influence of hindsight bias in judging trial counsel’s strategic decisions:
“A fair assessment of attorney performance requires that every effort be made to eliminate the distorting effects of hindsight, to reconstruct the circumstances of counsel’s challenged conduct, and to evaluate the conduct from counsel’s perspective at the time. Because of the difficulties inherent in making the evaluation, a court must indulge a strong presumption that counsel’s conduct falls within the wide range of reasonable professional assistance; that is, the defendant must overcome the presumption that, under the circumstances, the challenged action might be considered sound trial strategy.”[4]
This decision raises the interesting question why there is not a strong presumption of reasonableness in other legal contexts, such as the “reasonableness” of physician judgments, or of adequate warnings.
Medical Malpractice
There is little doubt that retrospective judgments of the reasonableness of medical decisions is infected, distorted, and corrupted by hindsight bias.[5] In the words of one paper on the subject:
“There is evidence that hindsight bias, which may cause the expert to simplify, trivialise and criticise retrospectively the decisions of the treating doctor, is inevitable when the expert knows there has been an adverse outcome.”[6]
Requiring the finder of fact to assess the reasonableness of complex medical judgments in hindsight, with knowledge of the real-world outcomes of the prior judgments, pose a major threat to fairness in the trial process, in both bench and jury trials. Curiously, lawyers receive a “strong presumption” of reasonableness, but physicians and manufacturers do not.
Patent Litigation
Hindsight bias plays a large role in challenging patent validity. The works of genius seem obvious with hindsight. In the context of judging patent criteria such non-obviousness, the Supreme Court has emphasized that:
“A factfinder should be aware, of course, of the distortion caused by hindsight bias and must be cautious of arguments reliant upon ex post reasoning.”[7]
Certainly, factfinders in every kind of litigation, not just intellectual property cases, should be made aware of the distortion caused by hindsight bias.
Remedies
In all likelihood, hindsight bias can probably never be fully corrected. At a minimum, factfinders should be educated about the phenomenon. In criminal cases, defendants have called psychologists about the inherent difficulties in eyewitness or cross-race identification.[8] In New Jersey, trial courts must give a precautionary instruction in criminal cases that involve eyewitness identification.[9] In some but not all discrimination cases, courts have permitted expert witness opinion testimony about “implicit bias.”[10] In “long-tail” litigation, in which jurors must consider the reasonableness of warning decisions, or claims of failure to test, decades before the trial, defendants may well want to consider calling a psychologist to testify about the reality of hindsight bias, and how it leads to incorrect judgments about past events.
Another, independent remedy would be for the trial court to give a jury instruction on hindsight bias. After all, the Supreme Court has clearly stated that “[a] factfinder should be aware, of course, of the distortion caused by hindsight bias and must be cautious of arguments reliant upon ex post reasoning.” The trial judge should set the stage for a proper consideration of past events, by alerting jurors to the reality and seductiveness of hindsight bias. What follows is a first attempt at such an instruction. I would love to hear from anyone who has submitted a proposed instruction on the issue.
Members of the jury, this case will require your determination of what were the facts of what scientists knew or should have known at a time in the past. At the same time that you try to make this determination, you will have been made aware of what is now known. Psychological research clearly shows that all human beings, regardless of their age, education, or life circumstances have what is known as hindsight bias. Having this bias means that we all tend to assume that people at times past should have known what we now in fact know. Calling it a bias is a way to say that this assumption is wrong. To decide this case fairly, you must try to determine what people, including experts in the field, actually knew and did before there were more recent discoveries, and without reference to what is now known and accepted.
[1] Amos Tversky & Daniel Kahneman, “Judgment under uncertainty: heuristics and Biases,” 185 Science 1124 (1974). See also “People Get Ready – There’s a Reference Manual a Comin’ ”(June 6, 2021).
[2] Baruch Fischhoff, “Hindsight ≠ foresight: the effect of outcome knowledge on judgment under uncertainty,” 1 Experimental Psychology: Human Perception & Performance 288, 288 (1975), reprinted in 12 Quality & Safety Health Care 304 (2003); Baruch Fischhoff & Ruth Beyth, “I knew it would happen: Remembered probabilities of once – future things?” 13 Organizational Behavior & Human Performance 1 (1975); see Baruch Fischhoff, “An Early History of Hindsight Research,” 25 Social Cognition 10 (2007).
[3] See Daniel M. Bernstein, Edgar Erdfelder, Andrew N. Meltzoff, William Peria & Geoffrey R. Loftus, “Hindsight Bias from 3 to 95 Years of Age,” 37 J. Experimental Psychol., Learning, Memory & Cognition, 378 (2011).
[4] Strickland v. Washington, 466 U.S. 668, 689, 104 S.Ct. 2052, 2052 (1984); see also Feldman v. Thaler, 695 F.3d 372, 378 (5th Cir. 2012).
[5] Edward Banham-Hall & Sian Stevens, “Hindsight bias critically impacts on clinicians’ assessment of care quality in retrospective case note review,” 19 Clinical Medicine 16 (2019); Thom Petty, Lucy Stephenson, Pierre Campbell & Terence Stephenson, “Outcome Bias in Clinical Negligence Medicolegal Cases,” 26 J.Law & Med. 825 (2019); Leonard Berlin, “Malpractice Issues and Radiology – Hindsight Bias” 175 Am. J. Radiol. 597 (2000); Leonard Berlin, “Outcome Bias,” 183 Am. J. Radiol. 557 (2004); Thomas B. Hugh & Sidney W. A. Dekker, “Hindsight bias and outcome bias in the social construction of medical negligence: a review,” 16 J. Law. Med. 846 (2009).
[6] Thomas B. Hugh & G. Douglas Tracy, “Hindsight Bias in Medicolegal Expert Reports,” 176 Med. J. Australia 277 (2002).
[7] KSR International Co. v. Teleflex Inc., 550 U.S. 398, 127 S.Ct. 1727, 1742 (2007) (emphasis added; internal citations omitted).
[8] See Commonwealth v. Walker, 92 A.3d 766 (Pa. 2014) (Todd, J.) (rejecting per se inadmissibility of eyewitness expert witness opinion testimony).
[9] State v. Henderson, 208 N.J. 208, 27 A.3d 872 (2011).
[10] Samaha v. Wash. State Dep’t of Transp., No. cv-10-175-RMP, 2012 WL 11091843, at *4 (E.D. Wash. Jan. 3, 2012) (holding that an expert witness’s proferred opinions about the “concepts of implicit bias and stereotypes is relevant to the issue of whether an employer intentionally discriminated against an employee.”).
