Original Article

Journal of General Internal Medicine

, Volume 22, Issue 9, pp 1231-1238

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Implicit Bias among Physicians and its Prediction of Thrombolysis Decisions for Black and White Patients

  • Alexander R. GreenAffiliated withThe Disparities Solutions Center, Massachusetts General Hospital, Harvard Medical School Email author 
  • , Dana R. CarneyAffiliated withDepartment of Psychology, Harvard University
  • , Daniel J. PallinAffiliated withBrigham and Women’s Hospital, Harvard Medical School
  • , Long H. NgoAffiliated withBeth Israel Deaconess Medical Center, Harvard Medical School
  • , Kristal L. RaymondAffiliated withUniversity of North Carolina–Chapel Hill
  • , Lisa I. IezzoniAffiliated withBeth Israel Deaconess Medical Center, Harvard Medical School
  • , Mahzarin R. BanajiAffiliated withDepartment of Psychology, Harvard University



Studies documenting racial/ethnic disparities in health care frequently implicate physicians’ unconscious biases. No study to date has measured physicians’ unconscious racial bias to test whether this predicts physicians’ clinical decisions.


To test whether physicians show implicit race bias and whether the magnitude of such bias predicts thrombolysis recommendations for black and white patients with acute coronary syndromes.

Design, Setting, and Participants

An internet-based tool comprising a clinical vignette of a patient presenting to the emergency department with an acute coronary syndrome, followed by a questionnaire and three Implicit Association Tests (IATs). Study invitations were e-mailed to all internal medicine and emergency medicine residents at four academic medical centers in Atlanta and Boston; 287 completed the study, met inclusion criteria, and were randomized to either a black or white vignette patient.

Main Outcome Measures

IAT scores (normal continuous variable) measuring physicians’ implicit race preference and perceptions of cooperativeness. Physicians’ attribution of symptoms to coronary artery disease for vignette patients with randomly assigned race, and their decisions about thrombolysis. Assessment of physicians’ explicit racial biases by questionnaire.


Physicians reported no explicit preference for white versus black patients or differences in perceived cooperativeness. In contrast, IATs revealed implicit preference favoring white Americans (mean IAT score = 0.36, P < .001, one-sample t test) and implicit stereotypes of black Americans as less cooperative with medical procedures (mean IAT score 0.22, P < .001), and less cooperative generally (mean IAT score 0.30, P < .001). As physicians’ prowhite implicit bias increased, so did their likelihood of treating white patients and not treating black patients with thrombolysis (P = .009).


This study represents the first evidence of unconscious (implicit) race bias among physicians, its dissociation from conscious (explicit) bias, and its predictive validity. Results suggest that physicians’ unconscious biases may contribute to racial/ethnic disparities in use of medical procedures such as thrombolysis for myocardial infarction.


unconscious bias thrombolysis race clinical decisions disparities