The “availability heuristic” – a pervasive cognitive bias caused by people’s tendency to estimate the likelihood of a phenomenon by how easily an example of it comes to mind – routinely clouds the issue. People relate much more readily to a friend dying of cancer than they do to statistics about strangers suffering from the consequences of testing.
由于人类倾向于通过联想起相关事例的难易程度来评估一种情况出现的可能性，而这种认知偏好又是普遍存在的——也就是所谓的“可用性启发（availability heuristic）”，通常会令事情变得更加模糊不清。相对于一个陌生人因为筛查测试而受苦的统计概率，人们更容易联想起一个挣扎在癌症死亡线上的熟人。