如果你曾经感觉情况非常熟悉，即使你知道它根本不熟悉，比如你是第一次在城市旅行，那么你可能已经体验过似曾相识。 Déjàvu，意思是“已经在法语中看到”，它结合了客观的不熟悉 – 你知道，基于充分的证据，有些东西不应该熟悉 – 主观熟悉 – 无论如何感觉它是熟悉的。 Déjàvu很常见。根据2004年发表的一篇论文，50多项关于似曾相识的调查表明，大约三分之二的人在其一生中至少经历过一次，其中许多人报告了多种经历。随着人们越来越意识到似曾相识的情况，这个报道的数字似乎也在增长。大多数情况下，似曾相识是根据你看到的东西来描述的，但它并不是特定于视觉，即使是天生失明的人也可以体验它。 Déjàvu很难在实验室学习，因为它是一种短暂的体验，也因为没有明确可识别的触发器。然而，研究人员根据他们提出的假设，使用了几种工具来研究这种现象。研究人员可以调查参与者;研究可能相关的过程，特别是那些涉及记忆的过程或设计其他实验来探测似曾相识。因为似曾相识很难测量，研究人员已经假设了许多解释它是如何工作的。以下是一些比较突出的假设。
If you have ever felt that the situation is very familiar, even if you know that it is not familiar at all, for example, if you are traveling in the city for the first time, then you may have experienced deja vu. Déjàvu, meaning “already seen in French”, combines objective unfamiliarity – you know, based on sufficient evidence, something should not be familiar – subjectively familiar – no matter how it feels familiar. Déjàvu is very common. According to a paper published in 2004, more than 50 surveys of deja vu have shown that about two-thirds of people have experienced at least once in their lives, many of whom have reported multiple experiences. As people become more aware of the situation of deja vu, the number of this report seems to be growing. In most cases, deja vu are described in terms of what you see, but it is not specific to the vision, and even a blind person can experience it. Déjàvu is hard to learn in the lab because it is a short-lived experience and because there are no clearly identifiable triggers. However, the researchers used several tools to study this phenomenon based on their assumptions. Researchers can investigate participants; research possible processes, especially those involving memory or design other experiments to detect deja vu. Because familiarity is difficult to measure, researchers have assumed many explanations of how it works. Here are some of the more prominent assumptions.