translation.en: Sometime later -- it could be 15 minutes; it could be 15 days -- the same stimuli are put before the subject, and the subject is asked to re-rank the stimuli.
translation.zh: 过了一段时间之后 - 这可能是15分钟，也可能是15天。 对同样的画， 我们叫受试者对同样的画再一次排序。