The aim of this paper is to investigate how evidentials are used to reflect the unprepared mind of the speaker. Lexical evidentials are typically used by speakers to encode the kinds of evidence they have for making statements about states, events and actions they did not personally witness or were a part of. However, under certain conditions evidentials can be used to express the surprise of the speaker. This is known in the literature under the label mirativity. The empirical factors that condition the mirative use of an evidential are first determined, and then using an information and schema-theoretic analysis it is shown that mirativity is the linguistic reflex of a series of mental events involving the processing of new information, coupled with other contextual factors involving speaker knowledge.