The virtues of ignorance.

Although ignorance and uncertainty are usually unwelcome feelings, they have unintuitive advantages for both human and non-human animals, which we review here. We begin with the perils of too much information: expertise and knowledge can come with illusions (and delusions) of knowing. We then describe how withholding information can counteract these perils: providing people with less information enables them to judge more precisely what they know and do not know, which in turn enhances long-term memory. Data are presented from a new experiment that illustrates how knowing what we do not know can result in helpful choices and enhanced learning. We conclude by showing that ignorance can be a virtue, as long as it is recognized and rectified. Copyright 2009 Elsevier B.V. All rights reserved.