Various forms of uncertainty are important for decision making. How aware are we of the precision of knowledge, and how accessible it is? In three experiments, an assessment of the precision of spatial memory was needed to make optimal decisions. First, we examined search strategies in a search task in which the most efficient strategy was to head to one side of the target by a margin depending on the precision of spatial information, the "where to start" task. We found that nine out of of our 20 human subjects adapted the margin according to precision. Second, we let the subjects search for the location of a sample picture. On one-third of the trials, the target was not present, making it a "when to stop searching" task. We found that the subjects did not adjust their investment in search according to their precision. In the third experiment, we looked at whether there was transfer between the two tasks. Subjects who had been reminded of the relevance of uncertainty by the "where to start" task increased their search effort more in the "when to stop searching" task. Thus, the results show that the use of information about precision is not automatic, but can be triggered.