Prior knowledge can have a large influence on recall when the memory for the original event is error prone or incomplete. We investigated the interaction between memory and prior knowledge in a recall task involving natural objects such as fruits and vegetables. We first quantified prior knowledge for the sizes of objects in a norming experiment. We then assessed the influence of prior knowledge in a memory experiment in which we compared the actual size of objects shown during a study phase with the reconstructed size of an object during the test phase. Recall was biased both by the mean size of the specific object studied and by the mean size of all objects in the category. This result suggests that the influence of prior knowledge can come from multiple, hierarchically related levels of representation, such as the object-category and superordinate-category levels.