Fact and fantasy: The effects of internally generated events on the apparent frequency of externally generated events.

As John Locke pointed out, there are at least two sources of the contents of the mind: events that occur in the world and events that originate in the mind. Memory, as a record of experience, should contain information from both sources. The present studies investigated memory for the frequency of externally and internally generated events. Individual items were presented to subjects varying numbers of times and tested varying numbers of times. Later, subjects were asked to estimate the frequency of both types of events. Experiment 1 showed that internally generated events influenced the judged frequency of externally generated events and vice versa. The first of these was called the IFE effect and the second the IFI effect. Experiment 2 indicated that the IFE effect was greater when tests consisted of overt, as compared to covert, recall trials. The results were discussed in terms of a model for storing and using occurrence information which would account for both our ability to discriminate between and our tendency to confuse internally and externally generated memory representations.