Subadditivity in memory for personal events

People's subjective probability judgments of external events are often suba dditive (Le., the probability estimates of component parts of a single even t sum to greater than one)-a clear violation of the extensional nature of p robability theory. We show that people's frequency judgments of personal ev ents can also be subadditive. We found subadditivity evert when component e vents made up a proper subset of a wider composite event. Our findings impl y that the somewhat arbitrary choice of the specificity with which question s are asked can produce widely different reports for the same composite eve nts.