Studies of inference from lack of knowledge.

Two experiments were performed to investigate the conditions affecting lack-of-knowledge inferences. The lack-of-knowledge inference is a metainference, an inference based on knowledge about one's own knowledge, in which the absence of information concerning a possible assertion is taken as evidence that the assertion is false. In Experiment 1, it was shown that lack of knowledge about an assertion decreases subjects' ratings of the likelihood that the assertion is true. The more important the assertion and the more expert the person who lacks knowledge, the more certain is the lack-of-knowledge inference, as measured by a decrease in the rated likelihood of the assertion. In Experiment 2, a hypothesis about the nature of self-judgments of expertise was tested. This intrinsic observation hypothesis states that expertise relevant to an assertion is determined by the number of similar assertions from the same domain that the person can retrieve. The hypothesis was ruled out by the results of Experiment 2. Other possibilities for the manner in which self judgments of this kind are made are discussed.