“Don’t Know†Responses, Personality, and the Measurement of Political Knowledge

A prominent worry in the measurement of political knowledge is that respondents who say they don’t know the answer to a survey question may have partial knowledge about the topic—more than respondents who answer incorrectly but less than those who answer correctly. It has also been asserted that differentials in respondents’ willingness to guess, driven strongly by personality, can bias traditional knowledge measures. Using a multinomial probit item response model, I show that, contrary to previous claims that “don’t know†responses to political knowledge questions conceal a good deal of “hidden knowledge,†these responses are actually reflective of less knowledge, not only than correct responses but also than incorrect answers. Furthermore, arguments that the meaning of “don’t know†responses varies strongly by respondent personality type are incorrect. In fact, these results hold for high- and low-trait respondents on each of the five most commonly used core personality measures.