This paper discusses the differences between multiple-choice and open-ended formats for measuring crystallized intelligence or declarative fact knowledge, respectively. It has been suggested that multiple-choice formats only require recognizing the correct response, whereas open-ended formats require cognitive processes such as searching, retrieving, and actively deciding on a response from long-term memory. Two online studies were conducted to test these assumptions, and the results showed that item difficulty increases in the open-ended methods, but the method of inquiry does not affect what is measured with different response formats. This suggests that crystallized intelligence does not change as a function of the response format.