We investigated example choice as a new method for the teaching of formal theoretical principles. Formal principles are presented with several examples from different topics, and students choose the one that interests them most. Example choice might be related to prior knowledge, interest, or perceived control. In an experimental study, we examined the effects of degree of example choice and degree of prior knowledge on interest, perceived control, and learning outcomes in a presentation on confirmation bias. The main finding was that participants who could choose an example showed more interest in the presentation of the formal principle than participants who either were given an example by the experimenter or only saw the presentation. Control was lowest for the group without example choice and without prior knowledge. Finally, prior knowledge, but not example choice, increased performance on a transfer of knowledge task. Example choice thus offers a new approach for closing the gap between formal principles as presented at school and a student's interests.