BRGHT uses Item Response Theory (IRT) models because the brght IQ test is adaptive, which means that different types of questions are answered by different types of users. For example, easy questions are mainly answered by people with a slightly lower IQ, while difficult questions (with a high item difficulty) are only answered by people with a higher IQ.

Using traditional methods, such as looking at the percentage of people who answered a question correctly, would not be sufficient to determine the difficulty of a question, as the question may have only been answered by people with very high or low IQs. IRT models, on the other hand, take into account all responses from all users, allowing BRGHT to accurately determine how difficult a question is and how much it tells about a specific person's IQ.