Through this research, he identified three factors that could be used to calculate language learning aptitude: verbal intelligence, auditory ability, and motivation. Pimsleur was the primary author of the Pimsleur Language Aptitude Battery (PLAB) based on these three factors to assess language aptitude. He concluded that low auditory ability was a major factor in underachievement. Pimsleur was one of the first foreign language educators to show an interest in students who have difficulty in learning a foreign language while doing well in other subjects. Today, the PLAB is used to determine foreign language-learning aptitude, or even a foreign language-learning disability, among secondary-school students.