2. Language learning aptitude
Language learning aptitude refers to the “prediction of how well, relative to other individuals, an individual can learn a foreign language in a given amount of time and under given conditions.

3. John B. Carroll: The four ability components
Definition
Phonetic coding ability
ability to perceive distinct sounds, associate a symbol with that sound and retain that association
Grammatical memory
ability to recognize the grammatical function of a lexical element (word, phrase, etc.) in a sentence without explicit training in grammar
associative memory
ability to learn associations between words in a foreign language and their meanings and retain that association
Inductive learning ability
ability to infer or induce rules governing the structure of a language :

4. Aptitude Test Aptitude Measurements Measurement Description
Modern Language Aptitude Test
mainly authored by John B. Carroll, appropriate for adults, mainly used by government and military institutions to select and place employees for language training
Defense Language Aptitude Battery
developed and used by the United States Department of Defense to select candidates for jobs that will require them to attain fluency in a foreign language
Pimsleur Language Aptitude Battery
authored by Paul Pimsleur, used to assess the language learning aptitude of students in grades 7 to 12
Modern Language Aptitude Test – Elementary
mainly authored by John B. Carroll, appropriate for children in grades 3 to 6
Cognitive Ability for Novelty in Acquisition of Language - Foreign
developed by Grigorenko, Sternberg, and Ehrman in 2000, using a new concept of language aptitude as a theoretical base