Structures of both languages were compared pattern by pattern. Much of the conventional criticism says that many of the predicted differences and difficulties did not turn out to be difficulties, and vice versa, many of the learners expected difficulties were not anticipated. Lado himself admitted that continuous work and research has to be done on the hypothetical problems in order to get a final validation. Major projects have been done in Europe before Lado's theory was published. One of them compared German and English at Kiel, another one is known as the PAKS project which compared Polish and English at Posnan, and also Finnish and English at Jyvaskyla have been target of a research project.
Phonology is considered as a list of phonemes and allophones.
Lado saw grammar as structures, such as the word order of questions, the use of intonation and pauses for grammatical effect, and morphology such as English third-person s . Furthermore, he related the two languages at levels of vocabulary and culture. There is some limitation to this type of analysis and this view of a phrase. Another strand in Lado's theory is the model of language learning. Habits are based on laws of language learning such as exercise, familiarity of response.