The strong version of the contrastive analysis hypothesis is associated with Charles Fries and Robert Lado. It predicts that second language learners will have difficulty with aspects (structures, or vocabulary) which differ from their first language, and conversely no problems with aspects which are similar in their first language.
Individuals tend to transfer the forms and meanings, and the distribution of forms and meanings of their native language and culture to the foreign language and culture - both productively when attempting to speak the language and to act in the culture, and receptively when attempting to grasp and understand the language and the culture as practised by natives. . . . [It assumes] that the student who comes in contact with a foreign language will find some features of it quite easy and others extremely difficult. Those elements that are similar to his native language will be simple for him, and those elements that are different will be difficult.