In Brazil the hardest part seems to be listening comprehension.

I think that a judgment about which parts of EFL are most difficult depends in large part on how close or distant the target language is from the first language.  For instance, the Romance languages of Western Europe are derived from Latin and 70% of English vocabulary has come from Latin by way of Norman French/English.  Therefore, students often find vocabulary, listening and reading much easier than do the students whose languages have no affinity with the Indo-European language group. Speaking skills may be a bit difficult until they adjust to the rhythms of American English (or whatever other languages they are learning).

But for students whose first languages are Arabic and Chinese (students I work with frequently in ESL classes), there is much more difficulty in every aspect of learning English. Not only do we have no language history in common, but we also have no rhetorical similarities in our style of writing and presentation.  If these students are also students in an American university and trying to master Academic English, the problems can be much more difficult since that level of English is, in reality, a different language from spoken and even formal written English.  On the TOEFL exams, these students have difficulties with every section--reading, listening, and speaking.

Once these students have been on campus and around native-American English speakers, their abilities in listening and speaking sections dramatically improve.  Their ear for the rhythm and style of English has improved and many have become more familiar with American-style textbooks and the writing style of those texts. 

But no matter where a student comes from or what language he/she speaks, ultimately the hardest problem confronting any student learning another language and/or living in that unfamiliar culture is learning the culture.  Without access to the culture, the language remains even more difficult. Even the tone of our voice and the inflection present is culturally determined.  It is a tough task to learn any second or third language but it remains one of the most fascinating experiences one can have.

Aysha

I have even noticed that thew Farsi-speakers seem to have less trouble with vocabulary and writing skills than do my Arabic-speaking students.  Although Farsi certainly is not written with Roman letters, it is a member of the Indo-European family of languages; perhaps that common linguistic background has something to do with this difference.  I don't know of any studies in this subject matter, but it is an interesting point, I think.

What i have been experience through out my study is in speaking. Language  required practice, without it will died, I failed to exercise English when living with my own people. Our mother tongue always be a domain language for all conversations. But all start change when i meet numerous foreign friends from various country with different language and we all force to speak English to get interact each other.  

Siti, I absolutely agree that access to those who speak the target language is highly determinate in learning to speak and understand that language. I often have students who enter the U.S. and want to take the TOEFL exam quickly; I usually advise them to wait a few months and spend time on campus, take an ESL class in English and get to speak with classmates and others to gain the "ear" for listening on the test. Their own speaking improves as well because they can hear and imitate the sounds and rhythms of the English they hear (and here in Alabama, I had trouble for months when I first arrived because these people sounded like they had marbles in their mouths).  I am from Pennsylvania and grew up speaking English and German; Southerners speak English but when I first arrived, what I heard did not sound much like English.  Now when I go back home, people ask me what part of the South I am from!  Obviously, my accent has changed with the people around me. 

One of the greatest things about a campus with international students is getting to talk with them, learn more about them, and at times learn more of their language. 

Aysha

Aysha -- your description of the American accent in the South makes me smile.  But you point about improving ability through using the language is right on target.

I think for my learners here in Japan, the hardest part is making the language come alive. It is basically just another school subject here, so students need a way to connect it with real life and to make it something they have an authentic reason to use as a living language.