A researcher using secondary data would not have the same insights into the process of conducting research. The usefulness of secondary research tends to be limited often for two main reasons: lack of relevance and lack of accuracy. Secondary research rarely provides all the answers you need. The objectives and methodology used to collect the secondary data may not be appropriate for the problem at hand. Given that it was designed to find answers to a different problem than yours, you will likely find gaps in answers to your problem. The connection between the specific purpose that originates the research is what differentiate secondary research from primary research.
ocabulary learning is a very important task of second language learners- maybe the most important one. As McLaughlin points out, vocabulary development is the “prime task of adult L2 learners” (1978:324). This is why adults carry dictionaries, not grammars, when they travel in foreign countries (Hatch 1978, cited by McLaughlin 1978). One can keep the communication going provided one knows the content words needed.
The existence of “foreigner talk” and “baby talk”, in which a lot of grammar features (not the content words) are simplified (Ferguson 1971), shows the importance of vocabulary from a different angle. Scientific investigation of learning the foreign language vocabulary, the building blocks of communication, has been largely neglected in the favor of research in other areas of language acquisition in the first three decades of the second half of the century. Holley (1973) observes the role of vocabulary learning in foreign language education, which is held to be secondary. That is because of the first language acquisition research findings, which have misled the teachers. In fact, in first language acquisition, children start acquiring with a small range of vocabulary until structural patterns are mastered; so by relying on these findings, the role of vocabulary is pushed into the background (Carter & McCarthy 1988).
According to Eeds and Cockrum (1985) while there exists a wide variety of ways to deal with vocabulary, the use of dictionary as the conventional method of instruction, in both first and second language learning, has been triggered. Marckwardt (1973), for example, comments: Dictionaries often supply information about the language not found elsewhere. Dictionaries often supply information about grammar, usage, status, synonym discrimination, application of derivative affixes, and distinctions between spoken and written English not generally treated in textbooks, even in a rudimentary fashion (cited in Bensoussan, Sim & Weiss, 1984: 263). Laufer (1990), similarly, believes that when word looks familiar but the sentence in which it is found or its wider context makes no sense at all, the learner should be encouraged to consult a dictionary (p.154)
