7.5 further research
    the results obtained in this study suggest that the approach used deserves further research.
    (a) will more than three times of listening lead to better listening comprehension and incidental vocabulary acquisition? if yes, will there be a threshold of listening times for the success of efl learners' listening comprehension and incidental vocabulary acquisition?
    (b) will longer training of the metacognitive strategies result in a clearer pattern of relationship between efl learners' metacognitive awareness, listening comprehension, and incidental vocabulary acquisition?
    (c) will the training of other strategies (such as directed attention and person knowledge, etc.) reveal relationships between efl learners' metacognitive awareness, listening comprehension, and incidental vocabulary acquisition? if yes, which strategy training will be most helpful for efl learners to achieve listening comprehension and incidental vocabulary acquisition?
    (d) what effect does the learners' l2 proficiency have on their ability to acquire words incidentally through listening comprehension? for instance, will efl learners of higher language proficiency be better in acquiring receptive and productive knowledge of new words?