Ge effect on perception of English /r/ and /l/ for native Japansese speakers.

A dissertation on the topic Age effect on perception of English /r/ and /l/ for native Japansese speakers.
The paper should study the perception of American English /r/ and /l/ by native Japanese learners of English, and how age and the degree of exposure to english effects the perception of /r/ and /l/.
The paper should be based on the idea of David Birdsongs Critical Period Hypothesis and how this relates to the acquisition of the phoneme /r/ and /l/.
It should have topics such as…
a)why is it so hard for japanese speakers to identify the phoneme /r/ and /l/.
b)what is the critical hypothesis period?
c)is there a difference in the perception of /r/ and /l/, when the japanese learner starts acquiring after the critical period, or before the ciritcal period.
d)the difference of the pronounciation of japanese phoneme /r/ and the english phoneme /r/ and /l/.
e)along with age, does the exposure to english (ex. learning english in schools in japan, or actually living in america) effect on the perception of /r/ and /l/.
f)other aditional topics.

The main source should be…

1)Naoyuki Takagi, Perception of American English /r/ and /l/ by adult Japanese learners of English: A unified view, University of California, 1993.

Other preferred sources are…

1)Katsura Aoyama, Percieved phonetic dissimilarity and L2 speech learning: the case of Japanese /r/ and English /l/ and /r/, Journal of Phonetics, 2004.

2)Reiko A. Yamada, Age effect on acquisition of non-native phonemes, perception of English /r/ and /l/ for native speakers of Japanese, Theoretical and Methodological Issues, 1995.

3)David Singleton, The age factor in second language acquisition, Multilingual Matters, 1995.

4) David Birdsong, Second language acquisition and the critical period hypothesis, Erlbaum, 1999.