Here is a nice master’s thesis by Chantal Mülders called ‘Can I Learn How to Sign: Exploring aptitude for spoken language and visual stimuli in connection with sign language’. (Master of Arts, Radboud University Nijmegen, 2007). Usually these theses aren’t published but since there is so little published on Sign Language of the Netherlands (SLN) I offered her to publish it here.
Summary: This thesis explores the relationship between linguistic and visual aptitude and sign language learning to see what abilities are necessary for sign language acquisition and whether these differ from spoken language acquisition. 29 Students enrolled in a Sign Language minor took four tests before the start of their practical sign language course: a Sound Discrimination test, a Sign Language test, a Shape Discrimination test and a Visual Spatial Discrimination test. The Sign Language test was constructed for this thesis and focused on phonological and phonetic alterations of handshape. The other tests originated from aptitude test batteries. After seven weeks of sign language instruction, the students took a proficiency test that tested their receptive and productive sign language skills. This proficiency test was constructed by the sign language teacher and was the student’s final exam for the course. 18 Students remained who had taken all five tests. Correlations between the four tests and the proficiency test show that the Sign Language test has a decent, but insignificant correlation with Reception. The Sound Discrimination test did not show a relationship and the Shape Discrimination test had a steady, but low and insignificant relationship. The Visual Spatial Discrimination test correlated negatively with Reception. This was the only significant correlation between the four tests and the proficiency test. It is likely that the subject group was not varied enough and all subjects performed above a certain critical level.
I conclude that sign language learning appears to require different abilities from spoken language acquisition, but the current subject group is too small for a definite answer.