Researcher claims "not enough science" in learning-styles studies

http://www.npr.org/blogs/health/2011/08/29/139973743/think-youre-an-auditory-or-visual-learner-scientists-say-its-unlikely

Anyone see this on NPR?  I'd like to know why Dr. Willingham considers previous qualitative research into learning styles as inconclusive.  The NPR article doesn't give any real details and the link to http://www.psychologicalscience.org , where his analysis is published, is overloaded and won't load.