What is the scientific support for Einstein's claim about the negative effects of reading too much? Einstein once said:


  Reading, after a certain age, diverts the mind too much from its
  creative pursuits. Any man who reads too much and uses his own brain
  too little falls into lazy habits of thinking, just as the man who spends too much time in   the theater is tempted to be content with living vicariously instead of living his own life.



What is the scientific claim implicit in this quote?
Is it true that reading too much makes the mind lazy, and is reading too much harmful to the mind?


*Quote from an interview with G.S. Viereck, "What Life Means to Einstein," Saturday Evening Post, October 26, 1929; re-printed in Viereck, Glimpses of the Great, 437.
This answer is a bit more anecdotal, but perhaps it's useful.

From the perspective of an academic researcher (which perhaps is similar to Einstein's perspective), there is a balance between reading the literature and conducting your own research. There is a balance between learning new skills and applying those skills to your own projects. Even within the context of learning, there is a balance between reading how something is done and practicing actually doing it.

The very process of conducting your own research reveals challenges and gaps in understanding. Reading allows you to take on new information, however, doing good research also requires time to re-arrange ideas, refine your own theories. Furthermore, reading can vary in the degree to which it is a passive or active process. As an active process, choosing what to read, critically evaluating reading, is all part of building knowledge and ideas.

These ideas manifest in many places in curriculum design. A PhD thesis in particular is a good example of a project that requires a balance between understanding the existing literature and independent thought.

I presume that the quote is just a useful linguistic device to get people to think about this balancing process.