Excellent review of an important topic: Working memory capacity.  The limitation in working memory capacity is the most objective, easily measured, and tractable property of conscious thought..
Luck and Vogel (2013)

Miller Lab work cited:
Siegel, M., Warden, M.R., and Miller, E.K. (2009) Phase-dependent neuronal coding of objects in short-term memory. Proceedings of the National Academy of Sciences, 106: 21341-21346. View PDF »

About the Author

The Miller Lab uses experimental and theoretical approaches to study the neural basis of the high-level cognitive functions that underlie complex goal-directed behavior. ekmillerlab.mit.edu