Format
A data frame with 22 observations on the following 2 variables.
- proficiency
- a numeric vector
- greymatter
- a numeric vector
Source
Mechelli, A., J.T. Crinion, U. Noppeney, J. O'Doherty, J. Ashburner,
R.S. Frackowiak, and C.J. Price. 2004. Structural plasticity in the
bilingual brain. Nature 431: 757.