What is this type of plot called with side-by-side centered horizontal density bars? What would you call this type of plot, and is it possible to create them in R?
EDIT: many thanks all - very helpful.

 A: It's a little hard to tell what the plots are supposed to represent, but they look an awful lot like violin plots.
A violin plot is essentially a vertical, doubled kernel density plot, so that the width along the x axis corresponds to greater density at the corresponding value along the y axis.
You can generate them in package lattice with panel.violin, or in ggplot2 with geom_violin.
Edit: there is also an R package called vioplot that (I think) uses only base R graphics, and a package called beanplot that generates something similar called a "bean plot."
A: Sorry I don't have enough street cred on CV to post a comment, where this is more appropriate, but here is a link to some code in R to perform something like what you've depicted, using base graphics to rotate histograms in place of the density function inherent in ggplot2:
from stack overflow: 
https://stackoverflow.com/questions/15846873/symmetrical-violin-plot-like-histogram
if someone with appropriate powers cares to move this from answer to comment, please do.
