[1] Through his past work on programming languages such as R and Lisp, Tierney now holds a position on the developing team known as the R Core.
[1] In 1990, Tierney wrote the XLispStat package using C and Lisp[3] and has since published works such as LISP-STAT: An Object-Oriented Environment for Statistical Computing and Dynamic Graphics (Wiley Series in Probability and Statistics) describing its design and use.
[4] Tierney has also made contributions in areas such as reference counting, vectors, and compilation for the R programming language and environment.
[1] During his time working with R, he has also become part of the R Core, a team of developers with write access to the R source.
His work on Markov chains, Bioconductor, Lisp-stat and the Metropolis–Hastings algorithm have all been highly cited.