Pair programming should **not** be used to train inexperienced or less-skilled developers.

[Studies and meta-studies][1] that support pair programming on a general, conceptual level, almost invariably find that the gains in quality and productivity only outweigh the added cost when both programmers are at roughly the same skill level.

In fact, this has pretty much become a "rule" in academic settings. Universities which recommend the practice also [state explicitly that students should find a partner with the same skill level][2]. Not better, not worse - the same.

Note that "skill level" here is domain- and task-specific. Pairing a brilliant UI developer with a brilliant algorithm designer or database developer is no better than pairing a brilliant UI developer with a totally green UI developer.

The studies (corroborated by my own personal experience) show that inexperienced developers (in some area) learn faster when paired, and highly-skilled developers can catch serious misunderstandings and design problems much earlier, negating much of the time spent on debugging and rework.

However, there is a gradient of almost 10x the productivity for the least vs. most skilled developers. Pairing someone highly-skilled with someone very green is very much like pairing a driving instructor with a student. You don't have real co-operation, you have a driver and a passenger, a master and an apprentice. If the apprentice "drives" then the master is too busy monitoring and correcting errors to get any work of his own done. On the other hand, if the master "drives" and the apprentice is told to watch and learn, the master is less productive due to the interruptions and the apprentice does not learn very effectively.

This is a no-win situation. If new developers need to be trained, then call a spade a spade and *train* them. Or apprentice them, have them "shadow" a more experienced developer for a while. But don't call it "pair programming" and expect to get good results. Those only occur when both partners have similar skill sets.

  [1]: http://dl.acm.org/citation.cfm?id=1309094
  [2]: http://ic.ucsc.edu/~ptantalo/cmps5P/Spring13/pair-programming.html