According to a survey of 422 employees, spanning all generations, the #1 "preferred" type of learning and the one deemed "most helpful" is one-on-one mentoring.

The other top vote-getters, in order:

1.       One-on-one mentoring

2.       Traditional classroom learning

3.       Team collaboration

4.       Online courses (they did not specify if this was asynchronous only)

Source: Jones/NCTI survey

You can view the full report, "What Gap? Generational Views on Learning and Technology in the Workplace," here.