I'm reading Steve Bragg's excellent book The Accounting Controls Guidebook. In the Control Principles section, he covers expected topics like segregation of duties and management support, but he also spends some time on training as a control principle. Specifically:
"Systems knowledge. It is impossible to expect employees to conscientiously inspect controls unless they already know how systems operate. This calls for the ongoing training of employees to ensure that they thoroughly understand all aspects of the systems with which they are involved. This requires not only an initial training session for new employees, but also reminder sessions...