Interactive Learning Environments, 20:5, 423-439 (2012)

Main point:

Multimedia instructional materials have to be enriched with support devices in order to be effective. There are two approaches: inserting the support into material (canned  support) or using human tutoring. An experiment was conducted (n=84 into 3 conditions: human aid, canned support, no support) and it showed that human tutoring was better.

From the literature overview: one can experience a human-human interaction with computer.

Further reading – Ginns, P. (2005). Meta-analysis of the modality effect. Learning and instruction, 15