Craig, S. D., Gholson, B. et al. (2002). Animated pedagogical agents in multimedia educational environments: Effects of agent properties, picture features, and redundancy. Journal of Educational Psychology, 94(2), 428-434.

Two experiments explored the integration of animated agents into multimedia environments in the context of R. E. Mayer's (2001) cognitive theory of multimedia learning. Experiment 1 was a 3 (agent properties: agent only, agent with gesture, no agent) X 3 (picture features: static picture, sudden onset, animation) design. Agent properties produced no significant effects. Both sudden onset and animation conditions facilitated performance relative to the static-picture condition. In Experiment 2, we explored the effects of printed text, spoken narration, and spoken narration with the printed text, in a multimedia environment that included an agent, to investigate effects of redundancy. The spoken-narration-only condition outperformed the other 2,with no differences between printed text and printed text with spoken narration.