Hasler, B. S., Kersten, B., & Sweller, J. (2007). Learner control, cognitive load and instructional animation. [10.1002/acp.1345]. Applied Cognitive Psychology, 21(6), 713-729. 

Learning materials can differ substantially in the extent to which they impose cognitive

load.  Intrinsic CL + Extrinsic CL + Germane Cognitive Load must not exceed the learner's working memory limit.  Instructional effects and design principles that derive from Cognitive Load Theory that were employed in this study include 

the split attention effect

the redundancy effect

the modality effect; and 

the pacing and segmentation effect.

Each of these effects were tested in four controlled experiments (Stop Play, Segments, Narration and Continuous).  The researchers found that the Stop Play group performed better in the high element interactivity questions.  It was also noted by the researchers that these participants were novelists to the Stop Play platform.

Learner control should be integrated into educational animation.  My son, this week, created an animation as the presentation tool.  It was designed so that students could revisit the learning segments at another time; hence learner controlled and cognitive load does not exceed learner's working memory.