Cognitive overload and OPTIONAL content
I'm working my way through E-Learning and the Science of Instruction by Clark and Mayer. The section I'm reading now discusses the coherence principal, which is basically KISS. Any information that doesn't directly contribute to the learning objectives should be removed because it doesn't increase the learner's retention rate and in many cases impedes retention.
Good stuff, makes sense, I've been saying that for years. It has frequently come up where my SME wants to include a lot of additional information and I've talked them down from that cliff by suggesting that information be offered as optional (meaning, on the website, or accessed through a button or the resources menu, what have you). For example, in one thing I'm working on, there are video testimonials that the learner could view if they wanted, but they are optional.
Anyone familiar with research that goes into whether optional material harms retention? My gut after reading this far into the book says yes, because it would still be taking up short and long term memory for the learner. But the studies have also found that higher-level learners (ie, learners who already have a decent grasp of the material) can easier deal with extra information than lower-level learners, and my guess is that it's primarily the higher-level learners who would access this optional information.