“…However, these differences are rarely acknowledged in the operationalization of redundancy and since studies base their concept of redundancy on either one or both approaches (Austin, 2009; Chandler & Sweller, 1991; Craig et al, 2004), conditions labelled as redundant vary in terms of used sources of information as well as their degree of contentual overlap across studies. For example, redundancy is according to the chosen theoretical approach operationalized in terms of used sources of information as animation + narration + text (Aldalalah & Fong, 2010; Austin, 2009; Diao & Sweller, 2007; Kalyuga et al, 1999), image + text (Chandler & Sweller, 1991) or animation + narration (Lai, 2000). In terms of degree of contentual overlap most studies operationalize redundancy as an contentual overlap between multiple sources of information (DeLeeuw & Mayer, 2008; Sweller & Chandler, 1994).…”