explain personalization effects. While the method opens up the possibility to discover new aspects to the research question, it can make it difficult to investigate subject-specific details and information. To obtain more detailed information about the partic-ipants’ opinions of different language styles, this method should be combined with semi-structured oral interviews.
Another methodical implication is the learning period. In con-trast to previous studies with short time treatments (e.g. Mayer et al., 2004; Moreno & Mayer, 2004), learners in the present study worked with the learning material, on average, for 25–30 min (self-paced instruction). The length of instruction can moderate the learning outcome (Ginns et al., 2013). Therefore, the personaliza-tion principle should be tested in various courses for a different period to explore if there are long-term effects of personalized learning materials on motivation and learning outcomes (e.g. on-line courses during a full semester).
In the present study, a modest change in the wording of the les-son was used to personalize formal texts, for example changing ‘the’ to ‘your’ and ‘one’ to ‘you’ and including few direct comments to the learners. Based on the empirical findings, even modest changes create personalization effects. This leads to the interesting question of whether a higher level of personalization would