## 4 Discussion
### Limitations  
We have to acknowledge a number of limitations of the present study. A first limitation to be mentioned concerns the relatively small sample sizes. This could have limited the power to find differences between the route learning methods. It turned out to be relatively hard to recruit sufficient participants because of COVID-19-related restrictions at the time of the study. Moreover, the training schedule was relatively long for certain individual patients residing in long-term KS care, and they lost the motivation to continue. This is quite typical for patients with KS, as suggested by earlier work showing high levels of apathy in this population [56]. When computing the required sample size for obtaining a medium effect size given the group by training session design, we would have needed at least 42 participants [44]. Hence while the learning effect is clearly established, subtle differences between learning methods could have been masked by the small group sizes. Another reason for not finding any learning method effects could be that differences between learning methods are limited to the initial stages of the training sequence. We can see that in the trial-and-error group, the error rate dropped by approximately 50% when going from the first training to the midterm training session. For the errorless and the passive learning group, the first measurement was made halfway though the training program. This was done to refrain the participants from making errors. In a completely different setup, it could be interesting to compare groups already at the second or third training moment. However, any subsequent learning would then be flawed by the errors made on that occasion. One may question whether the groups were comparable in their route learning ability at baseline. Given the comparable scores on the MoCA--a cognitive screener--it is not very likely that the groups initially would have differed in route learning ability. One way to determine this more precisely is to offer participants a second route that was learned on a single occasion in the passive learning condition and was tested next. This could, however, have caused inter-route interference, especially since both routes would have to start from the same point, the exit of the clinic where the patients resided. A further limitation to be mentioned relates to some of the cognitive tests included in the study. As there is no parallel version of the Stroop Test and the FAB, we used the same test versions in the pre- and post-training measurements. There is the possibility that the improvement in attention functioning we observed may have been influenced by practice effects. [PERSON] et al. [57] showed practice effects on the Stroop task in younger and older participants. However, they used a rather large number of multiple consecutive task blocks with many trials, separated by either no delay (experiment 1) or about a week (experiment 2). In the present study, we had a much shorter task, and the two measurements were separated by at least 6 weeks. We therefore think that practice might have had a minimal influence on the observed training-related attention improvements, if any at all. While no objective learning method differences were observed, we still want to point towards a more qualitative observation. The experimenters casually noticed that the errorless learning participants appeared to have a stronger appreciation of doing the route task than the participants in the other two groups. Actively searching and finding the correct solution (route continuation) and also not being frustrated by mistakes arguably is a much more rewarding experience. The errorless learning condition in this study made the participants actively scan the environment and focus on landmarks. Landmarks form important building blocks for cognitive maps of the environment--perspective-free, allocentric spatial maps [46; 47; 58].