  The research field of augmented reality (AR) is of increasing popularity, as
seen, among others, in several recently published surveys. To produce further
advancements in AR, it is not only necessary to create new systems or
applications, but also to evaluate them. One important aspect in regards to the
evaluation is the general understanding of how users experience a given AR
application, which can also be seen by the increased number of papers focusing
on this topic that were published in the last years. With the steadily growing
understanding and development of AR in general, it is only a matter of time
until AR devices make the leap into the consumer market where such an in-depth
user understanding is even more essential. Thus, a better understanding of
factors that could influence the design and results of user experience studies
can help us to make them more robust and dependable in the future.
  In this position paper, we describe three challenges which researchers face
while designing and conducting AR users studies. We encountered these
challenges in our past and current research, including papers that focus on
perceptual studies of visualizations, interaction studies, and studies
exploring the use of AR applications and their design spaces.
