User expectations impact the evaluation of new interactive systems. Increased expectations may enhance the perceived effectiveness of interfaces in user studies, similar to a placebo effect observed in medical studies. To showcase the placebo effect, we conducted a user study with 18 participants who performed a target selection reaction time test with two different display refresh rates. Participants saw a stated screen refresh rate before every condition, which corresponded to the true refresh rate only in half of the conditions and was lower or higher in the other half. Results revealed successful priming, as participants believed in superior or inferior performance based on the narrative despite using the opposite refresh rate. Post-experiment questionnaires confirmed participants still held onto the initial narrative. Interestingly, the objective performance remained unchanged between both refresh rates. We discuss how study narratives influence subjective measures and suggest strategies to mitigate placebo effects in user-centered study designs.

翻译：用户期望会影响对新交互系统的评估。在用户研究中，增加的期望可能增强界面的感知有效性，类似于医学研究中观察到的安慰剂效应。为展示这一效应，我们开展了一项包含18名参与者的用户研究，他们在两种不同屏幕刷新率下执行目标选择反应时间测试。每次实验条件前，参与者会看到标明的屏幕刷新率——该数值仅在半数条件下与实际刷新率一致，其余半数则偏高或偏低。结果显示成功启动效应：尽管实际使用的是相反刷新率，参与者仍基于提示语相信自身表现更优或更差。实验后问卷证实参与者仍保持初始提示语的影响。值得注意的是，两种刷新率下的客观表现并无差异。我们讨论了研究提示语如何影响主观测量指标，并提出了在以用户为中心的研究设计中缓解安慰剂效应的策略。