Abstract
Researchers often make strong claims about real-world phenomena on the basis of their controlled scientific studies, but small choices in experimental design can have large and sometimes unexpected effects on the likelihood that the results do generalise. For instance, in studies of gaze, participants are usually aware of the task for which their eye and head movements will be studied. Since people are often unaware of how they move their eyes and head, it makes sense to assume that knowing what the experiment is about will not make a difference. But is this true? Here, we explored whether knowing what the experiment is about biases gaze towards task-related structures. We examined whether gaze when people are explicitly asked to climb a staircase is different to that when they have to climb the same staircase on their way to perform a different task. We found that participants fixated fewer steps and looked around more when they were not aware that the staircase was relevant for the study. In particular, they made more saccades towards the side of the staircase and fewer saccades from one step to the next. The differences in gaze have clear implications for studies in which the goal is to understand gaze in daily life, where people are usually not directly asked to perform specific actions. Crucially, the findings demonstrate the profound effect that participant expectations can have on experimental findings and on the ability to generalise those findings to make inferences about real-world tasks.