After showing two groups of schoolteachers a videotape of an eight-year-old boy, psychologists John Santrock and Russel Tracy found that the teachers’ judgment of the child ultimately depended on whether they had been told the child came from a divorced home or an intact home. The child was rated as less well-adjusted if the teachers thought he came from a home where the parents were divorced. This finding might seem inconsequential to the field of architecture, but for a profession that often relies on observational studies to evaluate a design’s effect on its users I argue that Santrock and Tracy’s study is one among many architects need to pay attention to. An observational study*, like post-occupancy surveys, is a common method architects use to evaluate a design’s effect on its users. If done well observational studies can provide a wealth of valuable and reliable information. They do, however, have their pitfalls, most notably controlling for cognitive and selection biases. At the risk of limiting readership, I will illustrate these challenges by reviewing a specific observational study dealing with autism design. Although specific, the following example wrestles with the same difficulties that other observational studies in architecture wrestle with.