Do individuals see what they expect to see in a physics experiment?: Revisiting Schlichting’s example of the illumination of a filament

The present study investigates the alignment between individuals’ preconceived naïve conceptions and their actual observations during a physics experiment. Building on Schlichting’s (1991) well-cited but anecdotal example of a classroom experiment, we conducted an online survey involving 158 participants to assess their predictions, reasonings, and subsequent observations of a light bulb filament’s illumination. Our results indicate a high consistency between participants’ predictions and their reasoning but only very weak alignment between these predictions and reasonings and their actual observations. Moreover, logistic regression analyses revealed significant but modest effects of predictions and reasonings on observed outcomes. These findings imply that while naïve conceptions can influence individuals’ observations, the impact is not as predictive as some anecdotal examples within the literature on physics education might suggest.