Abstract

It has long been known that scientists have a tendency to conduct experiments in a way that brings about the expected outcome. Here, we provide the first direct demonstration of this type of experimenter bias in experimental philosophy. Opposed to previously discovered types of experimenter bias mediated by face-to-face interactions between experimenters and participants, here we show that experimenters also have a tendency to create stimuli in a way that brings about expected outcomes. We randomly assigned undergraduate experimenters to receive two different hypotheses about folk intuitions of consciousness, and then asked them to design experiments based on their hypothesis. Specifically, experimenters generated sentences ascribing intentional and phenomenal mental states to groups, which were later rated by online participants for naturalness. We found a significant interaction between experimenter hypothesis and participant ratings indicating a general tendency for experimenters to obtain the result that they expected. These results indicate that experimenter bias is a real problem in experimental philosophy since the methods and design employed here mirror the predominant survey methods of the field as a whole. The bearing of the current results on Knobe and Prinz’s :67–83, 2008) group mind hypothesis is discussed, and new methods for avoiding experimenter bias are proposed.