Timing accuracy of web experiments: A case study using the WebExp software package

Although internet-based experiments are gaining in popularity, most studies rely on directly evaluating participants ’ responses, rather than reaction times. Here we present two experiments which demonstrate the feasibility of collecting response latency data over the world-wide web, using WebExp, a software package designed to run psychological experiments over the internet. Experiment 1 uses WebExp to collect measurements for known time intervals (generated using keyboard repeti-tion). The resulting measurements are found to be accurate across platforms and load conditions. In Experiment 2, we use WebExp to replicate a lab-based self-paced reading study from the psycholinguistic literature. The data of the web-based replication correlate significantly with the data of the original study and show the same main effects and interactions. We conclude that WebExp can be used to obtain reliable reaction time data, at least for the self-paced reading paradigm