The validation of online webcam-based eye-tracking: The replication of the cascade effect, the novelty preference, and the visual world paradigm


The many benefits of online research and the recent emergence of open-source eye-tracking libraries have sparked the interest in transferring time-consuming and expensive eye-tracking studies from lab to web. In the current study, we validate online webcam-based eye-tracking by replicating three robust eye-tracking studies (the cascade effect, n = 134, thenovelty preference, n = 45, and the visual world paradigm, n = 32) online using theparticipant’s webcam as eye-tracker with the WebGazer.js library. We successfully replicatedall three effects, although the effect sizes of all three studies shrank by 20 to 27%. The visualworld paradigm was not only conducted online but also in the lab, using the same participantsand a standard laboratory eye-tracker. This showed that replication per se could not fullyaccount for the effect size shrinkage, but that the shrinkage is also due to the use of onlinewebcam-based eye-tracking, which is noisier. In conclusion, we argue that eye-trackingstudies with relatively large effects that do not require extremely high precision (e.g., studieswith 4 or fewer large regions of interest) can be done online using the participant’s webcam.We also make recommendations for how the quality of online webcam-based eye-trackingcould be improved.

Under review, Preprint