In an online experiment the procedure runs in the participant’s own browser, without an experimenter present. The researcher cannot see whether instructions were read, whether a video used for a mood induction was watched, or on which device and screen the stimuli appeared.
This line of research builds open infrastructure for running such experiments and tests how adherence to the procedure can be checked. Open Lab runs experiments built with lab.js as managed online studies, with study scripts open to inspection and reuse. An earlier study showed how participants who skip a film-clip mood induction can be detected and how their data can be handled in the analysis.
Current work extends this to online studies in which some participants may be automated agents instead of people.
Five trials of a simple reaction-time task. Each trial waits a random 1 to 3 seconds before the circle changes colour, so the onset cannot be anticipated. Browser experiments record stimulus onset and response with the same JavaScript timing functions used here.
Part of the measured time comes from the screen and the input device, and this part differs between devices. Nothing is stored or sent.
On timing accuracy across experiment software and browsers: Bridges, D., Pitiot, A., MacAskill, M. R., & Peirce, J. W. (2020). The timing mega-study: Comparing a range of experiment generators, both lab-based and online. PeerJ, 8, e9414. https://doi.org/10.7717/peerj.9414
Tap the panel or press space when the circle turns amber.
Runs experiments built with lab.js as managed online studies, with hosting, participant management and data export, so researchers need no server of their own. As of August 2026, 308 researchers had run 291 studies with 15,355 participant enrolments.
A free, open online study builder by Felix Henninger and colleagues. Open Lab runs the experiments built with it.
* Open Lab and SMAAT are operated by Open Lab Online UG (haftungsbeschränkt). Yury Shevchenko develops both platforms, which are available for research use with free and paid tiers, and may benefit financially from their institutional use.