That's a fantastic question, and a worthwhile research topic in itself! You're right in your concerns, and indeed there's been an extensive discussion in the li

That's a fantastic question, and a worthwhile research topic in itself! You're right in your concerns, and indeed there's been an extensive discussion in the literature about how valid browser-based experiments are for basic research in psych. If you're interested, the authors of jsPsych have compared native experimental software to their JS-based one (https://dx.doi.org/10.3758/s13428-015-0567-2 https://dx.doi.org/10.3758/s13428-015-0567-2), and our lab has also done some comparisons (https://dx.doi.org/10.3758/s13428-015-0678-9 https://dx.doi.org/10.3758/s13428-015-0678-9). There's a fair amount of literature around this very topic now. In a nutshell, while there's definitely some latency and jitter involved, it's usually far smaller than human response time variability, and averaging across many trials, as well as analysis that takes into account stimulus variability, helps massively to remove noise from the analysis. Also, in many cases, we're interested in difference between times across several experimental conditions/scenarios rather than an exact absolute measurements. Thus, for many applications, browsers are usually accurate enough, and the ease of collecting more data outways the noise. In the end, the only way to deal with latencies properly is to measure and correct for them by calibrating the entire setup. That's what we've done for the new software we're building, which also takes into account render latencies and introduces some more tricks (see https://psyarxiv.com/fqr49 https://psyarxiv.com/fqr49) Hope that helps, would love to chat about this in detail if you're interested!