Best practices: Two Web-browser-based methods for stimulus presentation in behavioral experiments with high-resolution timing requirements.

The Web is a prominent platform for behavioral experiments, for many reasons (relative simplicity, ubiquity, and accessibility, among others). Over the last few years, many behavioral and social scientists have conducted Internet-based experiments using standard web technologies, both in native JavaScript and using research-oriented frameworks. At the same time, vendors of widely used web browsers have been working hard to improve the performance of their software. However, the goals of browser vendors do not always coincide with behavioral researchers' needs. Whereas vendors want high-performance browsers to respond almost instantly and to trade off accuracy for speed, researchers have the opposite trade-off goal, wanting their browser-based experiments to exactly match the experimental design and procedure. In this article, we review and test some of the best practices suggested by web-browser vendors, based on the features provided by new web standards, in order to optimize animations for browser-based behavioral experiments with high-resolution timing requirements. Using specialized hardware, we conducted four studies to determine the accuracy and precision of two different methods. The results using CSS animations in web browsers (Method 1) with GPU acceleration turned off showed biases that depend on the combination of browser and operating system. The results of tests on the latest versions of GPU-accelerated web browsers showed no frame loss in CSS animations. The same happened in many, but not all, of the tests conducted using requestAnimationFrame (Method 2) instead of CSS animations. Unbeknownst to many researchers, vendors of web browsers implement complex technologies that result in reduced quality of timing. Therefore, behavioral researchers interested in timing-dependent procedures should be cautious when developing browser-based experiments and should test the accuracy and precision of the whole experimental setup (web application, web browser, operating system, and hardware).