Visual DMDX: A web-based authoring tool for DMDX, a Windows display program with millisecond accuracy.

DMDX is a software package for the experimental control and timing of stimulus display for Microsoft Windows systems. DMDX is reliable, flexible, millisecond accurate, and can be downloaded free of charge; therefore it has become very popular among experimental researchers. However, setting up a DMDX-based experiment is burdensome because of its command-based interface. Further, DMDX relies on RTF files in which parts of the stimuli, design, and procedure of an experiment are defined in a complicated (DMASTR-compatible) syntax. Other experiment software, such as E-Prime, Psychopy, and WEXTOR, became successful as a result of integrated visual authoring tools. Such an intuitive interface was lacking for DMDX. We therefore created and present here Visual DMDX (http://visualdmdx.com/), a HTML5-based web interface to set up experiments and export them to DMDX item files format in RTF. Visual DMDX offers most of the features available from the rich DMDX/DMASTR syntax, and it is a useful tool to support researchers who are new to DMDX. Both old and modern versions of DMDX syntax are supported. Further, with Visual DMDX, we go beyond DMDX by having added export to JSON (a versatile web format), easy backup, and a preview option for experiments. In two examples, one experiment each on lexical decision making and affective priming, we explain in a step-by-step fashion how to create experiments using Visual DMDX. We release Visual DMDX under an open-source license to foster collaboration in its continuous improvement.