RESUMEN
This manuscript introduces BITTSy, the Behavioral Infant & Toddler Testing System. This software system is capable of running the headturn preference procedure, preferential looking, conditioned headturn, and visual fixation/habituation procedures. It uses only commercial-off-theshelf (COTS) hardware to implement the procedures in an affordable and space-efficient setup. The software package, example protocols and data sets, and manual are freely available and downloadable from go.umd.edu/BITTSy, making this entire set of procedures available to resource-limited labs. Researchers can easily use BITTSy at multiple sites in a uniform manner, resulting in a standardized, powerful research tool that can enhance cross-site research collaborations.