1. A system for synchronizing output of audio content with textual content, the system comprising: one or more data stores that store textual content, audio content, and content synchronization information, wherein the content synchronization information comprises information for synchronizing textual content and audio content; an input device that obtains an input value corresponding to performance of a user at a task; a display device that presents the textual content; an output device that outputs audio content; and a processor in communication with the one or more data stores, the input device and the output device, the processor operative to: cause output of the audio content via the output device; cause presentation of the textual content on the display device; maintain, based at least in part on the synchronization information, synchronization of a position of the textual content presented on the display device with an associated position of the audio content output via the output device, wherein the associated position of the audio content advances during output of the audio content; obtain an input value from the input device corresponding to performance of a user at a task; determine that the user's performance at the task has dropped below a threshold value based at least in part on the input value from the input device; and responsive to the determination that the user's performance at the task has satisfied the threshold value, modify a speed at which the audio content is output via the output device.