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 correlates positions within the textual content to corresponding positions within the 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 the audio content; and a processor in communication with the one or more data stores, the input device and the output device, the processor configured to: cause output of the audio content via the output device; determine an output position for the textual content corresponding to a current output position of the audio content based at least in part on the content synchronization information; cause presentation of a portion of the textual content corresponding to the output position on the display device; during output of the audio content via the output device: determine, based at least in part on the synchronization information, an updated output position for the textual content corresponding to the current output position of the audio content output via the output device, wherein the current output position of the audio content advances during output of the audio content; cause presentation on the display device of an updated portion of the textual content corresponding to the updated output position; obtain the input value from the input device corresponding to performance of the user at the 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, wherein the threshold value is associated with a predetermined playback speed; 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 to correlate to the predetermined playback speed associated with the threshold value; and a speed of presentation on the display device of additional portions of the textual content.