Example methods and systems for computing a reaction time from an indexed event occurring in an indexed recording to a reaction signal are described. An example method includes receiving a sample of ambient content of a computing device, determining a position identification of the sample of ambient content into an indexed recording to which the sample of ambient content matches, based on the position identification, synchronizing display of content on a user interface of the computing device to the indexed recording, and computing the reaction time. The reaction signal is generated by the computing device and is indicative of a user's response to the indexed event.