A surveillance camera was used to snap photos of a lecture hall. A computer was also used to help analyze the images by determining the number of empty seats, presumably based on how many seats there are in the hall followed by how many students are enrolled for a particular class. However the system was not able to identify students individually, so we guess this is looking at attendance in general.
Now there is a bit of controversy behind the experiment as the 2,000 or so students who came for classes were not told about it in advance, which also meant that they could not object to have their photos taken/recorded. According to the researchers, they claimed to have followed the right steps by informing the review board in advance and deleting the photos as soon as the experiment was concluded.
However given that there is a bit of fuss surrounding the experiment, Harvard has decided to rethink its strategy by handing the issue over to an oversight committee. Given that Facebook had similarly conducted a secret experiment on its users and faced huge backlash, we guess we can’t say we’re too surprised about it, although at the end of the day it does sound like an interesting way to keep track of how many students attend classes on average.