Especially when papers before it have established that at most only a few photons were needed for perception. The very first line is: "Landmark experiments by

Especially when papers before it have established that at most only a few photons were needed for perception. The very first line is: "Landmark experiments by Hecht and colleagues in the 1940s established that dark-adapted human subjects are capable of reporting light signals as low as a few photons (~5–7)." Looking around, http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.1979.sp012716/abstract?cited-by=yes&288/1/613 http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.1979.sp0... is a 1979 paper showing that a toad retina can respond to a single photon. The claim from this new paper doesn't seem that extraordinary given what's been known for decades.