Initial success in biologically extending human vision into the near infrared
experiment.com
experiment.com
It's also very difficult to make a fair comparison. The room must be the same, the light sources must be the same (a new coffeepot with a small led can ruin the experiment, removing a coffeepot because it has recently broken can ruin the experiment).
For a preliminary experiment, the before-after comparison is enough. For a serious experiment you need many voluntaries, compare the before-after signals of them all at the same time in the same experimental conditions, and double blind testing.
There is a small possibility that they are measuring "excitement" instead of light. The subject hears that they are now going to test with very near infrared light. He got exited. They measure that. Perhaps the flash makes a slight sound, perhaps the light operator makes a slight sound. (Perhaps the 850nm flash makes a sound that the other flashes don't make?)
Fascinating project. I absolutely love what the democratization of experimental science is making possible.