It is my opinion that there are too many variables for us to determine if the flash spooks the deer. Maybe someone with penned deer could do a test but it would be difficult since the tameness of the deer could bias the results.

I've watched deer get flash pictures taken and none of them ran. I also have thousands of pictures of deer taken with a flash and most of them are not looking at the flash. I think that many of the deer that are looking at the camera when the picture is taken are looking at the camera because they hear the camera's shutter open up. If they look at the camera when it flashes then it would be too late. Once the flash goes off the deer has already had its picture taken. Surely a deer cannot beat the speed of light and turn it's head.

Once again this is my opinion from my experiences. I've not yet seen any study that would prove otherwise. For instance you would even have to be sure that the flash and IR camera have the same dependability. I've used 19 different cameras and the dependability varies widely. I've also had deer show up for a couple of weeks and then be no shows for a week or so and then show up again. These critters are very hard to pin down.