True story: I once lived in an area where I could legally bowhunt right out my backdoor. The wooded area was so overpopulated with whitetails that they'd often come right up in my backyard while I was shooting at my 3D target. These were wild whitetails, but they'd learned to live in close proximity to people.
In other words, they'd stand 20 yards away while you walked to refill a bird feeder, but if you stepped back into the woods just a bit they were as wary as any whitetail on the planet. I believe they approached my 3D target because they thought food was available, even though I didn't feed the deer.
As I stood on my deck launching arrows into my target below, I'd often have to wait for a deer to step aside from in front of my target, and sometimes they'd stand within 10 feet of the target as arrows slammed into it. When I retrieved my arrows, the deer would retreat 20 yards and simply stare at me.
Occasionally I conducted an experiment. Because I liked to practice with a quiver attached to my bow back then, I had broadhead-tipped arrows on-hand. In fact, I carried a Judo point in my quiver at all times, too.
When I walked to retrieve my field-tipped arrows from the target, I sometimes reached into my quiver, grabbed the Judo arrow and placed it on the string. The deer simply stared at me and then calmly went back to feeding. If I placed a field-tipped arrow on the string while standing next to the target, the deer continued to remain calm. But if I pulled a broadhead-tipped arrow from my quiver—and this is important—with full intentions on shooting (legally) one of these backyard whitetails, they'd immediately flee to 75 yards and then look back.
Note: After placing the broadhead-tipped arrow on the string, I didn't walk any closer to the deer. I didn't even attempt to draw on them. The only thing that was different was my mindset—and the faster-beating heart a hunter always has when he or she decides to shoot. So unless these backyard deer were born with an understanding of what a field point and Judo point looks like when compared to a broadhead, the only thing I can conclude is the deer could "feel" the very real danger.
Think I'm crazy? Well, it's scientifically accepted that all living things emit an electrical energy field. So what can a hunter do to combat this problem?
Check this out: HECS (Human Energy Concealment System) produces hunting clothing that blocks your electrical energy field, stopping energy signal recognition. Used in an overall clothing system with good camouflage and odor elimination, and assuming you aren't moving too much, too fast or making noise, I believe it's possible that HECS clothing can increase your success in the field.
I haven't had the chance to try HECS yet, but you can bet I will this upcoming deer season. I'll keep you posted.