Proprioceptive alphas are able to take advantage of the human "blind spot".
There is a naturally ocurring 'blind spot' in the human eye that results from the optic nerve passing through the retina. Normally this gap in vision is very small, and is automatically filled in by your brain using information from the area around it. A proprioceptive Alpha can somehow expand the blind spot to accommodate their size, possibly by enlarging the optic nerve so that it blocks a larger space. The name "proprioceptive" comes from the name of the 'sixth sense' that causes people to feel that they are being watched, and refers to the fact that this is the most common sign of their presence.