Shops often have lifesize cut-outs standing round to keep an eye on people. The assumption is that people pick up that they are under observation, and are less likely to nick stuff. It seems to have that effect.

In this case there's presumbaly no question of telepathy from a cardboard cut-out, it's a matter of peripheral vision and the fact that, as gnomade said, "we are instinctively scanning our surroundings".