People deeply understand the physics of tinfoil hats. A properly constructed tinfoil hat needs two layers, with the shiny sides facing in opposite directions. Only the shiny side reflects brain waves. You need to reflect in both directions: one direction keeps the government from using waves to put ideas in your head; the other is to keep the government from reading your mind.

The study [0] linked at the bottom of the article has good insights on that, plus it's a marvelous read all around.

[0] https://web.archive.org/web/20060612212953/http://people.csa...

Aren't they from somewhat below waist level a parte posteriori?