In comparison, I recollect patients at a UK secure hospital being able to memorise keys at a single glance and reproduce them from memory - my colleagues had to

In comparison, I recollect patients at a UK secure hospital being able to memorise keys at a single glance and reproduce them from memory - my colleagues had to keep their keys in leather sheaths at all times. Also - https://www.schneier.com/blog/archives/2005/09/shoulder_surfin.html https://www.schneier.com/blog/archives/2005/09/shoulder_surf...