Célia

Even among humans this varies, I remember that in some countries shaking your head horizontally means yes and vertically means no. This means it is a cultural behaviour in humans, but an innate behavior in dogs. I don’t think it makes sense comparing those two behaviors.

Those don’t work well if you stop moving for extended periods of time, and do not see through bed sheets in my experience

Thank you for your answer :)

This website asks for quite a lot of personal information :/

No they mean their screwmates