# Who invented the independence notation $\perp \!\!\! \perp$?

This is more of a historical question: who invented the notation $$\perp \!\!\! \perp$$ for denoting (conditional) independence?

• To whom it may concern, this question seems to be on-topic. We have many questions on (history of) notation in probability & statistics, and a tag for them notation. – Tim Dec 6 '18 at 8:07
• So the tiny orthogonal vectors ⊥ mean marginal independence and with two vertical lines it's conditional independence? – suckrates Dec 6 '18 at 8:15

• In the 'handbook of graphical models' by Maathuis ea it is written explicitly by Milan Studeny "The author of this chapter was told that the conditional independence symbol $\perp \!\!\! \perp$ was proposed by Dawid and Mouchart in their discussion in the late 1970s" – Sextus Empiricus Dec 12 '18 at 11:32