Does thinking burn calories If so how many?

Not very many, because it is the body's natural job...

You'd be surprised how much energy the human brain consumes.

Overall its 20% of the energy used by a human body. Scientific minds vastly superior to mine consider that the human brain burns 20 joules per second.

A Kilo-calorie = Calorie = 4184 Joules.

So a human brain uses a Calorie of energy every 3.5 minutes or so.

Consider that next time you are slimming, do less press ups and more maths!