Cross your fingers. No, no not that much, Just a little bit like this
(pic) so your finger tips are next to each other.
Now run the tips of your fingers along to top of your teeth. It will feel as though you have two sets of teeth, one inside the other.
Hold a finger out in front of your face. Now take your other hand, extend the index finger and hold it over your head. Try bringing the finger forward to touch the one in front of your face.
Do this as quickly as you can. Try with one eye closed, you may find this difficult as you lose some depth perception by shutting one eye.
Can you do it with both eyes closed?
You should be able to. You know where your finger is without looking at it, as we have sense of self-awareness known as proprioception. This is very useful since it means we are less likely to bump into stuff, or lose a limb.
Sometimes people lose this sense and become unaware of the existence of parts of their own body! In his book “a leg to stand on” the wonderful Oliver Sacks describes such a case, where a man throws himself out of bed after waking and finding a limb, he didn’t think belonged to him.