Is it normal that i can split my vision of my two eyes on command?

Is it normal that I can split my vision on command without doing the finger in front and look behind trick? I can look at place on a wall and control my split vision and blur without delay, it creates two images that overlap and are slightly opaque. This can make an weird effect by putting my two thumbs up, doing the split vision and putting two of the four thumbs together to make three. (sorry if I lost you there) Is this normal? I heard that its a genetic mutation which allows you to control the stereoscopic vision of your eye rather than it being automatic. Is this true? When I tell people about it they think im crazy.