Take a look at these two images.
Move back and forth between the two.
Now what did you look at on the left and on the right ?
I am pretty certain you would have looked at the front of the lorry on the left and the red van or green van on the right.
Was I correct?
We are born constantly looking for threats. Anything coming towards us is a potential threat. We instinctively look at the lorry and see it is not a threat and move on. Now, I grant you that the vehicle positions have changed slightly in the right image, but you ignore the lorry and look at the vans.
xxxxTry experimenting with this idea on your own layout. If you put a vehicle coming towards you I guarantee you will look at it and then move on. Turn the same vehicle around and you will initially ignore it.
Les Scanlon, from whom I learnt about the black base technique, was a psychiatric nurse. He had all sorts of interesting insights into how our minds work and this is just one of them.