Basil Leaves Turning Upside-Down!

I have three plants of one of the globe basil varieties. One of them I pruned because it spent a night outside... too cold. It is looking nice now, but although the other ones are extremely dense and are growing fine, the leaves have a tendency to turn completely upside-down towards the light. Why would that be? I hope it's fine, I really don't mind that it's that way, I just would like to know if it is my fault, or just a characteristic of this amazing bush! It's sooo > thick!

This is probably a result of where the pot is sitting. Because the bush is dense, the direction of the most intense light for some of the leaves might be what is reflected from the windowsill. Since that would be below the leaves, they would twist to receive it as much as possible. Once they have matured in this position, they won't change later.