How great is this?  If you are estimating the height of the Eiffel Tower, you will likely offer a slightly smaller estimate if you are leaning just barely to the left.  In fact, your estimations of all types of numbers — height, but also quantities, weights, etc — will generally be smaller if you are leaning just a wee bit left of center.

Here’s the data: variation between average estimates were statistically insignificant if answered when standing upright or leaning to the right (gray and black, respectively), but leaning to the left depressed estimated quantities (white):

Why?

Here’s a hint: we would expect the results to be the converse if we used research subjects who primarily spoke Arabic or Hebrew.

English, in contrast to those two languages, is read from left to right. When we write down numbers in order, then, the numbers on the left are smaller than those on the right.

We learn, over time, to associate smaller numbers with our left side and larger numbers with our right side.  This constant association biases our mind towards smaller or larger numbers, hence the data.  How great is that?