Say, for example, we have a table with various rows, and you can check a checkbox to select the row. Is it more natural to have the checkbox on the leftmost column, or the rightmost column?
Leftmost column for left-to-right readers and vice-versa.
Left-to-right readers will see the checkbox at the very beginning of scanning the row. So they will start scanning knowing that there is a possibility that cells can be selected in bulk (or at least their subconscious knows since it has registered the checkbox). Later on, if there is a need to select the whole row at once (and not just one cell), they know where to find the checkbox to do that and they don't need to scan the whole row to see if there is a checkbox, as rows can be of any length.