Ask HN: How does a submission's current rank influence voting

taking hn as an example, it seems like there is a fairly simple a/b test you can do that doesn't really harm user experience. swap the order of, say, the 5th and 6th ranked article for some people, and see if there is a noticeable effect on votes, and repeat for all positions on the front page. maybe this has been done here or somewhere else already- im curious what the results were. assuming there is an effect at all, i think its something the ranking algorithm should account for.