Monday, June 14, 2010

Google on presentation bias in search

A few Googlers at WWW 2010 had a paper, "Beyond Position Bias: Examining Result Attractiveness as a Source of Presentation Bias in Clickthrough Data" (PDF), that explores how much people tend to click on eye-catching search results rather than seeking the most relevant search results.

The work itself was pretty simple -- just looking at how bolding title and abstract terms changes clickthough rates in A/B tests -- but I think the paper is worth a peek for two reasons. First, it is a decent survey of some of the current work on position and presentation bias. Second, it exposes some of Google's struggles with the difficulty of deriving searcher satisfaction from the noisy proxies that we have available like click data.

By the way, I love the fact, noted in the paper, that people tend to click on the last result much more than you would expect. The reason is that people don't linearly scan down a page, but often jump to the bottom and focus attention there. A decade ago at Amazon, the personalization team exploited this effect and seized the space at the bottom of most pages on the site for our features. You see, when we saw no one had built tools to track click and conversion data, we built them, and then we used them. No one else realized the value of the space at the bottom of the page, but we did.

For more on the struggle to evaluate search results from noisy click data, please see some of my older posts, "Modeling how searchers look at search results ", "Finding task boundaries in search logs", and "Testing rankers by interleaving search results".

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