Tuesday, December 08, 2009

Personalized search for all at Google

As has been widely reported, Google is now personalizing web search results for everyone who uses Google, whether logged in or not.

Danny Sullivan at Search Engine Land has particularly good coverage. An excerpt:
Beginning today, Google will now personalize the search results of anyone who uses its search engine, regardless of whether they've opted-in to a previously existing personalization feature.

The short story is this. By watching what you click on in search results, Google can learn that you favor particular sites. For example, if you often search and click on links from Amazon that appear in Google's results, over time, Google learns that you really like Amazon. In reaction, it gives Amazon a ranking boost. That means you start seeing more Amazon listings, perhaps for searches where Amazon wasn't showing up before.

Searchers will have the ability to opt-out completely, and there are various protections designed to safeguard privacy. However, being opt-out rather than opt-in will likely raise some concerns.
There now appears to be a big push at Google for individualized targeting and personalization in search, advertising, and news. Google now appears to be going full throttle on personalization, choosing it as the way forward to improve relevance and usefulness.

With only one generic relevance rank, Google has been finding it is increasingly difficult to improve search quality because not everyone agrees on how relevant a particular page is to a particular search. At some point, to get further improvements, Google has to customize relevance to each person's definition of relevance. When you do that, you have personalized search.

For more on recent moves to personalize news and advertising at Google, please see my posts, "Google CEO on personalized news" and "Google AdWords now personalized".

Update: Two hours later, Danny Sullivan writes a second post, "Google's Personalized Results: The 'New Normal' That Deserves Extraordinary Attention", that also is well worth reading.


jeremy said...

At some point, to get further improvements, Google has to customize relevance to each person's definition of relevance. When you do that, you have personalized search.

Also, when you allow an individual to explicitly say what is and isn't relevant to them, does that also mean you have personalized search? Or is search only personalized when there is an implicit, inference-laden interaction?

Greg Linden said...

Hi, Jeremy. I'd say that's the difference between implicit and explicit personalization. Both are types of personalization, I'd think.

It's a little hard to know where to draw the line, but I wouldn't call faceted search personalization. It doesn't use history other than keeping previous state for building up a complex search query, so I wouldn't label that personalization.

Why, what do you think?

Fran├žois Schiettecatte said...

I would suggest that personalization happens when the search results are modified from their generic form to suit the needs of the user looking at them, whether this modification is done automatically by the system (from information gathered over time), or explicitly when the user indicates what is and what is not relevant to them.

jeremy said...

I think that when most people say personalized search, they mean implicit personalized search. That's the common parlance.

I just don't see what the difference is, from a back-end, technical standpoint, between implicit and explicit. Well, other than what I've heard about search engines treating personalization more like group personalization, i.e. lumping you in automatically with similar-clicking and similar-querying people, so as to overcome the sparsity/cold start problem.

So is that it? Is that the difference? In (implicit) personalization, it's more group-personal than it is perfectly-tailored-personal?

Explicit personalization is perfect tailoring.