SAN FRANCISCO — Google is sifting through the photos and commentary on its blossoming social network so its Internet search results can include more personal information.

The additional personal touches that began to roll out Tuesday mark another step toward one of Google's most ambitious goals. The Internet search leader eventually hopes to know enough about each of its users so it can tailor its results to fit the unique interests of each person looking for something.

Different people should start seeing different search results more frequently now that Google Inc. is importing content from its 6-month-old Plus service, a product that the company introduced in an attempt to counter the popularity of Facebook's online hangout and Twitter's short-messaging hub. Google's main search results page also will start highlighting more content from an older online photo service called Picasa.

Facebook and Twitter pose a threat to Google because they don't allow Google's search engine to log the avalanche of photos, links and observations tumbling through those services. That's troublesome to Google because its search engine could become less useful if its system can't analyze what people are signaling is important to them so those preferences can be factoring into the results.

Google is tackling that challenge with an addition to its results called "Search, plus Your World."

The feature will be automatically turned on beginning Tuesday for all English-language searches made by users logged into Google. Turning off the personal results permanently will require changing a setting in Google's personal preferences. The personal results can also be excluded on a search-by-search basis by clicking on an icon of the globe on the results page (the personal results will be denoted by a button featuring a human's silhouette).

If the new formula works as Google expects, the search results will include pertinent information culled from the requestor's Plus account. For instance, a query about the San Francisco 49ers might include links and comments made about the football team by other people in one of the social circles on the user's Plus account. A search request that includes the name of a dog owned by the user or a friend might turn up photos of the pet that have been posted on Plus and Picasa.

"This is going to open up a whole new avenue in search," said Ben Gomes, a Google fellow.

Google isn't the first to do this. Microsoft Corp.'s Bing search engine has been mining some of the preferences and other information shared on Facebook since May. But Google's emphasis on more personal results figures to attract more attention because its search engine is so dominant. It handles about two-thirds of the Internet search requests made in the U.S. while Bing processes less than one-third, including the activity that it comes through a partnership with Yahoo Inc.

Facebook, though, has greater insights into personal tastes. That's because its nearly 8-year-old social network boasts more than 800 million users who share more than 1.5 billion photos alone each week. In October, Google said Plus had more than 40 million users. Google hasn't updated the information since then, although some external studies have estimated Plus began the new year with 60 million to 70 million users.

Some of Google's changes may help prod more people into joining Plus.

As part of Tuesday's expansion, the profile pictures of Plus accountholders will appear in the drop-down suggestions on Google's search box. So when typing in "Mary," you may see those named Mary in your circle along with those Google believes you'd find interesting.

In another twist, searches on general topics such as "music" and "sports," will generate suggestions on people, companies and places that have Plus accounts.

While Google is hoping the addition of more personal results will make its search engine even more useful, the changes also could spook some people as they realize how much information is being compiled about them. Google tried to minimize privacy concerns by recently switching to technology that encrypts all its search results to protect the information from slipping out.

Previous privacy missteps by both Google and Facebook resulted in both companies entering into settlements with the U.S. Federal Trade Commission. The FTC agreements require Google and Facebook to submit to external audits of their privacy practices every other year.