Google’s kinship with the mind
Dec 07,2007 00:00 by Bend_Weekly_News_Sources

Think­ing and us­ing an In­ter­net search en­gine might seem to be two very dif­fer­ent ac­ti­vi­ties. But a study sug­gests they draw on si­m­i­lar prin­ci­ples.

When you type words in­to the pop­u­lar Goo­gle search en­gine, it re­turns a list of web­pages con­tain­ing those words. The list is­n’t or­dered any old way: it’s or­dered based on how “im­por­tant” Goo­gle deems the pages to be. Goo­gle meas­ures a page’s “im­por­tance” us­ing a for­mu­la based on pop­u­lar­ity. It takes in­to ac­count how many oth­er pages link to that page; how many oth­ers, in turn, link to those; and so on.

(Courtesy Google Inc.)

Now, psy­chol­o­gists have found that our brains re­turn re­sults in much the same way when giv­en a sim­ple task, such as to think of a list of words that start with A.

Thom­as Grif­fiths of the Un­ivers­ity of Cal­i­for­nia, Ber­k­e­ley, and col­leagues ranked the “im­por­tance” of over 5,000 words us­ing the same basic Goo­gle for­mu­la, called Page­Rank. But in­stead of In­ter­net links, the re­search­ers tal­lied men­tal “links” be­tween words as re­flected in an­swers giv­en in word-associa­t­ion games by peo­ple par­ti­ci­pat­ing in pre­vi­ous stud­ies.

The investigators found that a word’s “Page­Rank” was a good pre­dic­tor of how of­ten it would show up when peo­ple were asked to think of words that start with A, with B, and so on.

When it came pre­dict­ing these re­sults, “Page­Rank” beat two oth­er seem­ingly rea­son­a­ble rank­ing sys­tems: tal­lies of how of­ten words show up in or­di­nary writ­ing; and a sim­ple count of di­rect “links” to a word that does­n’t con­sid­er how many words, in turn, link to those link­ing words.

In the PageR­ank for­mu­la, a page gains “im­por­tance” based on how many oth­er pages link to it. But links from pages that are them­selves “im­por­tant,” con­fer more im­por­tance than those that aren’t. Thus, im­por­tance can be thought of as flow­ing through the Web’s link net­work to­ward the most highly “linked-in” sites.

One ex­plana­t­ion for the new find­ings, wrote Grif­fiths and col­leagues, could be that con­nec­tions among brain cells work si­m­i­larly to Web links. Cells that are tar­gets of many con­nec­tions might be­come more ac­tive than oth­ers, in the same way that highly linked-in web­sites are deemed more im­por­tant.

“Our ap­proach in­di­cates how one can ob­tain nov­el mod­els of hu­man mem­o­ry by stu­dying the prop­er­ties of suc­cess­ful in­forma­t­ion-retrieval sys­tems, such as In­ter­net search en­gines,” the group wrote in the stu­dy, pub­lished in this mon­th’s is­sue of the re­search jour­nal Psy­cho­log­i­cal Sci­ence. The study al­so sug­gests brain sci­ence might help de­sign bet­ter search en­gines and data-retrieval sys­tems, they added. “These prob­lems are ac­tively be­ing ex­plored in com­put­er sci­ence,” they wrote, but “one might be equally likely to find good so­lu­tions by stu­dying the mind.”