Fascinating. Shows the importance of actually testing and measuring. I would have guessed the reverse, that everyone is used to the "back" button by now and almost nobody would bother looking for a needless extraneous one actually contained in the site.

I'd be interested in learning what these users do when faced with a site without navigation links. Do they just close the browser and re-type the original URL?

i question the validity of your test and/or it's application in the current context.

what I am hearing is "the average non-technical person incapable of using Google."

These people weren't incapable of using Google or computers. Some users were business-types who are used to using a lot of web-based SaaS tools and quite capable and comfortable using computers.

By non-technical I really meant they weren't developers; they were sales, marketing and management type people.

When asked, it simply didn't occur to most of them to simply press the back button.

Now, its not apples to apples, of course, and since this was in a web app where there may well have been a fear that pressing back would lose the page like you do in some (badly designed) single page applications, its possible that this skewed the results somewhat. Either way, we found that adding in-page navigation improved the workflow for almost everyone.

but how they use your application is not a reflection of how they use the web at large.

i'm not surprised by your study's result, I'm just not sure you can extend your conclusion to believe that people won't or can't click the back button to return to Google after clicking a result.

Oh. That's why Google has the insane "Google and X to back" behaviour. I guess they assume power-users will use the Chrome browser and newbies will use Google and need the redundant X-bar.