There was an informal experiment done a while back
see here that looked at the effect of clickthroughs on a listing in Google, and the effect of bounces recorded in Google Analytics that seems to indicate both these factors may play a small role in how a page shows up in Google's SERPs.
NOTE: Bear in mind that unless the user has the Google toolbar installed or the webmaster uses Google's Analytics, Google has no way to track user behavior beyond the landing page.