I've been wanting to post the same question here, but martinibuster thankfully answered it, and did confirm what I experience as well. Well, I experience about 3 different ranking improvement phenomenon when building links to targeted pages. Here's what happens:
1. When the targeted page bursts out on to the 1st page of SERPS, it hangs there for a few days, then falls back to the 2nd page. It then stays on the 2nd page for a few more days or, it stays there for a few weeks before going back to the first page.
2. The targeted page gets pushed up to the 2nd page of serps, often in the top 15. And, often, Google will laugh at me by pushing it right to the edge at #11 where it hangs out for a week or two before finally moving to #9 or #8 or #7.
3. Google will sometimes recognize a link right away, and movement will occur, or it will cache the link and nothing happens right away and no movement takes place for 1week or more. Often, more than 1 week.
Can anyone else confirm these 3 types of link recognition movements by Google?
It seems that in my field, I can get any targeted page I want pushed to the 2nd page of the SERPS for 3 word combinations, but when it comes to the getting them to move to the first page, it's rather indefinite and I have much less ability to influence.