Google’s head of search spam, Matt Cutts, posted a video answering another webmaster question. The question was, “Are results in different positions ranked by different algorithms?”
The answer is no, Google does not have reserve web search results slots or positions for ranking for specific algorithms.
For example, slots 3-5 in the results are not reserved for fresher content, while slots 6-8 are not reserved for more authoritative content. It does not work like that. Google has algorithms that ranks all the search results and the algorithms are not assigned to specific positions.
Here is Matt’s video answer: