Can peeps shed some light on wether one search engine ranking effects the other?

Also and most importantly, in a way you do not expect!


for example, yahoo rank decreasing everytime your google rank increases. I.E. one does not help the other but worsens the other.

I am sorry, i am new to SEO and have no stats for my site to show. It just seems when one search engine rank increases it balances out with the rest decreasing, so i cant win!