[NaOH]

Shouldn't the top result inherently represent what Google thinks is what I want? Or is there some secondary "confidence" component to the presumed efficacy of a top result?

[stellar678]

I'd presume they could look at the difference between their confidence (relevance?) in the first and second results. If the difference is more than some threshold, bam preload the first.

[abraham]

As I understand there is a secondary confidence score. Sometimes there just aren't any good results to show.

[ehsanu1]

Possibly click-through rate, normalized using average click-through rate for the first result.