Researchers are discovering that smaller type encourages people to read the words where as larger type promotes scanning.
This was especially the case when we looked at headline size on homepages. Larger headlines encouraged scanning more than smaller ones – an appropriate balance is important.
Users tend to view both the headline and blurb when the headline was bold and the same size as blurb text and immediately preceded the blurb on the same line.
With a headline larger than the blurb and on a separate line, people tended to view the headlines and skip the blurbs; they scanned the headlines throughout the page more than the group that looked at the smaller headlines. If the headline is larger than the blurb text people appear to decide that viewing the headline is sufficient and they skip the blurb.
Underlined headlines also discourages users from viewing blurbs on the homepage visual breaks — like a line or rule — discouraged people from looking at the blurb below the break.