While that's a 65% increase, the findings do not explain why the behavior has changed so markedly in two years, and whether, for example, it's a function of more content being available in HDTV.

That could be at least part of the reason though, as Knowledge Networks Vice President-Group Account Director David Tice notes that there has been a significant increase in the frequency of viewing of certain genres of programming - such as "how-to" and news content - that "we wouldn't have associated with HD a few years ago."

The percentage of HDTV viewers watching "how-to" shows in HDTV has more than doubled to 26% from 12% two years ago. The percentage of HDTV viewers watching evening newscasts in HDTV has jumped to 31% from 22% two years ago.

The new study also finds significant differences in the consumption of HDTV programming by gender.

Men are much more likely (48%) than women (19%) to check HDTV channels first when turning on their TV sets, and men (58%) are also much more likely than women (41%) to choose HDTV over standard definition programs when both options are available to them at the same time.

When it comes to TV commercials televised in HDTV, men and women are equally split. Men (42%) are more likely to notice ads are not televised in HDTV than women (20%), but women (24%) are more inclined to purchase brands or products that advertise during HD programs than men (15%).

"This sends a message to advertisers that [HDTV] is becoming the new norm for those with [HDTV] access across all program types," Knowledge Networks' Tice states. "An important learning for companies targeting products to men - who are more likely to seek out [HDTV] programming and to recognize the difference between standard and high-definition ads - is that creating advertising that is more relevant to the male audience could make you stand out from the [HDTV] crowd."

This news story is important. I recommend that everyone read it.