In a little over a week, an important part of Obamacare will be rolled out across the country. The health insurance exchanges open for business on October 1.

Except “most people don’t understand Obamacare” says Peter Ubel, a professor at the Duke School of Public Policy. He says “uncertainty can be a very powerful emotion.”

And emotion has been a constant theme in advertisements about the health care law.

“I think both sets of ads on pro-Obamacare [and] anti-Obamacare are working off fear,” says Ubel.

Ads like the much lampooned Uncle Sam giving a prostate exam are one example:

Could these ads actually stop people from signing up for health care? Ubel says “it will scare people and that will work.” Some will be too scared of the government to sign up. Others will be too scared of high health care costs not to.