Affectiva, a startup that tries to measure the emotional response people have to ads and brands, just announced that it has a $500,000 grant from the National Science Foundation.

The company spun out of MIT’s Media Lab. This is its second NSF grant — in January 2011, it won another grant to help launch its Affdex service, which uses webcams to track consumers’ responses as they watch videos. That should allow companies to test their ads with a broad audience in a quick and affordable way. When I spoke to co-founder Rana el Kaliouby last year, she also touted Affectiva’s ability to recognize complex emotions — not just whether you’re smiling or frowning, but also whether you look confused.

Among other things, Affectiva says its technology has been used to crowdsource readers’ responses to ads at Forbes.com, and that it worked with research agency Millward Brown to test Super Bowl campaigns. In addition to Affdex, the company also offers a wireless biosensor that it calls the Q Sensor.

Affectiva says it will use the grant to continue developing Affdex, and to build an “emotional norms database,” which is supposed to answer questions such as “How does an ad’s emotional engagement compare to other ads ?” and “How do people in different countries respond to humor in a campaign ?”

The startup has also raised venture funding, most recently a $5.7 Series B. Eventually, Affectiva says its technology could expand beyond ad testing, for example by helping people with autism disorders understand facial expressions.