They're all brilliantly funny, but which star of Modern Family is an honest-to-goodness genius? None other than young Nolan Gould, who — ironically enough — plays Luke, the slowest member of the Dunphy clan. His Twitter description states, "I am not a dummy, I just play one on TV."

Credit: Eric McCandless/ABC Television Group © 2011 Disney Photo: Luke Plays in Modern Family Season 2, Episode 5: "Unplugged"

Nolan told a Twitter follower recently that he keeps his IQ a secret, mainly because he doesn’t want people asking him tough questions to make him prove it. But it has to be at least 130 — you have to score in the 98th percentile or higher to quality for Mensa.

"My brother and [I] have been members of Mensa since we were about 4," he told Smashing Interviews Magazine. "We had to take a test for school purposes, and they found out we could go into Mensa. It's a really great organization that gives you a lot of resources, and you can meet other people. It's really cool."

In a January 2011 appearance on Jimmy Kimmel Live!, Nolan's co-star Ariel Winter (Alex) revealed that 12-year-old Nolan takes classes on-set at a ninth grade level. Ariel and Rico Rodriguez (Manny), who are the same age, study at seventh and sixth grade levels, respectively.

So how does the undercover Einstein feel about playing Modern Family's most, uh, intellectually challenged character?

"The best thing is that he's not like me and I get to do a lot of physical comedy," Nolan told Entertainment Weekly. "I get to be another person when I go to work."

Modern Family producer Christopher Lloyd says Luke's intelligence makes him an even better actor on the set. "He's a brain-first kind of guy," he told EW. "He'd listen to you and process it, even when you were talking to him about what expression you wanted him to have on his face when his head was caught between two banisters and his father's greasing him up with baby oil to pull him loose."

Sources: Smashing Interviews Magazine, Entertainment Weekly