Matthew Mcconaughey's 20-month old son speaks better Portuguese than he does.

The 'Fool's Gold' actor insists his failure to grasp Brazilian girlfriend Camila Alves' native language is actually good for their relationship because it means she can vent her feelings about him more freely.

Matthew - who has son Levi and nine-week-old daughter Vida with Camila - explained: "Levi speaks a whole lot more Portuguese than Papa does. I get a little heck for it in the household.

"I've come to find that I do think it is actually healthy for our relationship that I don't speak that much Portuguese because she doesn't have to whisper if she's talking noise on me. She can speak out loud.

"I don't know what she's saying, but it sounds great... someone can say something about you right in front of your face and you don't even know it's about you."

The family are delighted with their newest addition, and the 40-year-old star admits the baby's routine is "pretty simple" for the time being.

He explained to US TV talk show host Jay Leno: "They eat, they c**p, they sleep and if they're crying they need to do one of the three and they're having trouble doing it. Real simple."

While Vida is easy to look after, Matthew says he and Camilla are unable to take their eyes off Levi because he is so inquisitive.

He said: "Levi is into everything. You don't go out and walk in the backyard and daydream for five seconds or he's on top of the house.

"He's either going to be an astronaut because he's always like Air Traffic control from a bird to a plane, sun, moon, cloud, everything in the air. Or he's Poseidon because he's infatuated with water - 'Agua, agua, agua' - for hours.

"If he meets you he looks you down to up, he sizes you up ... he looks at your shoes, checks you out, and then he's happy to meet you."