you have the mind of a ten year old.

you think like a ten year old.

good luck
igli

Ciao Drem, this is a common expression in U.S. English for people who do not act/feel their age:

... Jamie Murray age 40 something going on 20 surfing industry, Billie age 8 aussie shepherd/border
collie mix, HT (herding tested) President of Dogs for Democracy. ...
www.fringefolk.com/fringepage14.html - 26k - Cached - Similar pages

... preferable). I am 27 years old (going on 20) and am a thin swimmers build. ... preferable).
I am 27 years old (going on 20) and am a thin swimmers build. ...
www.biphoto.com/figuremodel/messages2/5294.html - 4k - Cached - Similar pages

... Next Review. My Niece is 13 going on 20 By : rosie6349. Sep-23-01 6:20 PM.
My niece likes so many things it is never a problem buying her a gift. ...
www.mouthshut.com/readreview/14404-1.html - 47k - Cached - Similar pages

... she becomes frustrated when she and her unpopular friends are ignored by boys, whose
attention is fixed on Evie (Nikki Reed), who looks and acts 13 going on 20 ...
www.capeweek.com/thirteen21.htm - 15k - Cached - Similar pages

.

ciao

prima espressione: usandola si indica che la persona in questione si comporta o pensa come uno di 10 anni ma non solo in termini di buon senso. I motivi sono lasciati aperti ad interpretazione (potrebbe riferirsi anche all'ingenuita' dei 10 anni per esempio)
seconda espressione : piu' mirata alla maturita'- variante piu' specifica " you've got the common sense of a 10 year old"- quest'ultima e' la traduzione piu' esatta ma con meno sfumature