That's interesting. Why would they learn fewer words? Do the less wealthy just talk less? Or, do they learn other words that are then culled from their vocabulary?
There is no way to say this without sounding like an asshole, so I'll just forego trying to sugarcoat it: I can read perezhilton.com without ever having to look up a word. Reading the Economist, I have to look up at least one word every week. Growing up, I never knew a single person reading the Economist or the equivalent; while reading the spatial-and-temporal equivalent of perezhilton.com was though of (by my larger environment, not my nuclear family luckily) as something that was almost intellectual, because hey, it was reading.
(I'm a non-native English speaking currently middle class European from a semi-rural area and from a working class background)
(I'm a non-native English speaking currently middle class European from a semi-rural area and from a working class background)