I confess that I am affected positively when hearing an English accent. As a frequent stumbler, they sound more articulate than I could ever hope to be (rightly or wrongly). And my soccer commentators must be English, no substitutes, though I suppose a Scotsman could handle the second chair in a pinch.
The posh accent is usually associated with someone with an excellent education. I’ve got to expat Brit friends (they don’t know each other – I think) with the same accent and type of education. They are really smart.
Michael Caine is a good example of this. He speaks with a Cockney accent that doesn’t sound upper-class in Britain. But it sounds classy to us here in America.
But you’ll notice that even Mr. Caine has lessened his Cockney from his earlier days in acting and that he can do affect a RP accent quite capably ( Zulu Dawn for example) when he chooses to.
IMO, a lot of people in the US think of PBS and the BBC when they hear an English accent. Both of those media outlets are seen as being “highbrow” to the average person and many equate that with them being smarter.
When I was stationed in England in the 1980s, I did find that many British people were certainly more well-read than most Americans. They were able to clearly and concisely discuss novels and concepts ( sadly even those of American writers) which were often beyond the grasp of most of the military members who were stationed there. Whether or not this made them “smarter” is debatable.
However, many of the GIs over there thought that they were smarter, so there is that.
I only trust Irish accents to tell me what soap to buy and which breakfast cereal to eat.
Some time ago, I would have agreed to it sounding smarter.
But starting with Benny Hill and then especially since Russell Brand, my opinion has eroded.
But I could still listen to a woman with a British accent all night long…
Yep, I think so.
Most upper-class foreign accents sound “intelligent” even to me, as a person raised upper-middle-class by lawyers and living much of life in intellectual, multicultural environments like university towns.
I bet a lot of people also associate a number of other foreign accents as intelligent, especially Indian and Chinese, because an awful lot of people with these accents had to overcome significant hurdles to come here to the US, and most of them have a different work ethic than native-born Americans, giving many of them both environmental and hereditary advantages.
lol
I bet Mr Caine could sound intelligent with a whino’s speech pattern, or like an idiot with a Cambridge professor’s accent. It’s called acting.
And no doubt he sounds intelligent speaking in his natural accent, simply because he is. Or at least, if he isn’t, he sure has fooled me.
That doesn’t quite negate your point, though. My suspicion is we Americans tend to think Cockneys are clever, even ones on the skids like Mr Doolittle. I wonder where we got that impression.
We had some Scottish neighbors once and their 3 sons had these Scottish/British accents that the American girls in their schools just swooned over. Granted they were good looking also. They practically had to fight the girls off.
I told one kids, “dont ever lose that accent of yours”.
OTOH Australian accents, popularized by the Crocodile Hunter, make Australians seem so darn fun.
Whereas I associate Oxford English with smarts, but a more general English accent thanks to Monty Python seems to always have ironic or zany humour (with a “u”) hidden in it. Of course, a steady diet of Benny Hill, Two Ronnies (“I’m from the third world… Yorkshire”) Are You Being Served, On the Busses, Man About the House, etc. - not difficult to figure out the lower class oy-I’m-funny accents.
And everyone knows from the original Star Wars that the Dark Side has British accents.
His normal speech patterns don’t sound classy to me. Quite the opposite.
It’s not a subject I know anything about, but Theodore Roosevelt’s accent never struck me as what I would think of as a typical American accent.
There’s definitely at least one British accent that works in reverse,at least, for me. It’s that Essex accent. It’s why it so thoroughly surprised me when Russel Brand turned out to be intelligent.
[British Accent]That’s a very interesting point of view, and I’m glad you shared it.[/BA] 
Quite.
Quite indeed.
This blog post references a number of studies on the topic.
-RNATB, US immigrant
Morningside possibly, Gorbals NO!
There are Scottish accents that ooze trust and those that ooze threat!
Translation for those hard of nuance
“Shut up and never offer me any advice ever again.”