I have no dispute there. But I get the impression (mostly from people who are of relatively modest intelligence themselves) that it is relatedly often presumed that people with lower intelligence are naturally more friendly and less guarded than more intelligent people are.
That strikes me as incorrect. It doesn't take much time spent in public in a poor area to feel a default hostility almost emanating from the denizens, especially young men. In contrast, politeness and common courtesies, like holding the door or offering a parking spot to another person waiting for it, appear to be in abundance in upper class areas.
It seems more intelligent people tend to be naturally more friendly and more polite than less intelligent people are. That less intelligent people are more likely to be receptive to dubious promises is a result of being less able to discern the differences between what is being billed and what is actually being offered. So ten minutes into a bogus sales pitch, a high IQ guy may look like he's being a jerk to the seller while a low IQ guy may be signing the clipboard the seller has handed him. See the same interaction within its first ten seconds, and most of the time it'll be the high IQ guy who is at least feigning interest in what the seller has to say while it is the low IQ guy who is grimacing as the seller starts his pitch.
The GSS interviewers are asked to describe respondent attitudes towards being interviewed. They have done so in 22,897 cases going back to 1972. The average IQ* by way of Wordsum scores for each of the descriptions (in order of how accomodating the interviewer believed the respondent was):
* Based on the presumption that the average white Wordsum score is the equivalent of an IQ score of 100. Unless it is otherwise noted, "white" probably refers to about half of Hispanics interviewed (disproportionately those with more European ancestry, presumably). Until 2004, the GSS only asked if a respondent was white, black, or other. It has since added a more expansive question on racial self-identification, but that is of course only useful if there is not an interest in anything prior to 2004. So using this method to identify the Wordsum equivalent of an IQ of 100 might inflate the conversions a little. However, for the nearly 23,000 respondents used in constructing the table above, an average IQ of 98.2 is suggested. Since it is looking at all races, that's very reasonable.