You might find this study interesting. The paper sensationalizes it a bit IMO by classifying people as "bullshitters" when it seems to me more like "overconfidence" in their knowledge. Quality of the study/headline aside, I do wonder if there's a selection bias for knowledge overconfidence in engineering as parent comment suggests. I would imagine people who make good engineers are the type who aren't intimidated by "knowledge gaps" and they assume (rightly or wrongly) that they'll be able to figure out a solution even where they have little or no expertise.
 [PDF] http://ftp.iza.org/dp12282.pdf
Link to study:
A new study of the phenomenon has found that North America is especially prone to speaking bull. John Jerrim, Phil Parker and Nikki Shure, three academics, have used an educational survey of 40,000 teenage students in nine English-speaking countries to find out who is most likely to spout nonsense. They inserted a section into the questionnaire which asked students how well they understood a collection of 16 mathematical concepts. Some were familiar, such as “polygon” and “probability”, but three were fake: “proper number”, “subjunctive scaling” and “declarative fraction”.
The results show substantial differences between countries. Canadian and American teenagers were especially likely to profess knowledge of these bogus topics, whereas the Scots and Irish were perfectly happy to admit their ignorance. In news that will shock nobody, in every country men claimed to be experts more often than women. The rich were more boastful than the poor. More surprising was the finding that immigrants were generally more likely to bluff about maths than native students were.
What explains these differences? The academics doubt that the bullshitters were simply trying to impress the questionnaire’s markers. The students who bluffed about maths were just as likely as the non-bluffers to admit that they had skipped school recently, for example. A more likely answer is that the blaggers over-estimated their own knowledge. They also tended to rate themselves highly when it came to gauging their own popularity, perseverance on academic tasks and problem-solving ability. The data suggest that they might not be consciously lying, but instead be weaving their own fantasies.