Curious speech

I just returned from a week where I was in crowds of people of different racial and cultural backgrounds from those I usually encounter. One thing that struck me during this exposure was the wide-spread use of "ja know what I mean?" in almost every sentence during almost all conversations I overheard. I presume this is an extension of the previous verbal assault "you know" which became a common source of lingual criticism and derision.

My question concerns the origin of this practice. So far I have come up with two possibilities. The first is the individual has no confidence in his or her ability to communicate effectively and just wants some assurance that all the words actually mean something. The second is the person speaking has no confidence that the person being addressed is smart enough to understand the spoken words. In either case, a desire for reassurance by constantly asking "you know what I mean?" makes sense, but the deficiencies implied are not particularly flattering.