I think that the number of one-sided conversations that I have had with people over the last five years have been higher than "normal." So, I am guessing that the cause was low self-esteem on my part -- the conversations would have been two-sided had I asserted myself. The alternative explanation could be that I just got unlucky with social bores. Either way, if there is a definition, or profile of low-self esteem I'd be curious what others thought it might be.