The science on a psychological level? I know I personally am quite likely to speak up against something I disagree with. I will do the same in reviews. I'm more likely to leave a bad review than a good one, unless I've come across something that goes above and beyond, then I'll make sure they are aware of their awesomeness. On these technology subs in particular I'm more likely to output a negative view, since technology is something that is easy to be critical of. I also often will say something if I disagree but what I'm disagreeing with has a lot of upvotes. For me, this unfortunately creates a profile in other people's minds of what I'm like irl haha. I feel that most people would quite likely not disagree with something popular for fear of the backlash they would get and in turn get downvoted and lose karma. I personally don't care for karma beyond it being an interesting metric of people's opinions and how those opinions are shaped depending on what has been upvoted/downvoted before they come to read it.