On a site that people can vote on others' posts (like Stack Exchange sites), I believe people tend to be affected by the current vote score (and for Stack Exchange, if the user has enough reputation, the current vote counts as well) before they cast a vote, or even more, before they decide to whether cast a vote. A typical case is illustrated by this Reddit post,
I tend to upvote people who have been downvoted out of sympathy.
The linked Reddit post already contains part of the answer but it's more like a subjective discussion so I am not satisfied with it.
Can somebody elaborate on what effects can take place in this process? What is effect on the final vote count/score if we consider it as a whole? Are there any known terminology or models to describe this behavior?
I am new to psychology so any hint will be helpful.