How is the effect of current vote scores on people's votes interpreted in psychology? 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.



Related: Why do people make rants on Meta Stack Exchange sites?
I think you can find an answer from the field of social psychology. The most relevant theory is the social proof, the tendency to immitate the behavior of other people.


  Social proof (also known as informational social influence) is a
  psychological and social phenomenon where people assume the actions of
  others in an attempt to reflect correct behavior in a given situation.
  
  ...
  
  Social proof is one type of conformity. When a person is in a
  situation where they are unsure of the correct way to behave, they
  will often look to others for clues concerning the correct behavior.
  When "we conform because we believe that others' interpretation of an
  ambiguous situation is more accurate than ours and will help us choose
  an appropriate course of action", it is informational social
  influence.