Polling stations are open across the country with the election fast approaching, only four days away now.

However, who people vote for can be determined right on the spot. Everything from the order of the ballot paper to the physical place you cast your vote can all have an impact on who someone chooses on the day.

Auckland University lecturer in political psychology Danny Osborne told Kate Hawkesby says dependent on the election year, some people do vote on the spot.

"In an election year when we know the candidates pretty well, probably not too many people are going to be deciding on the day of... but when it's an election where we don't know really know much about the candidates, it's going to be a little more heavily influenced by undecided voters."

Mr Osborne says the order of candidates on an election form can also influence undecided voters.

He adds even a candidate's psychical appearance can lead to more votes.