Humans need contact with others and find comfort when in the presence of other people. Having nobody to rely on for aid can have a psychological effect on the player as nobody has their back. Its leaves the player relying on their senses. Sound effects, music, and the design of the environment heightens the player’s awareness to all these parts.

http://www.gamesradar.com/ways-horror-games-use-psychology-scare-crap-out-us/

http://uk.ign.com/articles/2014/09/16/the-rise-of-emotional-decision-making-in-games