Context. Simulation of nature is something that is used to immerse the player into the world of games. By adding details in the world such as birds circling in the sky or small fishes swimming in a flock, developers can improve the gaming experience for the user. More precise simulations are something that should be aspired for. This thesis will explore the boid flocking algorithm and evaluate what settings users perceive as realistic behavior for simulating schools of fish. Objectives. This thesis proposes that there should be a set of variables that reflect a more realistic behavior and through gathering data from volunteers and mapping their answers, conclude if that statement is true. Methods. A boid simulation will be run in a number of different scenarios, each differing in variables that are vCohesion, vSeparationand vAmount that make changes to the overall behavior. This behavior is then recorded and compared next to each other in a perceptual experiment with the objective of finding out the preferred settings interms of realism. Results. The experiment showed that the preferred value of vSeperation was around 50 to 60 world units. The value of vCohesion and vAmount was random to what was perceived, so their impact on realism was not significant enough. Conclusions. After running the experiment it was apparent that there was a preferred value on some of the variables that were examined. The larger impact on realism was in the distance each boid wanted to keep from its neighbor, the vision range of each boid defined what was considered a neighborhood. The range on this variable was not of much importance and did not impact what the user perceived as realistic.