They will run towards enemies like psychos. When they get to midrange, they pause for a second preparing their leap attack. A good strategy is to wait until they pause and utilize a shotgun to take them down quickly. They tend to do low damage, but will daze and should normally be of low priority to kill, especially since they can take some time to locate. It is easy to know when they are coming due to their higher-pitched shriek. Normally, they come after the first wave of zombies has arrived and function as a nuisance and distraction but their leap attack and speed can overtake enemies who are passing through.
Even though their models are based on Midget Psychos they do not have the mask that psychos usually wear.