A pattern has made itself very apparent to me and I feel that I must share it so that the rest of the world may benefit. It involves a pattern in a danger that many have faced and how we approach this danger. New solutions may be found.
In old world stories about vampire and similar creatures, a person being pursued by the undead could throw grain or sand at the fiend. The vampire would be compelled to stop, pick up, and count every kernel before continuing with pursuit. This would not seem to be in the vampire's best interest.
It is also obvious that lower-functioning undead creatures, such as zombies and mummies, will pursue a goal while oblivious to all other events. (By "lower-functioning" it is meant those that do not appear to have complex reasoning skills or other higher thought processes.) In some cases, these undead things will keep after a even though there is an imminent threat to themselves.
In the class of incorporeal undead, such as various ghosts and specters, it is common to have to repeat the same behaviors for all time. Typically, the repeated event is a notable trauma from the time when the entity was still living. When the living try to interfere, or even just get in the way, the specter will try to incorporate the person into the repeated pattern.
These observations can lead to only one conclusion: there is a high incidence of Obsessive Compulsive Disorder in the undead community.
Obsessive Compulsive Disorder (OCD) is a psychological disorder where the patient's condition manifests itself through a pattern of repeated thoughts or actions. In the living, it may manifest as excessive hand washing, or an overwhelming urge to align objects in a specific way. The main difference between the disorder and a habit is that the disorder is causes the sufferer to perform these behaviors even when it goes against their best interests and the patient cannot stop the behavior.
In the case of the vampire and similar creatures, there is no rational reason to stop to count grain. This is obviously not in the vampire's best interest and the vampire would probably prefer not to stop when so close to a meal. My hypothesis is that the remaining human part of the vampire's subconscious is still appalled at the idea of biting a person's neck and drinking that person's blood. This causes a great deal of subconscious conflict which manifests itself in this excuse to drop the pursuit.
Ghosts are another issue. They usually result from death in a traumatic event. The trauma is obviously too great for the ghost to handle psychologically. In an effort to make everything seem right, it repeats the actions to make them normal. Obviously the ghost would be better off moving on to the afterlife, but that would require an acknowledgement that the traumatic event was wrong. The subconscious conflict manifests as repeated activities and interlopers, such as unfortunate humans meandering in, must be included to reinforce the "rightness" of the event.
The lower-functioning undead may not have the complexity to have a proper disorder. It may just be that they stay focused on their single minded activities because their minds are too simple to have more complex thoughts about anything. If this is the case, then they do not have OCD, though their repeated patterns may make it look that way. They may, in fact, only be following simple instinct and we must forget that their minds were once capable of more.
The important thing to remember about this observation is that, if it is true that the undead have OCD, then we can use that knowledge to minimize the threat posed by these creatures. In the case of ghosts, we can use the standard treatments for this trauma and its related patterns to help them move on. Of course, we do not wish to cure vampires of their OCD until we can first stop them from wanting to drink our blood. We may find that getting them to feed in a more civilized manner may result in the loss of the OCD just because it removes the subconscious conflicts.