A trigger object is an inanimate object such as a toy, personal belonging, or other object associated with the deceased, which is used to attract the entity's attention or possibly capture the object in motion by creating possible physical contact of the object by the entity.
In the photo below a teddy bear is being used to try and entice the spirit of a child which is reported to have been seen or heard in this location while being filmed by a static infra-red camera.
Many investigators will use items like toys, i.e. stuffed animals, balls, etc., when dealing with the ghosts of children who have passed on, due to the playful nature of a child's mind. It is a way of not only drawing the ghost close to you but also gives it confidence that you are not there to harm it, but just to play and contact it.
There have been instances where a small red ball was placed in a bedroom or hallway by an investigator and then moments later the object in question was moved from its origin of placement. To simply put an object down and see if it moves throughout the night is not enough. The investigator must make the area quarantined, by either sealing off the room or area in question and making video graphic notes on it as well as having another investigator there to validate the experience.
The entities of children are assumed to be playful and most of the time, you may get a response, but there have been instances where the spirits of children have been known to be a bit “disrespectful” for lack of a better word and may cause havoc in a location that is presumed “haunted”. These spirits have a tendency to cause confusion & mischief, but again, you have to remember since they were once alive, theoretically, they are now what they were then, children.
On the other hand, when dealing with an adult entity you have to be a bit more scientific to see if you can not only appeal to their nature but also see if the possible movement can be caught on video. Theoretically since the spirits of adults tend to bind themselves to earthly possessions, people or places, one has to (if at all possible) try to associate that entity's manifestation with an object that was a personal possession of that person, i.e. keys, pen, photo, etc., and see if they are drawn by the presentation of an object that was once theirs, if at all possible. If not, then one must try to use a similar object to see if that entity will associate itself with that particular piece.