Ghost hunters use trigger objects to draw or lure spirits out. It is one way they can communicate or interact with them. The goal of a trigger object is to see if it will move.
To lure spirit children a ball will be put down for them to play with. On one investigation we had a spirit child literally pushing the ball back to us after we rolled it across the floor. This floor was level, there was not a slope or slant that caused the ball to roll back. In fact, earlier in the evening in the lobby of the office were we were investigating the ball stayed still in the same places that it later rolled back to us.
Many ghost hunters will not use balls as trigger objects because they easily move on their own. I use them because they do attract spirit children. But I have found it is best not to use an object that might fall over easily, such as, stuffed animals etc.
The general consensus is, once you have an object that won’t move on its own, place it within a circle or on a piece of paper and draw a line next to it. A variation on this theme is to place a filled drinking glass on a layer of flour. Then put it somewhere where your group will not disturb it and aim a camera at it. Also place a meter next to it (Kll etc.) and see if your camera picks up any fluctuations on the meter when the object moves.
A trigger object just gives the spirit a way to show they are there. Last year we placed a flashlight in the loft above us of a store where we had picked up activity in the past. One of our DVR cameras caught the light from the flashlight being turned on and off. I find it is best to use trigger objects that are small but large enough to see on a camera.
Always tell the spirit or spirits why you are placing the trigger object in their space—“We want you to move this (glass etc.) for us so we know you are here.”
Happy Ghost Hunting!