Players are assigned a broad category to reference. The categories must be broad. For example, cars, toys, cutlery, food, etc. Then they make endlress references to the category.
Once the players are milling about the room the leader asks them to raise their left hand and mill for a bit longer. When the chain reaction is started each player must find a left shoulder to rest their left hand on. A shoulder can only support one hand at a time. A left hand cannot rest on a right shoulder. The hand shoulder bond should not break after being connected.
The players stand like statues but keep an eye on each other. One players starts to mill around the room. Briskly moving in and out and around the players standing still. The player must try their best to maintain eye contact with the solitary milling player.