From Creatures Wikia
Mind Arrows is an agent that forces nearby norns to follow the arrow's directions. If the arrow is pointing left, all creatures near it will walk left. If it is pointing down, all nearby norns will use the lift to go down (or call the lift if it is not there). Clicking on the arrow will change its direction. These arrows can be used to create a path to lead all norns to a certain area, or as a sort of mental forcefield to keep them away from somewhere.
Warning: Mind arrows work by quite literally mind-controlling the affected creatures. Be careful not to create a path that leads creatures into a circle with the mind arrows, because the creatures will follow the arrow's instructions until they starve.
Notice: When positioning mind arrows to point up or down, make sure to place the arrows where they are touching the elevator (or will be when it is called).