I've started buying half a dozen at a time, dumping them all on the floor together, and just letting my two geniuses pick whichever one they want. The younger one always rushes to be the first to grab one and then is immediately dissatisfied when she sees that her sister also got one -- apparently one that is even smellier. Does she go back and pick up one of the remaining four hooves that are fair game? Of course not, she sits there brooding for 20 minutes until her sister gets up for a drink and then immediately steals the one she was chewing on.