navigate an obstacle course and to chain behaviors together. Chicken training is done using operant conditioning, using a clicker and chicken feed for reinforcement. The first chicken workshops were given by Keller and Marian Breland in 1947–1948 to a group of animal feed salesmen from General Mills, in Minneapolis, Minnesota. Trained chickens may be confined to a display (Bird Brain) where they play Tic-Tac-Toe against humans for a fee, invented by Bob Bailey and Grant Evans, of Animal Behavior Enterprises. The moves were chosen by computer and indicated to the chicken by a light invisible to the human player. Fish and molluscs Fish can also be trained. For example, goldfish may swim toward their owners and follow them as they walk through the room, but will not follow anyone else. The fish may swim up and down, signalling the owner to turn on its aquarium light when it is off, and it will skim the surface until its owner feeds it. Fish have also been taught to perform more complicated tasks, such as fetching rings, swimming through hoops and tubes, doing the limbo and pushing a miniature soccer ball into a net. Fish have been taught to distinguish and respond differently to slight differences in human faces displayed on a screen (archerfish) or styles of music (goldfish and koi). Molluscs, with totally different brain designs, have been taught to distinguish and respond to geometric symbols (cuttlefish and octopus), and have been taught that food behind a clear barrier cannot be eaten (squid). Wild animals Zoological parks Animals in public display are sometimes trained for educational, entertainment, management, and husbandry behaviors. Educational behaviors may include species-typical behaviors under stimulus control such as vocalizations. Entertainment may include display behaviors to show the animal, or simply arbitrary behaviors. Management includes movement, such as following the trainer, entering crates, or moving from pen to pen, or tank-to-tank through gates. Husbandry behaviors facilitate veterinary care. It can include desensitization to various physical examinations or procedures, such as: Cleaning Nail clipping or stepping onto a scale voluntarily The collection of samples (e.g. biopsy, urine) Such voluntary training is important for minimizing the frequency with which zoo collection animals must be anesthetized or physically restrained. Marine mammal parks Many marine mammals are trained for entertainment such as bottlenose dolphins, killer whales, belugas, sea lions, and others. In a public display situation, the audience's attention is focused on