Schematic of the test setup, including the 4-ft × 5-ft response mat placed on the floor of the sound booth. The child stood on the star-shaped cutout facing the two red circles to the front-left and front-right of the star, which displayed pictures of cows and frogs corresponding to the no-change and change responses. Lighted, animated toys in smoked, Plexiglas boxes sat in front of each response space for immediate, selective reinforcement. The reinforcement controller and a keyboard for entering responses were placed to the left of the experimenter. A monitor placed on a table at the child’s eye level displayed the orientation cue. Speakers were placed at ±45° azimuth. Figure is not to scale.