In this videotaped test, the infant watches an animated toy animal while a single speech sound is repeated. After a few repetitions, the sound changes and then the display changes, and then they both change again. If the infant switches her attention when the sound changes, she is anticipating the new display, which demonstrates that she can discriminate between the sounds.

COURTESY DR. PATRICIA K. KUHL, UW INSTITUTE FOR LEA RNING AND BRAIN SCIENCES