The experimenter pressed buttons on a computer-controlled response box to indicate when the infant looked toward or away from the flashing light (the source of the sound). The total time spent looking on each trial was recorded on the computer; any time the infant spent looking away from the light (whether 2 s or less) was not included in the total duration of the child’s looking time. The experimenter and caregiver wore Peltor aviation headphones playing masking music in order to avoid
biasing the child’s behavior or the coding of that behavior.