The Mother of Six-Month-Old Robbie Makes a Cooing Sound to Him

Multiple Choice

The mother of six-month-old Robbie makes a cooing sound to him until he becomes bored and looks away. She then clicks her tongue, which makes him look at her again. Robbie has

A) demonstrated preference.
B) voluntarily delayed his reaction.
C) developed an auditory defect.
D) displayed dishabituation.
E) responded to operant conditioning.