Paediatricscommon
A 22-month-old boy is brought to his general practitioner because he is not yet talking. He says 'mum' and 'dada' only, but points to things he wants, waves goodbye, and enjoys interactive games with his older sister. His parents note he often does not respond when called from another room, although he turns quickly when they clap or when he can see them speaking; he has had four courses of antibiotics for ear infections in the past year. He passed his newborn hearing screen. Which one of the following is the most appropriate initial investigation?