Indirectly, ear infections can lead to the congestion of inner ear canals that interfere with proper hearing. Because very young children and toddlers’ auditory structures aren’t configured yet the same way as adults, the fluid that accumulates aren’t always drained and ends up staying in the ear causing ear infections.
This in turn simulates a hearing loss and prevents the toddler from hearing the spoken language correctly enough to acquire language. It is one of the reasons why doctors sometimes put “tubes” in babies’ ears, which would then be pushed out naturally after a year. However, this can’t be done as easily in toddlers because they naturally do not want to stay still while a doctor puts a tube in their ear – they will have to be anesthetized (general).
I attended an information seminar on this subject and the speaker gave this demo: Insert one of those foam ear plugs into your ear. Now have someone stand in front of you and speak – have that person move to one end of the room while you stand at the other end and try to hear. Now have that person turn his/her back while speaking. Most of us in the room could barely make out what the speaker was saying. And we already have language and have the tools to make educated guesses! We rely on visual cues to help with our language and decipher what the other person is trying to say, but when we lose this cue, or if we don’t understand this cue, then that’s a bit like what toddlers with hearing loss experience.
There is also a difference between “sounds” in general and “language sounds”. Thus, just because a toddler can hear sounds, it doesn’t mean he or she can hear language sounds. The best way is to go to an pediatric audiologist with the equipment that can test both pure sound field hearing and speech sounds in both ears.
My answer is based more on indirect causal effects, the website below discusses an interest in learning the effects of hearing and language acquisition/development: “Understanding the impact that ear infections have on a child’s speech and language development is another important area of study. Creating more accurate methods to diagnose middle ear infections would help doctors prescribe more targeted treatments. Researchers also are evaluating drugs currently being used to treat ear infections, and developing new, more effective and easier ways to administer medicines.”