We wait in anticipation for our babies’ gurgles to turn into speech, but how does it all develop? Paediatric neurologist Dr Amith Keshave explains the process.
Speech and language development is initially not as apparent as a child’s motor milestones. It may not even be noticed by parents, but it happens as early as the first month of life.
The baby goes from understanding receptive language (which is what happens when you talk to your baby) to expressive language (which is the way your baby communicates with you) within the first year.
This occurs initially as non-verbal language, and as the child learns to pronounce words, they start with verbal language. To explain this a bit further, receptive language is when you shake your head to say ‘no’ or ‘yes’, or tell your baby to smile and the baby understands. As your baby grows, these cues are quickly picked up and he in turn does the same to you for a similar response. This is the form of non-verbal communication that babies learn.
Language needs to be present first before speech can form. As a result, in a child who presents with speech delay, one needs to establish if they have a language disorder or a pure speech disorder. For example, if a child doesn’t speak, but is able to understand verbal instructions, then he has a speech disorder. A child who does not understand simple commands and therefore does not speak would probably have a language disorder.
The hearing-brain-speech connection
Language is identified by speaking to babies. And in order to develop normal language, you need to have normal hearing. Sound waves are transported from the ear across the ear drum (tympanic membrane), transferring the vibration across the middle ear via three small bones called ossicles, which take that vibration to the inner ear, where an apparatus known as the cochlear converts the vibration into electrical impulses that travel to the brain.
The impulses go to the auditory part of the brain that identifies sounds like a car engine, birds singing and the spoken word. These impulses are then transferred to the language area of the brain, which is situated in the dominant hemisphere. The language area interprets the meaning of the sounds, which allows understanding of the spoken words.
From the language area, impulses then need to be created by the motor area of the brain to send signals to the mouth, tongue, respiratory muscles and vocal cords (voice box), to produce sound. Any area that affects this complex pathway can affect the normal development of speech.
Causes of speech delay
The most common cause of speech delay is chronic middle ear infections, which affect the way that the vibrations are carried across the tiny bones (ossicles). This results in decreased impulses to the auditory part of the brain, and ultimately, speech is delayed.
Up until the age of three years, language and speech development are key. Studies have shown that delays in language and speech that are present after three years, require prolonged rehabilitation. This is why screening for hearing is so important – a child doesn’t truly form words until one year of age, but can have a hearing problem from birth. This means that the child could have received treatment at an early age, preventing long-term complications.
Speech developmental milestones are as follows, but please note these are not absolute values, and ranges for each exist:
- Birth – they cry to their needs. This is the first way a baby learns that vocalisation (making a sound, like crying) will result in a response such as feeding or comfort.
- 1 month – responds to a bell or rattle (does not necessarily turn to the sound).
- 2 months – starts to ‘coo’, saying things such as “Ah,” and “Oh.”
- 3 months – localises to a rattle (turns to the sound).
- 4 months – laughs and squeals.
- 5-6 months – monosyllablic babbling (non-specific “Mama”).
- 7 months – imitates speech sounds.
- 8-9 months – polysyllable babbling (baby talk).
- 10 months – specifically identifies Mama and Dada, or primary caregiver.
- 11-12 months – single words start to form (car/ball/Mum/Dad)
- Between 2-3 years of age – the child says two-word sentences (Come play./Let’s go.)
- Between 3-4 years of age – the child says three-word sentences and thereafter vocabulary advances exponentially. They become ‘parrots’ with non-stop talking as they practise their newfound skill.
When to seek help
- Consider seeing a specialist if the following are noted:
- At birth loud noises do not startle your baby – this may indicate a hearing impairment.
- At six months of age, if your child is not able to turn to a rattle.
- At nine months your child is not babbling (baby talk – mono or polysyllable).
- At one year there are no single words being attempted or formed.