How do our brains process speech? - Gareth Gaskell

Summary

The brain's ability to recognize and understand speech is a fascinating process, where multiple possible meanings are activated simultaneously as we hear a word. The brain's parallel processing system identifies the correct word through patterns of neuronal activity, known as the 'recognition point.' Context, prior knowledge, and language cues help the brain quickly settle on the intended meaning. Even new words are incorporated without disrupting existing knowledge by initially storing them in the hippocampus and gradually integrating them during sleep. This dynamic process ensures we can navigate the ever-evolving world of language efficiently.

Takeaways

• 😀 The average 20-year-old knows between 27,000 and 52,000 different words.
• 😀 By age 60, that number increases to between 35,000 and 56,000 words.
• 😀 Most words spoken out loud last less than a second, requiring the brain to quickly choose the right word.
• 😀 About 98% of the time, the brain successfully picks the correct word.
• 😀 Speech comprehension is different from reading comprehension but shares similarities with sign language comprehension.
• 😀 The brain processes language in parallel, enabling multiple processes to occur simultaneously.
• 😀 Each word we know is represented by a processing unit in the brain, which assesses the likelihood of a match.
• 😀 When hearing a word, multiple neural patterns may become active, narrowing down to one pattern by the end of the word — the 'recognition point.'
• 😀 The brain suppresses other patterns to save time and quickly recognize the word, with a typical comprehension speed of about 8 syllables per second.
• 😀 Context plays a significant role in identifying the intended meaning of words with multiple interpretations, such as homophones or polysemous words.
• 😀 New words are initially stored in the hippocampus to avoid overwriting old ones and later integrated into the brain’s word network during sleep.

Q & A

What is the average number of words known by a 20-year-old?

A 20-year-old knows between 27,000 and 52,000 different words on average.

How does the number of words known change by the age of 60?

By the age of 60, the average number of words known increases to between 35,000 and 56,000.

What is the average duration of spoken words in terms of time?

Spoken words typically last less than a second.

How does the brain select the right word during speech?

The brain makes a quick decision by selecting the word that best matches the signal, with 98% accuracy.

What is the key to our ability to understand speech?

The brain's ability to process multiple tasks simultaneously, known as parallel processing, is key to speech comprehension.

How is each word represented in the brain?

Each word is represented by a separate processing unit, likely a pattern of firing activity across a group of neurons in the brain's cortex.

What is the 'recognition point' in speech processing?

The recognition point is when the brain identifies a word, often well before the word is fully heard, based on the active firing pattern of neurons.

How does context influence word comprehension?

Context helps the brain to narrow down the possible meanings of a word, making recognition faster and more accurate.

What role does the hippocampus play in learning new words?

The hippocampus stores new words initially, keeping them separate from the main word network in the cortex, and helps integrate them gradually over time.

How does the brain integrate new words into the existing vocabulary?

Through a gradual process, new words are integrated into the existing word network during sleep, preventing them from disrupting older words.