Hearing Illusions: Why Kick is What We Hear When Pick Is What Was Told?

Speech's incorrect perception is often related to a weak representation of the difference between what we expect to hear and what is actually said, finds a new study. The findings of this study are published in the Journal of Neuroscience.

The ability to draw on past experience is important to keep up with a conversation, especially in noisy environments where speech sounds are hard to hear. However, these prior expectations can sometimes mislead listeners; convincing them that they heard something that a speaker did not actually say.

‘New evidence with regard to hearing illusions has been found. The human brain tends to create perceptual illusions when speech is degraded at cocktail parties or in song lyrics.’

To investigate the neural underpinnings of speech misperception, Helen Blank, Matt Davis, and colleagues presented participants with pairs of written and degraded spoken words that were either identical, clearly different or similar-sounding. Reading and hearing similar sounding words (like kick followed by pick), led to frequent misperception.

Using functional magnetic resonance imaging, the researchers found that misperception was associated with reduced activity in the left superior temporal sulcus, a brain region critical for processing speech sounds. Furthermore, when the perception of speech was more successful, this brain region represented the difference between prior expectations and heard speech (like the first k/p in kick-pick).

These results provide new evidence that speech perception involves comparing what we hear with what we expect. This mechanism -- predictive coding -- has implications for treating age-related hearing loss or understanding auditory hallucinations in disorders such as schizophrenia.

Source: Eurekalert