Abstract
For the most part, we talk because we want to communicate with others: our friends, parents, teachers, even pets. Our voice carries our message to other people's ears. However, they are not the only one listening: when we talk, we can hear ourselves with our own ears as well. Do we pay attention to the sound of our own speech? Listening to what we say would be very useful, because we could listen for mistakes in our speech and make sure that we fix them so the right message gets across. How does our brain react when we hear ourselves make a mistake while talking?
When We Talk, Who is Listening?
We did an experiment to figure out what happens when we hear ourselves make a slip of the tongue – we will call it a speech error
However, it is difficult to study real speech errors, because you have to wait for them to happen. So here is the trick: we fooled the participants into thinking they had made an error. Most of the time during the experiment, they heard their own voices normally, but occasionally, they said one thing and heard another. How did the trick work? First, we took the words that were picked up by the microphone, and we used a computer to change the way the words sounded. We changed the vowel (A, E, I, O, U) and left the rest of the word as it was. Then, we played the new changed sound to their headphones (see Figure 1 for an illustration and sound clips). For example, if a participant said “bed,” they might have heard “bad” come back through the headphones. With fast computers, we can record, change, and play back the words extremely quickly (seventeen thousandths of a second!). It sounds so natural that many participants did not even notice that anything out-of-the-ordinary had happened.

- Figure 1
- Diagram of a normal word production (left) and the one that has been altered to sound like an error (right).
The Brain Listens for Errors
Even though most of the participants could not consciously tell that their speech had been changed, their brains noticed the difference! The auditory cortex

- Figure 2
- Brain areas that are more active during “errors” than during normal speaking.
What is this Increased Activation Doing?
It turns out that the more your auditory cortex is active, the more you change the way you are talking to fix your “mistakes,” undoing the changes that the computer applies. For example, let us say we asked the participants in the experiment to say the word “bed.” All spoken words are made up of frequencies
We Can Correct Our Speech without Even Knowing it
Sometimes, we notice that something we said did not sound quite right, and we correct ourselves (“oops, what I meant was.”). In this study, we showed that people can correct an error in their speech even before they have finished saying the word, without ever even noticing that they are doing it. This suggests that, in day-to-day conversations, we can automatically correct ourselves to fix mistakes as they are happening.
We also showed that the auditory cortex becomes more active during these errors, and that people with stronger activity in this area did a better job correcting the errors. Therefore, identifying and fixing these speech errors happens with the help of the auditory cortex. Our brains probably use this automatic error-correction process all the time as we speak, keeping us on track and saving us from a lot of mistakes. Think about that the next time you hear a slip of the tongue!
Glossary
Auditory cortex ↑ The part of the brain that processes sound.
Frequency ↑ A property of sound that we can use to tell apart different notes of a song, different voices, and different vowels.
Speech error ↑ Saying one thing when you mean to say something else.
References
[1] ↑ Niziolek, C. A., and Guenther, F. H. 2013. Vowel category boundaries enhance cortical and behavioral responses to speech feedback alterations. J. Neurosci. 33:12090–8. doi:10.1523/JNEUROSCI.2137-13.2013
[2] ↑ Tourville, J. A., Reilly, K. J., and Guenther, F. H. 2008. Neural mechanisms underlying auditory feedback control of speech. Neuroimage 39:1429–43. doi:10.1016/j.neuroimage.2007.09.054
[3] ↑ Purcell, D. W., and Munhall, K. G. 2006. Compensation following real-time manipulation of formants in isolated vowels. J. Acoust. Soc. Am. 119:2288–97. doi:10.1121/1.2173514
[4] ↑ Cai, S., Ghosh, S. S., Guenther, F. H., and Perkell, J. S. 2011. Focal manipulations of formant trajectories reveal a role of auditory feedback in the online control of both within-syllable and between-syllable speech timing. J. Neurosci. 31:16483–90. doi:10.1523/JNEUROSCI.3653-11.2011