Hearing people mix up tenses within a sentence, use a double negative or confuse the singular and plural can really get on the nerves of many. Now, researchers from the University of Birmingham have finally proven that hearing people use bad grammar can cause a physical reaction. This reaction even affects our heart rate.

The relationship between language cognition and physiology is often studied in different ways. The new study brings into focus a new dimension of the relationship between the two.

It all boils down to our stress reactions. The autonomic nervous system (ANS) controls our heart rate. In particular, researchers looked at the heart rate variability (HRV) of people listening to incorrect grammar.

Stressful grammar

HRV indicates the length of time between successive heartbeats. It’s an indicator of the heart’s ability to respond to different stimuli, including stressors. By keeping track of HRV, researchers can gain insights into participants’ stress levels.

For their study, the researchers recruited 41 British-English-speaking adults and asked them to listen to 40 English speech samples — half of which contained grammatical errors in the form of articles, such as omitting a “the” or adding an “a/an” when it wasn’t needed. They recorded the participant’s HRV as they listened to the sound clips.

As the number of errors in speech increased, individuals experienced a parallel increase in the regularity of their heartbeats, associated with elevated stress levels, the researchers found. “Cognitive effort reverberates through the physiological system in more ways than previously thought,” Dagmar Divjak, study author, said in a news release.

This finding doesn’t only apply to bad grammar — it could help us better understand our cognitive processes and how the nervous system directs them.

The ANS has two main elements, the sympathetic and the parasympathetic nervous system (SNS and PNS respectively). The first one activates a “fight or flight” response to a threat, while the second one controls the “rest and digest” and “feed and breed” functions of our body. The study shows that the PNS, too, responds to cognitive demands. Cognitive demands refer to the mental processes and tasks that require attention, thought, and effort.

“Your knowledge about your first language is largely implicit, i.e., learning your mother tongue did not require you to sit and study, and using it does not require much, if any, thought. This also means that you will find it hard to pin down what exactly is right or wrong about a sentence and, even worse, explain why that is so,” Divjack said.

Nevertheless, the precise evaluation of an individual’s linguistic skills remains vital, irrespective of their age, physical condition, or cognitive capabilities, for questions related to core areas of life relating to cognition, Divjack argued. This study then gives researchers a new way to look into aspects of cognition that aren’t directly observable.

The study was published in the Journal of Neurolinguistics.