Surprise! Even distracted brains can spot irregularities in the environment


In a nutshell: Brains register surprise when they detect something out of the ordinary, no matter how distracted.

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Surprise! Even distracted brains can spot irregularities in the environment

The big picture:

Humans are experts at spotting irregularities. It’s a skill that alerts us to an impending storm, or leads us to the most fruitful tree in the forest, and one that flags with age.

According to this study by CIBF chief investigator Marta Garrido and colleagues at the University of Queensland, our brains subconsciously detect subtle irregularities even when we’re busy doing something else.

Previously, Garrido had people listen to a soundtrack of apparently random tones, that unbeknownst to them obeyed a specific statistical structure, known as normal distribution.

The tones clustered around a central pitch, forming a neat bell-shape when graphed. Every so often, an oddball tone from the edge of the bell was dropped in. Even without trying, participants registered surprise at these high- or low-pitched tones, compared to middle-pitched tones from the centre of the bell.

Surprise responses to the oddball tones were measured using electroencephalography (EEG), which detects changes in the brain’s electrical activity.

In the current study, Garrido’s team measured whether our ability to detect these oddities suffers if our attention is focused elsewhere.

Participants listened to the half-hour soundtrack while simultaneously completing either a simple or a more complex visual task. The complex task required sustained concentration and was demanding enough that participants usually made a number of errors.

But people registered surprise at the oddball tones even when performing the more demanding task.

This is surprising, as our brains are often terrible at multi-tasking — other studies have shown that people usually learn slower and perform worse at simultaneous tasks compared to when the tasks are performed separately.

The brain appears to have made an exception for detecting inconsistencies, because it’s essential to survival, speculates Garrido.

Next steps:
The team will look at whether people are better or worse at detecting statistical outliers when deliberately listening for them.

Garrido, M. I., Teng, C. L. J., Taylor, J. A., Rowe, E. G., and Mattingley, J. B. (2016). Surprise responses in the human brain demonstrate statistical learning under high concurrent cognitive demand. npj Science of Learning, 1, 16006.

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