Thought decoding in the abstract


Brain scans can tell more than we thought about our thoughts and feelings, research suggests.


By Paul Biegler

Researchers have deciphered the abstract concepts people are thinking about – for example justice, truth and forgiveness – merely by analysing their brain scans.








Those airy notions came from the worlds of maths (e.g. probability, multiplication), science (gravity, heat), society (gossip, intimidation), emotion (happiness, anger), law (ethics, crime), metaphysics (causality, necessity) and religion (deity, faith).

The pair then did a painstaking analysis of the scans that combined machine learning with something called multivoxel pattern analysis to look for similarities in the participants' brain responses.

Abstract ideas, it turns out, are less mercurial than we thought.

The researchers were able to nail down the concepts people had in mind just by looking at their brain scans. And they did it with an average accuracy of .82 on a scale where 0.5 is mere chance.


“It is wild to think that my concept of probability and spirituality is neurally similar to the next person's, even if their experience of spirituality is different.”

The two then did a further analysis to map the brain’s representations of abstract concepts at a coarser “category” level.

They found some abstract ideas have social content, essential to forge understanding of things like gossip and intimidation. Other concepts lie on a continuum between the “internal” and “external” worlds, consciousness and gravity for example.

Perhaps most salient, though, is their finding that we tend to represent abstract ideas as words, in contrast to concrete objects which form “percepts” based on how they trigger the five senses.

“[A]bstract concepts both evoke less activation in regions associated with perceptual processing and evoke more activation in regions strongly associated with verbal processing,” the authors write in the journal Cerebral Cortex.

Which raises the prickly question of whether the science of “mind reading” has now advanced to include the abstract.

“It's flashy to call this work mind reading,” says Just.

“For me, it is proof that we have identified some of the elements of the brain's indexing system – verbal representation, externality/internality and the social dimension – that our brains use to code concepts that have no physical manifestation in the world.”

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