How our brain processes writing

How the bread works

The challenge of reading writings is too young in evolutionary history for specific areas of the brain to develop for it. But how do we manage to recognize regularities in letter combinations and derive a meaning from them? A new study shows that the basis for this is an evolutionary old mechanism based on recognizing and perceiving recurrent patterns. It did not matter in the experiment whether they were letter-like characters, geometric shapes or varying lattice shapes.

Reading is a challenging task for the brain: it must recognize forms as letters that represent specific sounds in certain combinations and make sense. The first human written languages only developed about 5,000 years ago. However, this period is too short in evolutionary history for our brains to be able to adapt to the new challenge. Unlike, for example, keys or smelling, there is no specially developed reading centre in the brain. So apparently it uses older mechanisms to accomodate.

Words from shapes

A team led by Yamil Vidal from the International School for Advanced Studies (SISSA) in Italy has now investigated the mechanisms involved. To do this, the researchers tested in their subjects how well they recognize recurring patterns in letter combinations – a skill that is considered fundamental when reading. Unlike in classical studies, Vidal and colleagues used not only letter-like characters as stimuli, but also entities that have little in common with letters. The assumption behind this is that “if reading is based on general visual mechanisms, some of the effects that occur when confronted with orthographic signs should also occur when we are exposed to non-orthographic stimuli,” the researchers said. “And that’s exactly what this study showed.”

For the study, the subjects first familiarizes themselves with short “words”, each consisting of three letter-like characters. To prevent participants from being influenced by their prior knowledge, the characters resembled a script but had no meaning. In the next step, participants saw known and new combinations of these pseudo-letters and were asked to identify which of the words were “correct” and which were “wrong”. “We found that participants learned to recognize words in this invented language by how often certain parts appeared together: words that consisted of more common pairs of pseudo-letters were more easily identified,” the authors report.

They repeated the same experiment with three-dimensional objects with three arms, each of which was shaped differently – analogous to the three “letters” in the first experiment. In another test, the researchers used different lattice shapes, which differed by the distance, thickness, contrast, and inclination of the grid lines. From trial to trial, the stimuli became more abstract and dissimilar to real letters. Nevertheless, the subjects were also able to distinguish suitable and inappropriate stimuli in these experiments.

Regularities in words and faces

“What emerged from this study,” the authors explain, “not only supports our hypothesis, but also tells us a little more about the way we learn. It suggests that a fundamental part of this is the recognition of statistical regularities in the visual stimuli that we perceive around us”. Thus, we observe what surrounds us, subconsciously break it down into elements and intuitively analyze their frequency. Responsible for this is the left fusiform gyrus in the brain, a part of the cerebral cortex.

Previous studies have shown that this region is active both in reading and in recognizing objects, especially faces. According to the researchers, this evolutionary old ability is “recycled” when humans become capable of reading. In all cases, it is crucial to recognise regularities and give them meaning. “In short, there is an adaptive setting to stimuli that occur regularly. This finding is important not only to understand how our brains work, but also to improve artificial intelligence systems that base their learning on the same statistical principles,” the researchers said.