New research from the Cultural Brain Lab indicates that literacy does not impact the perception of visual shape and color illusions. The findings provide evidence that people are affected by optical illusion regardless of their ability to read and write.
The study has been published in the Journal of Cultural Cognitive Science.
“Learning to read has a profound impact on people’s lives, changing not just their socioeconomic perspectives, but how they relate to the world,” said lead researcher Falk Huettig, a senior investigator at the Max Planck Institute for Psycholinguistics and a professor of psycholinguistics and cultural cognition at Radboud University.
“The broad significance of literacy has led researchers to investigate the cognitive and neural processes that underlie the acquisition of this evolutionarily very recent culturally-transmitted skill. Learning to read and write improves verbal memory, phonological awareness, prediction during spoken language processing and even the perception of facial emotions and non-verbal intelligence.”
“In our previous research with illiterate and literate people in India, we found that reading ability leads to better mirror image discrimination and face recognition abilities. We therefore decided to investigate previous claims by Russian scholars that illiterate individuals are unable to perceive visual illusions. Given the above effects of literacy, it was conceivable that illiterate people would show such difficulties, but on the other hand we were skeptical because there was no good explanation how such an effect could come about.”
For their study, the researchers conducted controlled experiments with adults of varying literacy levels in Chennai, India. The sample included 66 participants who did not know how to read and write, 62 highly literate participants who had completed at least 10 years of formal education, and 30 low literate participants who only completed primary education and dropped out during middle school. The participants were carefully matched in socioeconomic status.
The participants were shown 16 shape illusions and 6 color illusions, and orally asked a yes or no question about each image. For example, one of the images depicted the Müller-Lyer Illusion in which a horizontal line with arrowheads looks shorter than a horizontal line with arrowtails. The participants were shown the image and then asked: “Are the two horizontal lines of the same length?” The participants also viewed 22 control images, which were created by removing the visual factors causing the illusions.
The researchers found no evidence that literacy had an impact on the perception of the visual illusions.
“Our large sample, carefully controlled study strongly suggests that literacy does not meaningfully affect the identification of visual illusions. Learning to read substantially changes some visual perceptual processes such as mirror image processing and face recognition but the perception of visual illusions does not appear to belong to the class of visual processes that can be altered by this recent human cultural invention,” Huettig told PsyPost.
“Our findings raise some questions about other reports about cultural effects on illusion perception,” he added. “Some other research found that children and adults from a range of human societies across the world showed differences in their susceptibility to different illusions. Hunter-gatherer societies such as the San people of the Kalahari Desert, for example, were found not to be susceptible to some visual illusions.”
“Our study looked at the effect of literacy and not the effect of culture on the perception of visual illusions. Our results do however suggest that researchers should have another careful look at these older studies and investigate whether those results replicate.”
The study, “Do illiterates have illusions? A conceptual (non)replication of Luria (1976)“, was authored by Mrudula Arunkumar, Jeroen van Paridon, Markus Ostarek, and Falk Huettig.
