A new study from Duke University revises our idea of how the visual system works.
Old idea: bottom up
According to the older idea, images are constructed in our minds in a hierarchical fashion starting at the bottom. Data arriving at the retina is sorted into basic features, such as horizontal and vertical lines. These elements gradually resolve as they pass up through the layers of neural organization. Eventually they form into complete images that we recognize as particular objects. The brain’s higher level inferences, according to this model, develop only after this bottom-up process is completed.
New idea: top-down
Experiments using modern brain imaging data show that the process is really quite the reverse. The new idea, called “predictive coding,” proposes that the brain develops predictions about what we’re about to see. It tests those predictions in a top-down, rather than merely a bottom-up mode. The information that we take in is edited to fit the conception. This all happens within milliseconds and is largely unconscious.
Whenever low-level input contradicts the predictions and forces us to change our reading of an object, there is a storm of neural activity. This neural storm is particularly strong with optical illusions, such as the one that began this post. You may have experienced this if you ever, in a split second, mistook a stick on the ground for a snake. The top-down expectations get quickly overwhelmed by bottom-up corrections.
This illustration from Dinotopia: The World Beneath shows this kind mental process in action. An ambiguous cave formation, left, can either be seen as a skull or a woman with babies. Depending on how the mind wants to perceive the form, the details are marshaled to match the perception.
This phenomenon of conjuring faces and other meaningful patterns in apparently random visual data is a phenomenon that’s also called “pareidolia,” covered in an earlier post.
Here are three suggestions for how this new theory may affect us as artists (and I'm sure you'll think of other implications:
1. We mostly see what we expect to see. Viewers come to your pictures unconsciously preloaded in various ways.
2. Much information is lost because of this automatic editing process. It never reaches our conscious minds because it's edited out. Therefore we just don’t see a huge amount (and maybe that’s a good thing at times).
3. Having a wrong search image can actually make us blind to what we’re looking for. For example, if you thought the book you were looking for had a blue spine, you might not even see the correct book with the red spine.
Duke University news release
Another report on predictive coding
First optical illusion from Planet Perplex
Related GJ Post on Pareidolia and Apophenia:
Thanks, Rob Wood and Brad