In Chapter 6, we said that researchers have used the modern understanding of human visual processing and the visual cortex to come up with new optical illusions — illusions that could not have been produced fifty years ago, except by unlikely accident. Below, we cite a few representative examples.

The “curvature blindness” illusion has some grounding in the general phenomenon of curve blindness, but this specific illusion was carefully constructed from first principles circa 2017, as opposed to being discovered by accident. (Original study)

In 2022, Bruno Laeng and collaborators published a study in which they demonstrated that their new “expanding black hole” illusion actually caused participants’ pupils to expand, as if in anticipation of entering a dark space. (This effect was noticeably larger than the effect of merely focusing on a darker visual target, which would also cause the pupils to expand by a small amount.)

The “Scintillating Starburst” illusion, revealed in 2021, was carefully built atop work on luminance and illusory contours going back to the late 1970s.

The “Pinna-Brelstaff” illusion, developed circa 2000, is less of a central example of building a new illusion based on understanding human biology. Still, it’s interesting and relevant from a different angle in that it is an illusion based on novel technology, i.e., one that would have been difficult or impossible to create without modern computers.

Also less centrally, the “Eclipse of Titan” illusion, created circa 2010, exhausts the viewer’s M cones, allowing the less-exhausted L cones to create the perception of a brilliant blue that would otherwise have been moderated and weakened by simultaneous M and L activation. (More detail.)

Relatedly, the study of cone activation in the early 2000s led to the creation of various chimerical colors, via careful manipulation of cone activations unlikely to occur in nature.^*

Finally, some ongoing experiments show that:

Rhythmic waves of brain activity cause us to see or not see complex images that flash before our eyes. An image can become practically invisible if it flashes before our eyes at the same time as a low point of those brain waves. We can reset that brain wave rhythm with a simple voluntary action, like choosing to push a button.

…further demonstrating that a richer understanding of biology and physiology allows for a greater range of strategic motion. Here, perceptions can be altered in ways that don’t depend on changing the sensory input to the optic nerve at all, but instead simply depend on timing the arrival of stimuli to sync up with other things happening in the brain.