Colour me confused
In this illusion, we’re shown grey bubbles of different sizes then four colourful bubbles of the same size in a bullseye formation.
The video prompts us to stare at a cross at the centre of the screen, and when the bubbles alternate, the grey circles are instead filled with a soft colour matching one of the colours in the bullseye.
The bullseyes leave an afterimage; a leftover, persisting “impression” in the retina, making us see things that aren’t really there.
The illusion was produced by Mark Vergeer, Stuart Anstis and Rob van Lier from the University of Leuven in Belgium and Radboud University Nijmegen in the Netherlands.
One to make your head spin
Sylvia Wenmackers from the University of Belgium came across this illusion when she saw the silhouette of windmills against the clouds looking as though they were spinning in opposite directions.
But she was actually seeing one of the windmills from a back-angle, which created the illusion that it was spinning counter-clockwise.
The model in the video shows the windmills as a silhouette, then in a daylight setting. In daylight, the real direction is clear.
Here, the notion of contrast creates the illusion. Jose Manuel Alonso from State University of New York uses light and dark greyscale colours on the pixels that make a woman’s face.
The colours we see depend on the other colours surrounding it, known as “lateral inhibition”, which is the tool your brain uses to make edges and ultimately create the illusions.
He shows us two photos of the same woman, each with either the light or dark pixels set to grey while keeping everything else unchanged.
We compare the whites of the woman’s eyes in the light photo with her lips in the dark photo. They look significantly different, but when he enlarges and overlaps the pixels from each, we find they’re exactly the same colour.
Rows of blocks sit in front of a mirror, but it reflects a different shape back to us: circles or rectangles.
Kokichi Sugihara from Meiji University in Japan finds the illusion doesn’t go away, even though we know the blocks haven’t changed.
This illusion depends on the shape of the blocks and the angle we see them. The “true” shape is actually mid-way between a circle and a square with dipped edges.
For the remaining finalists and winner, check out the Best Illusion of the Year site. The contest is run annually by the non-profit Neural Correlate Society.
Anthea Batsakis is a freelance journalist in Melbourne, Australia.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.