There’s a seemingly unending number of optical illusions that play on the limitations, and the tendencies, of our visual systems. Let’s explore a few more.
In the above image, the blakc heart looks like it’s constantly expanding! However, it never seems to get bigger, and it’s not a looped gif, so what’s going on?
This illusion plays on the fact that our eyes are constantly moving (if you don’t believe us, ask someone to track your eye movements for a bit.)
If we simply saw everything in real time, since our eyes constantly move, we’d have a hard time seeing anything comprehensible. To compensate for this, the brain “edits” all this compiled input into an image we can properly see, similar to how a good movie editor can seamlessly edit scenes together. Our brains also rely on the context of an object to effectively determine what it sees.
In the illusion here, the lined background is used by the brain as a reference point to orient the heart. Between the lines, and our eyes’ constant movement, the heart thus appears to be expanding.
Another image that provides the illusion of movement, the spirals above appear to be slowly spinning by taking advantage of a phenomena known as apparent motion.
It takes one tenth of a second for signals from the retina to reach the brain, and if there is more contrast in what the brain is seeing, the faster the transmission. (For example, a higher contrast signal arrives one twentieth of a second faster than a low-contrast one.) So in this illusion, the contrast gradients are arranged in a way that tricks the brain into believing there is motion, as the high contrast parts of the image arrive faster than the rest.
There are several different images that illustrate this phenomenon, but they all fall into the same general group of impossible shapes. The image depicts an object which, at first glance, appears realistic, but upon closer inspection, its mind twisting nature becomes clear as we realize that this shape could never exist in a real, 3D form.
This illusion is related to the Gestalt laws, which describe how we see and interpret the world around us, with everything being parts of a single image. So we see, in complex scenes, objects against a background, and those objects themselves are made of parts, which in turn are made of smaller parts.
According to one of these Gestalt laws, when we see ambiguous or complex objects, the brain tries to make them look as simple as it can. That is why our brain tries to ignore the impossibility of this shape, enabling us to process the image, and once we force it to acknowledge the impossibility of the shape, it becomes an eye-twisting anomaly.
There is always more to be learned about the visual system, and illusions like these always demonstrate that what we see might not always be what’s actually in front of us.