How good is YOUR colour perception? Deceptively difficult test tasks you with finding the boundary between two shades – so, how far can you get?
How good is YOUR colour perception? Deceptively difficult test tasks you with finding the boundary between two shades – so, how far can you get?
A novel challenge has emerged that pushes the boundaries of our understanding of colour recognition. This test, known as ‘What’s My JND?’, presents users with a seemingly simple task: identifying the dividing line between two adjacent hues. However, as the game advances, the shades grow increasingly indistinguishable, making the task far more complex than it initially appears.
The game’s mechanism
Players are shown two color blocks on the screen and must click the line separating them. While the task sounds straightforward, the difficulty escalates rapidly. The initial rounds feature starkly different colors—such as grey and blue or brown and orange—but later stages reduce the contrast to the point where the distinction becomes nearly imperceptible.
‘You see two colours. Click on the line between them. That’s it. It starts easy. It does not stay easy,’ the game’s instructions explain.
The test typically spans 40 rounds, with participants aiming to detect the smallest perceptible shift in color. On average, users score around 0.02, a figure that highlights the precision required to succeed.
Behind the design
The test was developed by software engineer Keith Cirkel, who sought to explore how accurately humans can perceive color on digital displays. By measuring the ‘Just Noticeable Difference’ (JND), the game assesses the threshold at which color changes become detectable to the human eye.
To begin, visit the game’s website and tap the ‘Let’s go’ button. Each round, two color blocks appear, and your goal is to locate the boundary. After each attempt, you’ll receive immediate feedback on whether your guess was correct or off the mark.
User experiences
‘Rough. But look, I once failed a colour vision test because the room had fluorescent lighting. Environment matters. Try again in a dark room with your brightness cranked. Or don’t. I’m not your mum,’ one player noted when struggling with the test.
For those who master the test, a harder version is available. In Hard Mode, nine squares are displayed—eight identical in color and one subtly different. The objective remains the same: spot the odd one out.
‘Genuinely remarkable. You sailed past the theoretical human limit like it owed you money. I’d accuse you of cheating but I don’t actually how you’d cheat at this,’ a message appeared for high scorers.
Players have shared their results on social platforms, sparking discussions. One user remarked, ‘This is great fun. How good is your colour perception? What are the finest shades you can distinguish? Apparently I’m a bit special.’ Another added, ‘Some were just completely uniform to me. I had no idea. Had to keep tilting my screen all ways to try to spot a border but still ended up guessing.’ A third joked, ‘Not bad considering I’m colourblind.’
Science of color vision
Humans and other creatures rely on intricate eye structures to process color. The pupil adjusts light intake, functioning similarly to a camera lens. Both cones and rods, types of photoreceptors in the retina, play roles in vision. Rods detect low-light levels, enabling grey-scale perception, while cones specialize in color recognition.
Most species, including humans, possess three cone types, each responding to different light wavelengths. This trio allows the full spectrum of visible colors—from red to blue, which span 390 to 700 nanometers—to be perceived. However, certain animals, such as many birds, have four cones due to a condition called tetrachromacy. This adaptation lets them detect ultraviolet light, expanding their visual range beyond what humans can see.
When light hits these photoreceptors, it triggers electrical signals as the cells change shape. These signals travel through the optic nerve to the brain, where they are integrated at the optic chiasm. This region compares the two visual inputs, enabling us to perceive the world in color and detail.
Key facts
Players typically complete the test in 40 rounds. The average score is 0.02. Keith Cirkel designed the test to investigate the precision of color perception on screens. The game is available online and includes a harder variant for those seeking greater challenge.
