A Chocolate Heist: Neuroscience of Dark Adaptation

When you step from a lit room into a dark one — perhaps to nab some nighttime chocolate — you might struggle to spot the light switch. But if you pause for a few minutes, you’ll notice your vision slowly begin to improve. This phenomenon relies on two nerve cells in our retinas: cones and rods. Cones help us see colors clearly in well-lit environments, while rods are optimized for seeing black and white in low-lit ones.

Rods produce a protein called rhodopsin, which depletes in settings with a lot of light to prevent your eyes from becoming overstimulated. In the dark, however, rhodopsin production rachets up over time. This process sharpens your low-light vision — but it can’t offer the same level of detail cones do in bright light. The brain also helps adjust the sensitivity of our vision in a process called contrast gain control, fine-tuning our sight to better spot the chocolate in the dark.

Created by Christoph Koenig.