Why Do We Look Slimmer In Black Clothes?

According to SAEDNEWS, The world of fashion has many rules. Although many of these rules are old, conventional, or even incorrect, one rule always remains beyond traditions and within the realm of neuroscience: black clothes make you look thinner. The reason is not that black clothing actually makes us thinner, but rather how the visual system processes light.

Surely no one expects a fashion article to begin with a physicist. However, this is not a simple text. Hermann von Helmholtz wrote a book called “Handbook of Physiological Optics,” in which he explained in detail the influence of physics, physiology, and psychology on what we see, and discussed optical illusions that explain why we perceive things the way we do.

Look at the image below. Helmholtz called this effect the radiating illusion. The holes in both shapes are the same size, but the white one appears larger than the black one.

Which hole is larger?

This phenomenon is exactly what makes you appear slimmer in black clothes. But why does this happen?

In 2014, researchers placed electrodes on the visual areas of cats, monkeys, and humans to record neural signals. Participants (animals and humans) were shown white shapes on a black background and vice versa.

The recorded neural signals showed that the visual system works in two ways: “ON” neurons, which respond to light, and “OFF” neurons, which process darkness.

OFF neurons respond to dark shapes on light backgrounds, and the greater the contrast, the more active they become. Reversing the contrast shows that ON neurons respond strongly to light shapes on dark backgrounds.

This makes sense because in the dark, humans need to detect any available light sources, and historically there was no constant artificial lighting. Therefore, the brain evolved to perceive bright objects on dark backgrounds as larger than they actually are. However, detecting dark objects in daylight is easier, so no such evolutionary enhancement developed for them.