Benham's Top

The Illusion

Benham’s Top (or Benham’s Disk) is a pattern of black and white arcs that, when spun at the right speed, produces subjective colors known as Fechner colors or pattern-induced flicker colors (PIFCs).

Different people perceive different colors, ranging from faint reds and yellows to distinct greens and blues, depending on the speed of rotation and the individual’s retinal physiology.

How it Works

The mechanism is not fully understood, but it is believed to be caused by the different rates at which our color-sensitive cone cells (Red, Green, and Blue) respond to flickering light.

1. Latency: Different color receptors in the eye have different latency periods (time to activate) and persistence periods (time to fade).
2. Temporal Pattern: The spinning white arcs stimulate the retina in a specific temporal sequence.
3. Neural Confusion: Because the “Blue” cones might react slower than the “Red” cones, the specific timing of the black-to-white transitions activates them out of sync, tricking the brain into perceiving specific hues even though the stimulus is purely monochromatic.

Instructions

• Speed: Adjust the RPM slider. Different speeds trigger different colors.
• Direction: Reversing the spin often reverses the order of the colors (e.g., inside-out vs outside-in).