Visual illusion
Biological Motion Illusion
A demonstration of the Johansson point-light walker phenomenon, showing how 15 moving dots creates a vivid perception of a human figure.
The Phenomenon
Biological motion perception is the brain’s ability to identify biological entities from their movement patterns alone. In 1973, Gunnar Johansson demonstrated that just a few points of light attached to the joints of a moving person are sufficient for observers to instantly recognize a human figure, identify its gender, and even determine its mood.
The Demo
This interactive visualization approximates the kinematic motion of a human walker.
- Speed: Controls the gait cycle speed.
- Scramble: Randomly offsets the dots while keeping their local motion vectors, testing how spatial structure affects recognition.
- Noise Dots: Adds random moving dots (“masking”) to test the robustness of the signal detection.
- Invert: Flips the walker upside down. Research shows that biological motion perception is orientation-specific; an upside-down walker is much harder to recognize.
References
Johansson, G. (1973). Visual perception of biological motion and a model for its analysis. Perception & Psychophysics, 14(2), 201-211.