Which illusion results in people perceiving two lines of the same length as different lengths?

The Ponzo illusion is a perceptual phenomenon where two parallel lines are perceived to be of different lengths due to the context provided by surrounding visual elements. Specifically, in this illusion, the lines appear on a background that creates a sense of perspective, similar to how railway tracks converge in the distance. As a result, the upper line appears longer than the lower line, even though they are actually the same length. The brain interprets these lines based on the visual cues of depth and distance, leading to the misperception.

The other illusions listed create different effects based on various visual manipulations, but they do not primarily rely on perspective cues to create the perception of differing line lengths. Each illusion works through different cognitive biases and principles of visual processing that do not involve this specific contextual influence.