Effect of combining Muller-Lyer and horizontal vertical illusions

Abstract

Muller-Lyer (ML) illusion and horizontal-vertical (HV) illusion are two of the most well-known geometrical illusions in simple line drawing. We conducted psychophysical experiments on adult human subjects using geometric shapes consisting of a combination of the components of ML-illusion as well as HV-illusion. Our findings suggest that the arrow (→) or fork (−<) junctions of ML-illusion and inverted 'T' junction (⊥) of HV-illusion continue to have their implicit effects on the perceptual judgement of relative length of two line segments in their vicinity even when the task does not explicitly require our subjects to pay attention to such configurations. Cognitive psychologists have proposed perspective or depth cue based theories to explain these illusions. However, our findings seem to reveal inadequacy of these theories. Hence, we have proposed an alternative model for scene analysis that can be tested and implemented using artificial neural network and computer vision systems.