Inaccurate feedback and performance on the Müller-Lyer illusion.

The effects of accurate and erroneous feedback on magnitude of illusion for the Müller-Lyer illusion were examined. The provision of accurate feedback substantially reduced the magnitude of the Müller-Lyer illusion whereas the influences of inaccurate feedback were dependent upon whether subjects were prompted to overestimate or to underestimate the length of the comparison line.