Selective looking and the Müller-Lyer illusion: the effect of changes in the focus of attention on the Müller-Lyer illusion.

According to a selective looking paradigm subjects were required to attend to the inward-going or outward-going components of a combined Müller-Lyer figure in which both components were present and distinguishable by colour. The amount of the illusion was found to vary according to which component the subject attended. Subsidiary findings relate the amount of the illusion to fin angle, fin length, and length of shaft.