engleski

The role of context in Müller-Lyer illusion: The case of negative Müller-Lyer illusion

The Müller-Lyer illusion is one of the most prominent geometrical-optical illusions that have been the subject of experimental investigation throughout a century. Like most optical illusions the Müller-Lyer illusion is caused by an appropriate context - inward or outward fins that act in a specific manner. These fins either prolong or shorten the central line placed between the fins. In this study, we manipulated the context by varying the presentation of the illusion parts, which led to the negative effect of Müller-Lyer illusion. Here we disassociated the context, i.e., the fins that create the illusion, from the lines the length of which needed to be assessed. Firstly, the fins were presented alone for 10 seconds, than the line would appear alone for 100 ms. In such situations the phenomenon of illusion emerges in an opposite direction: the line that temporally succeeded the inward fins seemed longer, while the line succeeding the outward fins seemed shorter. An experiment with three experimental situations was carried out. Twenty participants took part in the experiment, in three different experimental situations. The size of the illusion was measured using the method of constant stimuli, which was also used to determine the point of subjective equality. The analysis confirmed the described effect which was found to be significant when compared to two other situations: the control situation and the standard Müller-Lyer illusion situation. The negative Müller-Lyer illusion is possibly caused by a kind of after effect, which occurred by prolonged gazing at the fins and/or by fatigue of the appropriate selective angle sensitive cells. Such findings implicate that angle sensitive cells might be active in the emergence of the standard Müller-Lyer illusion.

Müller-Lyer illusion; negative Müller-Lyer illusion; temporally disassociated presentation; figural after effect; angle selective cells

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