The rectangle-midline illusion: Effects of attentional processes

In this paper, we present and test the new rectangle-midline illusion by reporting a series of experiments. Participants were asked to move the top or bottom line of an internal-rectangle (and also a single line as a control), which appeared on the computer screen within a big external rectangle, so that the line bisected the external rectangle, dividing it into two equal parts. Deviations from the true midline of the external-rectangle were used to estimate the magnitude of the illusion. The results show that the rectangle-midline illusion increases as a function of the size of the internal-rectangle and its ability to capture attention. The two cognitive processes (TCP) model is proposed to explain the phenomenon, and the findings are compared to previous research in geometric illusions.