fig 1.

Example of the Tower of London screen.

A, Sample screen of one of the configurations of a planning problem. Upper, baseline configuration; lower, target configuration. In this example, the participant has been asked to move first the blue ball to the right rod, which is counterintuitive. Thereafter, the participant has to place the yellow ball on top of the red ball, the blue ball at its destination, the yellow ball on top of the blue ball, the red ball on the right rod, and, finally, the yellow ball at the target position (sixth move). Two alternatives are presented on each side of the screen, from which the participant had to choose the correct answer. The participant was asked to respond by pressing the air bulb at the corresponding side.

B, Sample screen of the control configuration. The participant has to count the yellow and blue balls altogether. In this example, the answer is six, which is indicated on the right.