Figure 1. A & B. Basic configurations.

A) basic task configuration for acquisition & transfer test 1, 3 and 4. L5) pin; L4) screw; L3) bolt; L2) wheel; L1) bar. The pin is inserted through a perforation in the screw end; the screw is held by a fixed nut and blocks the upward movement of the bolt; a protrusion in the bolt’s end fits into a recess on the wheel’s edge, blocking its rotation; the wheel impedes the displacement of the bar, which blocks the window behind which is the food. To be removed, the wheel has to be rotated to align its central slot to the T-bar passing through its axis.

B) configuration for TT 2. The position of all locks except ‘bar’ has been altered (a recess in the screw matched the bolt’s protrusion, and a passing hole through the bolt let the pin go through so that the pin had to be removed for the bolt to be lifted).