Figure 1.
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).
Figure 2.
Actions required for removing each individual lock (L1-L5).
Figure 3.
In TT1 and TT3 one or two locks were removed; in TT2 both configuration and order of tasks were changed as well as removing one or no locks. In TT4 either the wheel (WNF) or the screw (SNF) were non-functional but their edges were still touching the lower and upper locks (2x or 4x = no. of times each condition was presented in each session of ten trials). Subjects received two sessions of TT1 and TT2 and one session of TT3 and TT4. Correct behaviour was scored when the bird touched and removed first the lock marked green.
Figure 4.
Mean percentage of time it took the animals to remove each lock.
The mean percentage of time it took the animals to remove each lock was measured between completion of successive steps. Data from first 20 successful removals during acquisition phase (locks represented by the coloured lines; dashed line represents average across locks; Times are standardized so that first removal of each lock is 100%).
Figure 5.
A-C. Mean number of correct choices in the transfer tasks.
The mean number of correct choices in the transfer tasks (first lock touched out of four trials) and chance expectation are given for each of the conditions in the transfer tests (locks missing or non-functional); A) TT1 (black) and TT2 (grey) B) TT3; C) TT4. * Number of correct choices differed significantly from chance (two tailed).