The Solution of Patterned String Problems By Birds

Abstract

1. Three budgerigars quickly learned to pull to their cage a 15 cm long black string to which a small food container was attached. Then two strings of the same length but of different colour were offered, one of which was cosmected with a food container. One budgerigar learned successively with significant percentages of correct choices to pull the string with the container when both strings were arranged in one of 7 different patterns (Fig. 2 A-G). The bird mastered 2 of these arrangements spontaneously. Finally the budgerigar chose correctly in significant percentages of choices when 4 of these tasks were offered in predetermined irregular sequence in series of 30 trials. In these cases also the colours of the strings, the position of the correct string to the right or to the left, and the normal or the reflected arrangement changed in predetermined, irregular succession. These continuously changing situations always required different associative processes and new decisions. A second budgerigar mastered such tasks only when not more than string patterns were offered in irregular sequence. A third budgerigar learned to choose the correct string only when one of the simple string patterns A, B or C was offered in a series of trials. An Indian starling (Acridotheres tristis) and a jackdaw (Coloeus monedula) quickly learned to pull a string with a food container, but proved to be inappropriate for experiments with two strings because the handling of the strings in itself appeared rewarding to them. 2. The results of these experiments confirm that the brain achievements of birds are not inferior to those of mammals, although their forebrain lacks a cortex with several layers of neurons. They support the hypothesis that the specific configuration of forebrain regions is less important for more difficult brain achievements than the number and differentiation of neurons and the number of synapses.