Piagetian object permanence and its development in Eurasian jays (Garrulus glandarius)
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Object permanence in Eurasian jays (Garrulus glandarius) was investigated using a complete version of the Uzgiris and Hunt scale 1. Nine hand-raised jays were studied, divided into two groups according to their different developmental stages (experiment 1, older jays: 2–3 months old, n = 4; experiment 2, younger jays: 15 days old, n = 5). In the first experiment, we investigated whether older jays could achieve piagetian stage 6 of object permanence. Tasks were administered in a fixed sequence (1–15) according to the protocols used in other avian species. The aim of the second experiment was to check whether testing very young jays before their development of “neophobia” could influence the achievement times of piagetian stages. Furthermore, in this experiment tasks were administered randomly to investigate whether the jays’ achievement of stage 6 follows a fixed sequence related to the development of specific cognitive abilities. All jays tested in experiments 1 and 2 fully achieved piagetian stage 6 and no “A not B” errors were observed. Performance on visible displacement tasks was better than performance on invisible ones. The results of experiment 2 show that “neophobia” affected the response of jays in terms of achievement times; the older jays in experiment 1 took longer to pass all the tasks when compared with the younger, less neophobic, jays in experiment 2. With regard to the achieving order, jays followed a fixed sequence of acquisition in experiment 2, even if tasks were administered randomly, with the exception of one subject. The results of these experiments support the idea that piagetian stages of cognitive development exist in avian species and that they progress through relatively fixed sequences.
KeywordsObject permanence Piaget Bird Corvid Jay
Experiment 2, younger jays, task 5—search for simply hidden objects, two sites, visible.
Experiment 1, older jays, task 9—search following an invisible displacement, superimposed covers. Birds tried to reach the object as soon as possible by removing more than one screen at the same time. The displacement of the covers was improved using adhesive tape to fix the first and smallest cover onto the bottom of the “cake box”.
Experiment 1, older jays, task 13, search following an invisible displacement, complex complete hiding, invisible.
Experiment 1, older jays, task 14, search following successive invisible displacement, three sites, invisible. The object was visibly placed in the palm of the experimenter’s hand, which was then closed. The hand passed behind two screens (closed) and the object was placed behind the last screen. Then, the experimenter showed his empty hand to the bird.
Experiment 1, older jays, task 15, search following successive invisible displacement. One mealworm was already hidden under the first screen (left side) before beginning the test. Then, a second mealworm was visibly placed in the palm of the experimenter’s hand, which was then closed. The hand passed behind two screens (closed) but the second object was placed inside a glove that the experimenter was wearing on his hand without being seen by the bird. The bird was led to believe that the mealworm was under the third screen (right side). Successful criterion: the jay searched systematically in reverse order, i.e. final screen, second screen and first screen.
Experiment 2, younger jays, Shell game. The experimenter visibly hides an object behind one screen and then the position of the screen is visibly exchanged with one of the other two screens.