Grey crows manipulate objects according to a mental pattern until new circumstances force them to change their behavior.
Many animals use tools, but few know how to make them. And if we talk specifically about making tools, then, in addition to the great apes, there are two outstanding examples – New Caledonian crows and Goffin’s cockatoos. We have written about both of them many times: cockatoos, for example, treat their tools with care, like real craftsmen, and can use not just one tool, but a whole set. Crows can make the same tools not just one way, but in different ways, and they are capable, if necessary, of assembling one large tool from several smaller parts.
New Caledonian crows differ from cockatoos in that crows have been observed making tools in the wild, while cockatoos have only made them in experimental conditions. Moreover, crows in the wild use three types of tools: straight sticks, hooks, and bayonets. Bayonets differ in different bird populations, and these differences are maintained from generation to generation, which partly resembles a cultural tradition. On the one hand, the features of tools can be reproduced simply through learning: a young bird watches what an old one does and repeats its actions. On the other hand, crows can form an internal representation of what a tool should look like, after which it remains, so to speak, to translate this mental template into reality. One does not interfere with the other: in the first case, the consolidation of the type of tool occurs through interaction between birds, in the second case, everything happens in the psyche of the same individual, which once learned to make a tool and now always turns to its previous experience. What is important here is that the bird refers to the mental template until it is forced to do the opposite, until there is an obvious need to change something.
Both New Caledonian crows and Goffin’s cockatoos have been tested and found to follow a mental template – that is, they make tools based on the requirements they have encountered in the past. Researchers from Moscow State University and the University of Bristol wanted to see if common hooded crows have this ability. Hooded crows do not make tools in the wild, but like many corvids, they have outstanding cognitive abilities. Three hooded crows were trained to insert small pieces of paper into a gap in a screen. For each piece of paper inserted correctly, they received a treat – a mealworm larva. (It would be a stretch to call these pieces of paper “disposable tools.”) The next step was to see if the crows could tear off pieces of paper themselves that could be placed in the gap if they were given an A4 sheet of paper. All three crows figured out the correct action: they tore the paper and stuffed it into the crack, without any additional training.
Then they were taught to choose only the blue ones from four blue and four yellow pieces of paper, and after the training they were given a large sheet of paper again – or rather, two sheets, blue and yellow. Here they were also given a treat, but the treat was, so to speak, random: it was given only in half of the test trials and regardless of which piece of paper the crows put in the crack, yellow or blue. This was done so that the crows would not think of retraining, so that they would not develop a new connection between the treat and the color of the pieces of paper they were supposed to tear off. And in this situation the crows tore off pieces from the blue sheet – just as they had done quite recently.
Then the crows were taught to distinguish between large and small paper rectangles – they had to put rectangles of a certain size into the gap again. The “test”, as in previous times, consisted of learning to independently tear the paper into the necessary rectangles. But after this, the experimental crows were retrained to make rectangles of a different size. Retraining affected their behavior: if a crow had previously made small triangles, now it was taught to make large ones – and it began to make large ones; and vice versa.
It seems natural to us to remember what and how we did in the past and not to change our behavior without serious reasons. But this actually requires remarkable mental abilities: when faced with a similar task, you must remember what you did before and evaluate the new conditions – whether it is necessary to change something for them or not. Grey crows, when the new conditions were random and incomprehensible, manipulated the paper in accordance with the mental template – that is, remembering what they were taught before (experiment with colored papers). When the conditions still noticeably inclined to new solutions (experiment with different-sized rectangles), the crows quickly learned the new solutions. Here we must not forget that such manipulations of environmental objects are not some kind of species-specific behavior for grey crows. It can be expected that other birds with a developed brain demonstrate similar memorability and, at the same time, cognitive plasticity.
The results of the experiments are described in Animal Cognition. The work was supported by the Russian Science Foundation.
Based on materials from the press service of Moscow State University.
Source: www.nkj.ru
