[Evaluation of the ability to solve the Revecz-Krushinskiĭ test in corvine birds]

Reasoning ability in crows was investigated by means of the Revecz-Krushinskiĭ test, in which the bird has to apprehend the rule of stimulus (food bait) displacement: "In each next trial the food bait is hidden in a new place--one step further along the row". By means of computer modelling the criteria of statistical evaluation of this problem solving were established. The test was considered solved when the number of trials which preceded the detection of food was less than those which were calculated for chance performance. High level of reasoning ability in crows is discussed.