ИСТИНА

A two-alternative simultaneous matching-to-sample task was used. Previously, after extensive training, the two crows acquired the general identity matching-to-sample rule. Experiment 1 and Experiment 2 used numerosities 1-4 and 5-8 correspondingly. Each experiment first included the demonstration trials and then the test trials. In the demonstration trials a sample and the comparison stimuli belonged to the same category: heterogeneous graphic arrays or Arabic numbers (identity matching trials). After making a correct choice, the birds found the number of mealworms that was the same as the number of elements in the array, or as the Arabic number. In the test trials a sample and the comparison stimuli were from different categories: if a sample was an Arabic number, the comparison stimuli were arrays, and vice versa. The test trials with non-differential reinforcement were intermixed with identity matching trials from the demonstrative set (one test trial after three identity trials). Each experiment included two tests: Test 1 with the familiar pictured arrays and Test 2 with the new one. In the Experiment 1, in the Test 1 the crows made 33 and 36 correct choices over 48 trials (p<0.01); in the Test 2 the crows made 34 and 37 correct choices over 48 trials (p<0.001). In the Experiment 2, in the Test 1 one of the two crows made 39 correct choices over 48 trials (p<0.0001); and in the Test 2 crow made 41 correct choices over 48 trials (p<0.0001). These results demonstrated that the crows were able to spontaneously associate numerosities with numerical symbols (Arabic numbers 1-8).