Table 1.

Task blocks for assessing the functionality of counting.

Task	Task description	Correct solution criterion
Block 1. Formal
1.1. Counting forward	Petya wanted to count to 20. He started counting: 1, 2, 3… but lost track. How should Petya continue counting? 1, 2, 3, go on!	Continues counting correctly from where Petya stopped, without returning to 1 (4, 5, 6... 20)
1.2. Counting backward	One boy was learning to count backwards. He started counting like this: 13, 12, 11, 10 … and then he got mixed up. How should he have continued counting? 13, 12, 11, 10, go on!	Correctly continues: 9, 8, 7... without going back to 13
1.3. Numeral recognition	I need to dial this phone number. Please dictate it to me! (The experimenter shows the child a printed slip of paper with numbers 2856013974)	Names all the numbers in sequence without omissions or confusion
Block 2. Reasonable
2.1. Missing number task	A boy was hanging flags in numerical order (here they are—the experimenter shows a picture with flags from 1 to 9; 2, 4, 5 are missing; 6 and 7 are swapped). Which flags still need to be hung? Where should each one go?	When naming the resulting sequence, notices and corrects the transposition (6 and 7)
2.2. Unitizing of sets as units	Masha collects beautiful buttons. Her mom gave her a box with four buttons! How many buttons does she have now? Here they all are! (the child is shown a picture with two buttons in a row, then a box with the number 4, then another button) Count all of Masha's buttons! Point with your finger as you count	Counts, taking into account the number of buttons in the box, and arrives at 7 (the experimenter first confirms understanding by asking: “how many buttons are in the box?)”
2.3. Counting objects (changing counting unit)	The child is shown a picture of 9 blocks (3 cones, 4 cylinders, 2 spheres) in a pile: ≪The children were given a box of blocks. Each of them started counting them—each in their own way. Masha counted: “Four!”—“Correct!” said the teacher. Petya counted: “Three!”—“Also correct!” said the teacher. Vasya counted: “Nine!”—“That is also correct!” said the teacher. What did each child count?≫	Correctly states what each child counted: Masha—cylinders, Petyacones, Vasya—all shapes
2.4. Counting in sets (set comparison)	Three children came to the park, and there a clown was handing out balloons! And not one at a time, but TWO balloons for each child! The clown was holding this many balloons (the experimenter shows a picture with 5 balloons), counted the children, and said: “Oh! There aren't enough balloons! I'll go get more so there will be enough!” How many more did he bring?	Correctly determines how many balloons are missing (e.g., there are 3 children → 6 are needed; 5 are available → 1 is missing)
Block 3. Functional
3.1. Comparison of discrete quantities	Two rows of five identical buttons each (gray and black) are presented. The child is asked whether there are the same number of buttons in each row. Regardless of the answer, the experimenter explains that Petya adjusted the black row (demonstrating that he spread the buttons apart), and then Nastya said, “What have you done? Now there are fewer gray buttons. You'll have to add some.” She then added two more gray buttons so that the ends of the rows again aligned. The child is then asked whether the rows now have the same number of buttons	States that after the buttons were spread apart, the quantity did not change. After the addition of two buttons, states that there are now more.
3.2. Length comparison	Two straight “paths” made of matches of equal length are presented. The child is asked whether the paths are the same length. Regardless of the answer, the experimenter explains that Petya rearranged the matches in the top row like this (making the path zigzag) and asks whether one path has become longer or whether they are still the same length. Regardless of the answer, the experimenter says, “But Olya said that one path is now shorter, so Petya added one match to it” (a match is added to the top so that the ends of the rows align). The child is then asked whether the paths are now the same length.	States that after the shape of the top path was changed, its length remained the same. After a matchstick was added, states that it became longer.
3.3. Area comparison	Two rugs made of identical small squares are presented (for example, one in the shape of a rectangle and the other in an L-shape or another figure). The child is asked whether the rugs take up the same amount of space or if one takes up more space. Regardless of the answer, the child is told that the rug in the first room was rearranged into a “path” (an elongated strip) so that it would not get in the way of the furniture. The child is then asked which rug now takes up more space.	States that the area did not change despite the change in shape