Pre‐ and post‐measurements
The pre‐ and post‐measurements included three computer‐based neuropsychological tests, carried out in one session from 8.30 to 11.00 a.m. in a quiet room, and in counterbalanced order in each group. Each participant performed the tests in comfortable sitting position on a chair at a table, with his/her elbows/arms resting on the table. The height of the chair was adjusted for each child so that the knee angle was approx. 90°. The participants viewed the screen from a distance of approx. 52 cm. The tests were performed with the use of a laptop computer with a screen of 15 in. and the resolution of 1920 × 1080 pixels.At the beginning of each test, the tester provided the participant with very brief instructions on the test task and procedure. The participant then obtained the computer‐driven instructions and performed practice trials of the test (see below). When it was obvious that he/she understood the task, the test followed.