Touch-typing
While accommodated in the controlled environment, all subjects underwent a five-day long course on typing on a keyboard with all ten fingers (touch-typing, 10-finger-system-typing) on the keyboard layout QWERTZ. In the 10-finger-system of touch-typing each character on the keyboard has a defined finger assigned to it (e.g., F: index finger left), whereas self-taught typing-styles vary heavily. All subjects completed their course with the free Tipp10® software (Thielicke IT Solutions, Version 2.1) on the same type of notebook with the same type of keyboard (Lenovo® Thinkpad T60). The lessons were identical in content and therefore in skill demands for both groups. Two 45-min sessions of training were applied each day. The difficulty of typing regarding motor skill requirements was increasing over the five days of the trial through expanding letter variance and word complexity. The course was always supervised by trained personal to guarantee a correct procedure, including the use of all ten fingers and correct finger-character combinations. No feedback was given to subjects concerning their typing performance. Consequential errors were avoided by the used software as only the correct letter input would enable progress. Quiet surroundings to avoid distraction or disturbance were established by members of the study team.Each day, the first session took place from 9 to 9.45 or 9.45 to 10.30 AM with the two groups alternating between the dates. The second session took place from 3 to 3.45 or 3.45 to 4.30 PM with the two groups alternating between the dates as well. The two groups trained in direct succession and separately. Every training session consisted of a repeated sequence of a total of 18 different lessons following a set schedule. Three different and consecutive lessons of 3 min each were followed by a break of 2 min. This sequence was repeated three times before the final sequence concluded the session without a following break. Thus, each session consisted of 12 lessons and 3 breaks, resulting in an overall 42-min duration. A 3-min buffer was included for possibly necessary explanations from the supervising personnel, summing up to 45 min total duration for one session. The difficulty was steadily increased over the subsequent lessons by introducing new characters (except the last lesson, which included all characters), areas on the keyboard and by increasing the distance between characters. The frequency of each lesson throughout the course was determined in advance by its contents’ usefulness to promote motivation and progress. The content, procedure, and duration of first (morning) and second (afternoon) daily session was identical. Thus, the participants were trained through 24 3-min-long lessons per day separated into 2 daily sessions.Lesson 3 (L3) was selected beforehand as a marker for the training effect and was carried out repeatedly and in each training session over the trial. On the first day, this marker lesson was completed 4 times in the morning training session and 4 times in the afternoon training session, as it was part of the normal training in addition to being a training effect marker. On each of the following four days, the marker lesson was completed twice per day—once in the morning training session and once in the afternoon training session. This specific lesson was chosen, because it occurred early in the course and both pilot trial subjects and study team judged it to be neither hard nor easy. The subjects were unaware of the specific function of this lesson.The baseline typing skill (i.e., general agility of hand and fingers) were (a) the number of correctly typed characters in 1 min (correct characters per minute, 