The computer training system is for training working memory capacity of a user of a computer within the system. A computer program is used within the system. A first task of a first difficulty level is presented to the user. A delay of a predetermined time is performed, during which delay the task is not visible or audible to the user. During the delay it is not possible to enter an answer into the computer. The difficulty level of a subsequent task to be presented to the user is changed in accordance with predetermined adaptation rules and the evaluation such that the difficulty level of the subsequent task approaches the memory capacity of the user. Subsequent tasks are presented to the user until a predetermined time limit is exceeded or until a predetermined number of tasks have been performed.