An apparatus for determining a cognitive state of a user of a mobile device (2) of the apparatus (1), the apparatus (1) comprising: an output means (5) in the mobile device (2) for giving out information to the user, wherein the output means (5) comprises an optical output means (5.1) for optically giving out information to the user； a camera (3) in the mobile device (2) 5for recording images in a first view direction (3.1) of an environment of the mobile device (2)；a path means (6) configured to determine a positional path of the mobile device (2) in the environment； a further camera (4) in the mobile device (10) for recording images in a second view direction (4.1) and/or a microphone (13) for recording an audio signal； a task means (7, 7') 10for interacting via the output means (5) with the user to make the user solve a task using an augmented reality environment shown via the optical output means (5.1) and based on the environment of the mobile device (2) captured by the camera (3)； a user feature means (8, 8') for detecting and/or tracking at least one feature of the user in the images recorded by 15the further camera (4) while the user solves the task and/or in the audio signal recorded by the microphone (13) while the user solves the task； a cognitive state means (9, 9') for determining the cognitive state of the user based on the positional path of the mobile device determined while the user solves the task and based on the at least one feature of the user.L'invention concerne un appareil permettant de déterminer un état cognitif d'un utilisateur d'un dispositif mobile (2) de l'appareil (1), l'appareil (1) comprenant : un moyen de sortie (5) dans le dispositif mobile (2) pour transmettre des informations à l'utilisateur, le moyen de sortie (5) comprenant un moyen de sortie optique (5.1) pour transmettre optiquement des informations à l'utilisateur； une caméra (3) dans le dispositif mobile (2) 5 pour enregistrer des images dans une première direction de visua
