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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
Experimental setup. The subject wears the eye tracker. A number with 3 or 4 digits is shown by the projector on the white board located 1 m in front of the subject. The switch to change the question is placed on the desk.