Abstract: This article presents the results of a mixed-approach research study, where the eye movement of the undergraduate students of the Austral University of Chile is examined while solving a questionnaire where tacit models appear, related to mathematical infinity, to determine possible correlations between the ocular activity parameters and the level of difficulty of each of these models. The categories of the level of difficulty were established based on two types of criteria: a subjective one, through an evaluation, carried out by the subjects, and a behavioral one, related to obtaining the correct solution. The correlations of these criteria with the ocular activity parameters were identified and considered indicators of mental effort. The analysis of the data obtained allowed us to observe discrepancies in the categorization of the tacit models based on subjective and behavioral criteria. There was a negative correlation of the eye movement parameters with students' opinionabout question difficulty levels. In contrast, a strong positive and significant correlation was noted between the presence of these models and the level of difficulty, determined by the percentage of correct answers. In turn, the percentage of correct answers had a strong positive and significant correlation with most of the ocular activity parameters. These results conclude that these parameters can be used to index this activity's tacit model's difficulty level.

Keywords: Tacit models; eye tracking; neuropsychology; cognitive process; learning; mathematics teaching