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Dott. Marco Pedrotti

  • Dottorato: 23° ciclo
  • Matricola: 336542

Tesi di dottorato

                                                COGNITIVE ACTIVITY AND EYE MOVEMENTS:

                             PUPIL DILATION AS AN INDEX OF INSTANTANEOUS MENTAL WORKLOAD

                                                                       Introduction.

The aim of my Ph.D. course is investigating human mental workload using eye movements as indicators: two main issues appear thereof.


First, the concept of mental workload is itself controversial, and no shared definition exists within the scientific literature (Xie & Salvendy, 2000). Thus, adoption of a single definition is essential for narrowing the field of intervention of the research. Once this is done, I believe the research topic should be at least related to a concrete problem, and error prediction was chosen. The scope of this thesis is establishing a relationship between observable behavior (i.e. errors) and the physiological variable pupil dilation - which is known to vary with mental workload. When a person experiences mental workload (increased vigilance or an increased load on working memory), the resultant brain activity causes a dilation of the pupils (Klingner, 2010). However, inferring psychological significance from physiological signals is to date a complex task (Cacioppo & Tassinary, 1990): despite advances in physiological signal acquisition, serious lacks still exist in signal representation and, most of all, interpretation of results. For testing the possible existence of a relationship between the occurrence of errors - in a mentally engaging task - and pupil diameter variations, a laboratory experiment was carried out.


Second, mental workload assessment is a complicate issue as well. Historically, three main classes of measures have been used: subjective, behavioral, and physiological. Within the latter, eye movements have been found to provide important information on cognitive processing (Rayner, 1998). Pupil dilation presumably reflects the amount of effort an individual experiences while performing mentally engaging tasks (Beatty & Lucero-Wagoner, 2000). Hence, the idea of relating particular signal patterns to observed behavior.


The first part of the thesis will be dedicated to the definition of the term "workload". It will be shown that many definitions exist, and three main contributions will be outlined: an internationally standardized definition, an attention and resource theory approach, and a prediction-oriented conceptual framework. Following, the experimental setup will be outlined. A methodological work on pupil signal treatment will be described, which comprises the development and implementation of an ad hoc algorithm eyeblink detection and missing data recovery. Finally, the results will be presented and discussed.

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