LEE- Geomatik Mühendisliği-Doktora
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ÖgeExploring the cognitive processes of map users employing eye tracking and EEG(Fen Bilimleri Enstitüsü, 2020) Keskin, Merve ; Doğru, Ahmet Özgür ; De Maeyer, Philippe ; 656904 ; Geomatik Mühendisliği Ana Bilim DalıUnderstanding how our brain copes with complex visual information is a challenge for both cognitive psychology and cartography. If we pursue to design better and usable maps, we require building a better knowledge on the cognitive processes of map users. This thesis aims to contribute to the understanding of the cognitive processes of a group of map users in learning, acquiring and remembering information presented via digital 2D static maps. To be able to gain insight into the users' behaviors while they interact with maps, eye tracking (ET) and electroencephalogram (EEG) are enabled as synchronized data collection methods due to them being non-invasive and capturing direct responses of cognitive activities. Therefore, the preliminary goal of the research is to evaluate the use of ET and EEG for cartographic usability and spatial cognition research considering the technical and methodological aspects of this synchronization, also the limitations, possibilities and the contribution of EEG in the domain of cartography. The technical concerns refer to (i) the synchronization of ET and EEG recording systems, their accuracy and quality, and (ii) numerous processing steps (i.e. preprocessing, the alignment of the collected ET and EEG data, removal of non-cerebral activities from EEG data, segmentation and re-referencing). The methodological issues are situated in many aspects of the experimental design and its set-up, which includes identifying the research goals, participants, task and stimuli, psychological measures to use, evaluation methods and possible analyses of the collected data. These issues are pinpointed with respect to the existing literature, knowledge obtained from domain experts and hands-on experience in the neuro-lab. The fundamental object of the thesis is to investigate on the traditional expert-novice paradigm as expertise being one of the individual characteristics that influences the users' performance on map-learning tasks. Since maps are widely used by both experts and novices, to study their differences in spatial cognition enables us to determine how to use this input to enhance the map design leveraging the map users' cognitive abilities. Therefore, our main research questions are: 'Do map learning strategies of experts and novices differ? How does the cognitive load vary between expert and novices?' In this context, we conducted two mixed-methods user experiments focusing on the cognitive strategies of a group of expert and novice map users and investigated their spatial memory capabilities through cognitive load measurements. First experiment had a simple design and an exploratory characteristic, since we would initially assure that the eye tracking and EEG synchronization is of sufficient quality to explore users' cognitive behaviors towards map stimuli. Accordingly, it consisted of single trials and participants were instructed to study the main structuring elements of a map stimulus (i.e. roads, settlements, hydrography, and green areas) without any time constraints in order to draw a sketch map afterwards. On the one hand, the performance of the participants was assessed based on the order with which the objects were drawn on the digital sketch maps and the influence of a subset of visual variables (i.e. presence & location, size, shape, color). On the other hand, trial durations and eye tracking statistics such as the average duration of fixations, and number of fixations per seconds were compared. Moreover, selected AoIs, which represent the main structuring elements of the map stimulus, were explored to gain a deeper insight on visual behavior of map users. Based on the evaluation of the drawing order, we observed that experts and males drew roads first whereas; novices and females focused more on hydrographic object. According to the assessment of drawn elements, no significant differences emerged between neither experts and novices, nor females and males for the retrieval of spatial information presented on 2D maps with a simple design and content. The differences in trial durations between novices and experts were not statistically significant while both studying and drawing. Similarly, no significant difference occurred between female and male participants for either studying or drawing. Eye tracking metrics also supported these findings. For average duration of fixation, there was found no significant difference between experts and novices, as well as between females and males. Similarly, no significant differences were found for the mean number of fixation. Furthermore, based on results of time to first fixation, dwell time, fixation count, the number of fixations per second, average fixation duration for selected AoIs, the larger AoIs were gazed at earliest and the dwell times for such objects were much longer compared to those for other AoIs. The linear features were easier to learn and remember, although the viewer did not pay much attention. Longer average fixation durations for a specific AoI indicated that the chances were higher to remember that object. The objects that were absent on the sketch map received the shortest fixation durations during the study phase. However, longer fixation durations may also indicate participants' difficulty to recognize the information in the map stimulus. Regarding to the EEG Frontal Alpha Asymmetry calculations, both user groups showed greater relative right frontal activation, which is in association with the less attentional, and focus performance. The difference between experts and novices was not significant, similar to the eye tracking results. On the contrary, alpha power averaged across all electrodes demonstrated that the novices exhibited significantly lower alpha power, indicating a higher cognitive load. On the contrary, in Experiment 2, a complex and more structured approach was followed as a result of learning from the previous experiment and collaborating with the domain experts. This experiment contained a larger number of stimuli were used to study the effect of task difficulty (i.e. easy, moderate, hard) on the retrieval of map-related information. Next to the reaction time and success rate, we used fixation and saccade related eye tracking metrics (i.e., average fixation duration, the number of fixations per second, saccade amplitude and saccade velocity), and the event-related changes in EEG power spectral density (PSD) for alpha and theta frequency bands to identify the cognitive load. While fixation metrics and the qualitative analysis of the randomly selected focus/heat maps summarizing the participants' fixation behaviors indicated no statistically significant difference between experts and novices, saccade metrics proved the otherwise. EEG power spectrum analysis, on the other side, suggested an increase in theta power (i.e. event-related synchronization) and a decrease in alpha power (except moderate tasks) (i.e. event-related desynchronization) at all difficulty levels of the task for both experts and novices, which is an indicator of cognitive load. Although no significant difference emerged between two groups, we found a significant difference in their overall performances when the participants were classified as good and relatively bad learners. Triangulating EEG results with the recorded eye tracking data and the qualitative analysis of randomly selected focus maps indeed provided a detailed insight on the differences of the individuals' cognitive processes during this spatial memory task. The qualitative analysis with the 10 randomly selected focus/heat maps provided a general overview of the participants' attentional behavior towards the map elements of interest and the similarities related to their map learning strategies. However, for measurable results, we selected one map stimulus and drew AoIs around key elements of maps (i.e. green areas, water bodies, major rivers and roads, road junctions) to analyze the attention distribution of the participants using average fixation duration, time to first fixation and the number of map objects covered within AoIs. Although the results are preliminary, we found out that the eye scans through linear objects and fixates/focuses on the polygon objects. The location of the map elements is more influential on the participants' gaze behavior compared to its size. The fixation durations within the (relevant) AoIs did not depend on the task difficulty. Additionally, our analysis showed that the GL experienced the least cognitive and this finding supports the evaluation of the participants by classifying them as "good learners and bad learners" during the usability tests of maps designed for general users with basic map learning tasks. In order to increase the understandability and usability of cartographic products, the results of this research can be used as guiding experiences in production processes where design methods that minimize the factors that negatively affect user perception (e.g. exaggeration, reduction of emphasis, utilizing the visualization elements to increase visual extraction such as grids).