Visual Analysis of Dyslexia on Search Andrew Macfarlane1, Areej Al-Wabil2, Gennady Andrienko3, Natalia Andrienko3 and George Buchanan1 1. Centre for HCI Design, City, University of London, Northampton Square, London EC1V 0HB 2. Ideation Lab, School of Engineering, MIT, Cambridge, MA. USA 3. giCentre, City, University of London, Northampton Square, London EC1V 0HB ABSTRACT A key problem in the field of search interfaces is dyslexic users interaction with the UI. Dyslexia is a widespread specific learning difficult (SpLD) (10% of any population is estimated to have this cognitive disability) which is under researched in the field of information retrieval. The focus here is an analysis of the User Interface (UI) for search, using visual analytical methods on eye tracking data to examine the difference between control and dyslexic searchers. We use a n umber of visual analytic methods including path similarity analysis (PSA) and clustering of time Intervals to demonstrate both similarities and differences between the user groups. Observations of videos are used to augment the visualizations. Results demonstrate a clear difference between the user groups, and a clear memory effect on the user of search interfaces is shown – this is a key contribution of this paper. We examine the results using of theories of dyslexia, contributing also to the field of dyslexia and search. Fig 1 - Experimental procedure Fig 2 – Experimental Setup Fig 3 – OKAPI User Interface Fig 4 - Raw scanpath data Fig 5 - Raw Heatmap Data Fig 8 – Distributions of points with trajectory segments between two main clusters removed Shows a clearer pattern of interactions within the clusters, showing horizontal and vertical moves. The upper cluster is the results list, which tends to be horizontal, the lower cluster is document views with both horizontal and vertical moves. This interaction occurs after the first iteration, the initial query was set for the experiment and no further interaction was possible with the query pane, hence the concentration of user eye movements in the results list/document view pane (see figure 3). Fig 10 – Dyslexic group frequency distribution of moves For the dyslexic user group, we see high frequencies of both horizontal and vertical movements. The frequencies of vertical movements are almost as high as for the horizontal movements and much higher than for the diagonal movements. Difference between the user groups is that control users look more left to right, whereas dyslexic users often look down (0°=360°) and up (180°), e.g. to a previous point in a displayed document Fig 6 – Distribution of points from eye tracks Two large and dense clusters of the fixations can be observed. The main clusters differ in spatial extents but have very similar internal structures. Each cluster consists of sub-clusters separated by vertical and horizontal gaps. Fig 7 – Voronoi tessellation of moves between clusters Summarizes the movements from the trajectories into moves (or flows) between the cells. It is clear that the main flows are between the right parts of the two main clusters. There are also smaller flows between the left parts of the main clusters. However, there were very few or no movements between the left and right parts within the clusters and between the left part of one cluster and the right part of the other cluster. Fig 9 – Control group frequency distribution of moves Clear prevalence for horizontal movements (90° and 270°) frequencies of the vertical movements (around 0°=360° and around 180°) are not much higher than for diagonal movements.