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1 IAPS Young researchers workshop Glasgow, June GENERAL INFORMATION Name: Lien Dupont Department, University: Ghent University, Geography Department Title of Ph.D. program: The use of eye tracking in landscape perception research Sypervisor name: Veerle Van Eetvelde THESIS INFORMATION Title of the proposed paper The use of eye tracking in landscape perception State of development of thesis Preliminary analyses and results have been obtained (see below). Research problem and its novelty, cultural and environmental context in which the research is being conducted, theoretical framework and relevant literature Although landscape is a complex phenomenon, it became a popular concept and study object during recent years. When asking to describe what landscape is, many different nuanced descriptions emerge. An important, formal and internationally accepted definition is formulated by the European Landscape Convention: Landscape is an area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors (Council of Europe, 2000). According to this definition people are put in the core of the landscape and are even part of it while perceiving the landscape. Furthermore, the Convention states that landscape is an important public interest which constitutes a considerable part of the quality of life for people everywhere. Consequently, an active participation of the public in landscape planning and management is strongly stimulated, for example, by the formulation of the aspirations of the public with regard to landscape features of their surroundings by the competent authorities (Council of Europe, 2000). Considering these statements, it is important to gain insights into the way people observe and perceive landscapes to include this knowledge into landscape planning and management. So far, different landscape perception paradigms have been formulated (Scott and Benson, 2002) and analysed using questionnaires and depth interviews. The most frequently used stimuli in 1

2 these empirical researches are photographs or in situ observations (e.g. Hägerhäll, 2000; Ode et al., 2008; Palmer, 2004; Sevenant, 2010; Tveit, 2009). An objective manner to measure people s observation of landscape, however, is provided by eye tracking. This technique allows recording the speed and direction of eye movements (saccades) and the position and duration of fixations while observing images. Eye tracking measurements are well known in the field of environmental psychology (e.g. Berto et al., 2008). It has, however, also been introduced in geography (e.g. Antonson et al., 2009), cartography (e.g. Ooms et al., 2010a and 2010b) and landscape science (e.g. De Lucio et al., 1996; Tveit et al., 2010). Because landscape photographs are often used in landscape perception research (Sevenant and Antrop, 2011) eye tracking is a powerful fool for analysing people s observation of landscapes. Subsequently, these objective measurements can be compared to data collected from questionnaires, related to the aesthetic and cognitive variables of landscapes. These approaches fit into the current international research to define objective landscape indicators for landscape perception. Research aims, questions, hypotheses The central question in this research is: How do people observe landscapes? Which elements in a landscape draw attention and which do not? The research can be subdivided in three main parts: 1) Photograph based approach (finished) - Analysing the effect of different kinds of photograph stimuli (different view angles): panoramic photographs, standard photographs, detailed photographs and wide angle photographs (Figure 1). Do people observe the same landscape differently on different photograph types? If so, how do the photograph parameters influence the observation pattern of the landscapes? 2) Landscape based approach (in progress) - Analysing the effect of different landscape types: urban versus rural, cultural versus natural, open versus enclosed, homogeneous versus heterogeneous. Do the characteristics of the landscape influence the observation of the landscape? Are different types of landscapes observed differently? 2

3 - Analysing the effect of the visual composition of the landscape using different simulations of the same landscape: skyline, depth, fore- and background, presence of land marks, visual disturbances,... Can the visual composition of a landscape be measured using eye tracking? Do new developments in the landscape draw attention and are they experienced as being disturbing? 3) Respondent based approach (in progress) - Analysing the effect of groups of respondents with different backgrounds: experts versus non-experts Is there a difference in the observation of landscapes between those groups? Do they focus on the same elements in a landscape? Each eye tracking experiment is accompanied by a questionnaire in which information is gained about the landscapes shown during the experiment. This allows us to analyse if there is a difference between the data recorded during the eye tracking and what people describe they observe in the landscape. 3

4 Figure 1: Example of five photograph types: (a) panoramic photograph, (b) standard photograph, (c) zoom 1, (d) zoom 2 and (e) wide angle photograph 4

5 Research strategy, samples and methodology a) Stimuli The stimuli for the eye tracking experiment are photographs, representing different landscapes in Belgium. All photographs are taken on days with similar weather conditions and in the same season, to avoid effects of vegetation transparency. The photographs are made using a tripod to assure a constant shot height. For the experiments, all photographs are framed in the same 1280x1025 pixel dark grey background (Figure 2) to guarantee an identical display size (constant height). Figure 2: Framed photograph stimuli to allow comparison between standard photograph sizes and panoramic sizes b) Subjects For the photograph based approach, in which the effect of the photograph parameters was tested, a homogeneous group of respondents was selected to avoid a bias towards the cultural, social and educational background of the observers. As a result, a group of 23 graduated 5

6 geographers (male and female, aged between 23 and 52) of the university of Ghent and Leuven participated in the experiment as unpaid volunteers. In the respondent based approach, landscape experts and undergraduate geography students (non-experts) are tested. c) Questionnaires For each experiment a questionnaire is set up to collect information about the background of the respondents and information about the observed landscapes (which elements drew attention, which features were disturbing etc.). The questionnaires consist of open questions (e.g. Which elements draw your attention? ) and ratings (e.g. How open is this landscape on a scale of 1 to 7 ). Information on data collection and data analysis a) Apparatus The experiments are performed using an Eye Link 1000, which records the point of regard of the observer every millisecond. In particular, the system utilizes low power infrared light, which is reflected from the eye and subsequently captured by an optical sensor and analyzed by a signal processing unit. This converts the information into usable data like fixation/saccade position, fixation/saccade duration, saccade amplitude, saccade velocity etc. This procedure allows a complete reconstruction of the observer s entire scan path and an identification of the areas in the image that drew most attention, called the centres of attention (Buswell, 1935). b) Eye tracking experiment The experiments are executed in a laboratory at Ghent University, isolated from the external world so that participants cannot be distracted. Each test is preceded by a calibration procedure to match the system coordinates with the subject s real point of regard. This is achieved by multiple calibration trials in which the subject was asked to fixate nine dots appearing separately in a 3x3 grid. During the experiment, the subjects are asked to freely view the randomly displayed photographs. The participants are given no specific tasks; no particular information needs to be found. During the trials the system records numerous data like the number, position (x,y) and duration (in milliseconds) of fixations and the number, length and speed of saccades. 6

7 c) Data processing and statistical analysis The data recorded during the eye tracking experiment are saved in EDF-files by the system. For the analysis these files are converted into Excel-files, which contain complete, well organized and usable trial and fixation reports. These files are then used to statistically analyse the data. This analysis is executed in the software package SPSS. The goal of the first experiment was to test whether the photograph type has an effect on the observation pattern of landscape photographs (photograph based approach). A comparison of means between the different photograph types was thus executed for the variables measured by the eye tracking system. A Kolmogorov-Smirnov test was performed to determine if the data follow a normal distribution, which did not seem to be the case. Consequently, an Analysis of Variance (ANOVA) was not allowed. Instead, the equivalent of the ANOVA-test for nonparametric data, the Kruskal-Wallis test, was performed for testing the equality of means. Where this test indicated unequal means, information about the comparative magnitudes of the means was obtained using a Dunn s test. Based on these tests, groups of similar means were formed and differing means were identified. d) Data visualization The Data Viewer provides a tool to display all recorded data on the original photographs. Although this does not enable a strong analysis of the data, it is a very helpful tool to visualize the results from the statistical analysis. Different kinds of maps can be created. Figure 3 is a visualization of the fixations and saccades. The circles represent the fixations, while the arrows illustrate the eye movements between two fixations (saccades). In both cases the numbers indicate the duration of the fixation/saccade in milliseconds. Figure 4 is an example of a heat map, which can be derived from the fixation and saccade map. This map shows the centres of attention. The red zones on the photograph indicate the areas that have been observed most frequently and intensively. 7

8 Figure 3: Visual output of one test person: fixations (circles) and saccades (arrows) indicating the eye movements Figure 4: Heat map of entire test population Findings and their discussion (preliminary or advanced, where available) a) Photograph based approach The Kruskal-Wallis test indicates a significant difference in the number and duration of fixations and in the number, length and speed of saccades for the panoramic photograph compared to the other photograph types. In particular, the experiment reveals that people generate more fixations and saccades in panoramic photographs. In addition, the saccades length and speed also seems to be higher in this photograph type, while the fixation duration is significantly lower. This means that people tend to scan the whole photograph, independent of the photograph size and the view angles. In panoramic photographs quantitatively more information is extracted as subjects make more fixations. However, the extraction quality decreases because of the shorter fixation duration. Furthermore, the observed horizontal and vertical area is significantly different between the panoramic photographs (70 horizontal view angle, 20.9 vertical view angle) and the detailed 8

9 photographs (15.8 horizontal view angle, 10.5 vertical view angle). In panoramic photographs, the vertically observed area is smaller as people scan the photographs mainly in a horizontal direction. The opposite applies to the detailed photographs, which are rather observed in a vertical direction. b) Landscape based approach According to the statistical analysis, the landscape characteristics and landscape type have no influence on the observed horizontal area of a photograph. In contrast, the degree of openness seems to have an effect on the number of fixations and saccades, the fixation duration, the saccade speed and the observed vertical area of the photographs. In particular, open landscapes are characterized by a smaller amount of fixations and saccades, while the fixation duration and saccade speed are larger. Fixations in enclosed landscapes seem to be shorter. Furthermore, enclosed landscapes are observed in a more vertical direction, probably because of the presence of large vertical objects like trees, forests or buildings in these landscapes. The second landscape characteristic, the degree of heterogeneity also influences the observation pattern. A difference in saccade length, saccade speed and observed vertical area can be detected. More specifically, the experiment indicates that the subjects make longer and faster eye movements in homogeneous landscapes. Moreover, homogeneous landscapes are observed in a more vertical direction compared to heterogeneous landscapes. The more monotonous character of homogeneous landscapes can explain this trend. People may start searching for interesting elements in this kind of landscapes, explaining the longer and faster saccades. Finally, the influence of the landscape type on the observation of landscape photographs is more complex to interpret as the influence of the different landscape characteristics (openness and heterogeneity) is combined. Though, some conclusions can be drawn from the statistical analysis. Open-homogeneous landscapes seem to be significantly different for a number of variables. First, this landscape type is characterized by a lower number of fixations and saccades. However, by way of compensation, the mean duration of the fixations is longer. In contrast, the fixation duration in enclosed-homogeneous landscapes is shorter. Furthermore, the saccade length and speed are significantly higher in open and enclosed-homogeneous landscapes. In both cases, these results can again be explained by the monotonous character of homogeneous landscapes, which cannot hold the observer s attention and makes him/her search for more interesting features. Finally, the observed vertical area differs between semi- 9

10 open-heterogeneous and enclosed-homogeneous landscapes. While the observed vertical area on photographs of semi-open-heterogeneous landscapes is smaller, enclosed-homogeneous landscapes are perceived in a more vertical direction. Expected theoretical contribution of the research The objective eye tracking measurements will be compared to data collected from questionnaires, assessing the landscape perception and preference and their determining variables. The aim is to define objective landscape indicators for landscape perception and preference. Expected policy implications of research findings The results of this empirical research will be used to formulate suggestions and recommendations for landscape design and planning, for example, how to cope with disturbances in the landscape (like placing signs, commercial announcement, new infrastructure, greenhouses, wind turbines,...). The applications in urban and spatial planning are the designs of green spaces in urban areas, parks, playgrounds, infrastructure,... EXPECTED FEEDBACK How to set up useable questionnaires? How to (statistically) analyze the results of questionnaires? Are there any other experiences using eye tracking in landscape perception research? How can the results be used in landscape policy and landscape management? How to publish my results? 10

11 References 1. Antonson, H., Mardh, S., Wiklund, M., Blomqvist, G., Effect of Surrounding Landscape on Driving Behaviour: A Driving Simulator Study. Journal of Environmental Psychology, 29, Berto, R., Massaccesi, S., Pasini, M., Do Eye Movements Measured across High and Low Fascination Photographs Differ? Addressing Kaplan's Fascination Hypothesis. Journal of Environmental Psychology, 28, Buswell, G., How People Look at Pictures: A Study of the Psychology of Perception and Art. Chicago, University of Chicago Press. 4. Council of Europe, European Landscape Convention and Explanatory Report. Council of Europe, Document by the Secretary General established by the General Directorate of Education, Culture, Sport and Youth, and Environment, Florence. 5. De Lucio, J. V., Mohamadian, M., Ruiz, J. P., Banayas, J., Bernaldez, F. G., Visual Landscape Exploration as Revealed by Eye Movement Tracking. Landscape and Urban Planning, 34, Hägerhäll, C.M., Clustering Predictors of Landscape Preference in the Traditional Swedish Cultural Landscape: Prospect-refuge, Mystery, Age and Management. Journal of Environmental Psychology, 20, Ode, A., Tveit, M.S., Fry, G., Capturing Landscape Visual Character Using Indicators: Touching Base with Landscape Aesthetic Theory. Landscape Research, 33, Ooms, K., Antrienko, G., Andrienko, N., De Maeyer, P., Fack, V., 2010a. Visual Analytics on Eye Movement Data reveal Search Patterns on Dynamic and Interactive Maps. Proceedings of the 5 th National Cartographic Conference (GeoCart 2010): Cartographies for Tomorrow: mapping in a Mashed-up World. New Zealand Cartographic Society, Auckland. 9. Ooms, K., De Maeyer, P., Fack, V., 2010b. Analyzing Eye Movement Patterns to improve Map Design. Proceedings of the 18 th International Research Symposium on Computerbased Cartography and GIScience (AutoCarto 2010): Geospatial Data and Geovisualisation 11

12 for the Environments, Security and Society. Cartography and Geographic Information Society, Orlando. 10. Palmer, J.F., Using Spatial Metrics to Predict Scenic Perception in a Changing Landscape: Dennis, Massachusetts. Landscape and Urban Planning 69, Scott, K., Benson, F., Public and Professional Attitudes to Landscape: Scoping Study. Landscape Research Group, School of Architecture, Planning and Landscape. Newcastle, University of Newcastle. 12. Sevenant, M., Variation in Landscape Perception and Preference. Experiences from Case Studies in Rural and Urban Landscapes Observed by Different Groups of Respondents. Doctoral dissertation, Ghent University, Department of Geography, Ghent. 13. Sevenant, M. and Antrop, M., Landscape Representation Validity: A Comparison between On-site Observations and Photographs with Different Angles of View. Landscape Research, 36 (3), Tveit, M.S., Indicators of Visual Scale as Predictors of Landscape Preference; a Comparison between Groups. Journal of Environmental Management, 90, Tveit, M.S., Hägerhäll, C.M., Nordh, H., Ode, A., Identifying Cues of Stewardship in Everyday Landscapes using Eye Tracking. Proceedings of the 21 st IAPS Conference: Vulnerability, Risk and Complexity: Impacts of Global Change on Human Habitats. IAPS, Leipzig. 12