Cogn Process (2012) 13 (Suppl 1):S261–S265 DOI 10.1007/s10339-012-0499-z
SHORT REPORT
Gaze and eye-tracking solutions for psychological research Maria Laura Mele • Stefano Federici
Published online: 19 July 2012 Ó Marta Olivetti Belardinelli and Springer-Verlag 2012
Abstract Eye-tracking technology is a growing field used to detect eye movements and analyze human processing of visual information for interactive and diagnostic applications. Different domains in scientific research such as neuroscience, experimental psychology, computer science and human factors can benefit from eye-tracking methods and techniques to unobtrusively investigate the quantitative evidence underlying visual processes. In order to meet the experimental requirements concerning the variety of application fields, different gaze- and eye-tracking solutions using high-speed cameras are being developed (e.g., eye-tracking glasses, head-mounted or desk-mounted systems), which are also compatible with other analysis devices such as magnetic resonance imaging. This work presents an overview of the main application fields of eyetracking methodology in psychological research. In particular, two innovative solutions will be shown: (1) the SMI RED-M eye-tracker, a high performance portable remote eye-tracker suitable for different settings, that requires maximum mobility and flexibility; (2) a wearable mobile gaze-tracking device—the SMI eye-tracking glasses— which is suitable for real-world and virtual environment research. For each kind of technology, the functions and different possibilities of application in experimental
M. L. Mele (&) Department of Psychology, Sapienza University of Rome, Rome, Italy e-mail:
[email protected] S. Federici Department of Human Science and Education, University of Perugia, Perugia, Italy
psychology will be described by focusing on some examples of experimental tasks (i.e., visual search, reading, natural tasks, scene viewing and other information processing) and theoretical approaches (e.g., embodied cognition). Keywords Portable eye-tracking technology Remote eye-tracking technology Psychological research
Introduction Eye-tracking technology is a set of methods and techniques used to detect and record the activities of eye movements. The research on eye movements has spread over the years along with advances in eye-tracking technology and psychological theory on the relationship between eye behavior and cognitive processes. Since eye movements provide an insight into problem solving, reasoning, mental imagery and search strategies (Jacob and Karn 2003), research in psychology has largely used objective methods to investigate how eye movements are related to cognitive processes during visual tasks. Over the past 30 years, remarkable improvements in the development of eye-tracking systems have permitted practitioners to obtain more accurate eyegaze measurements with less intrusive technologies. A wide variety of eye-tracking techniques are available, and they can be divided from a system analysis viewpoint into diagnostic or interactive techniques. ‘‘In its diagnostic role, the eye-tracker provides objective and quantitative evidence of the user’s visual and (overt) attentional processes’’(Duchowski 2002, p. 455), whereas, in its interactive role, the eye-tracker is used as interactive system responding to or interacting with the user on the basis of observed eye movements. Different eye-tracking systems
123
S262
have been developed to record eye movements during visual interaction or as input devices for communication and control. This work focuses on the diagnostic role of eye-tracking systems in different fields of experimental psychology by highlighting how objective measures underlying a user’s cognitive processes can be obtained with different eye-tracking technologies through unobtrusive methods.
New eye-tracking solutions: the SMI RED-M and the SMI eye-tracking glasses Traditionally, research on eye movements has used eyetracking technologies by means of invasive techniques that required supplemental components such as contact lenses, chin rests or bite bars (Fig. 1). Due to the physical constraints imposed on subjects, these technologies were often uncomfortable and suitable only for certain experimental contexts. To overcome these limitations, video-based techniques have been proposed to detect the eye position and gaze direction by means of equipment that is increasingly less intrusive and more accurate (Holmqvist et al. 2011). Recently, different gaze and eye-tracking solutions that use head-mounted, desk-mounted or eyeglass-mounted high-speed cameras—which are compatible with other analysis devices such as magnetic resonance imaging (MRI)—have been developed to meet the wide variety of application domains. This paper will examine the possibilities offered by two innovative solutions in particular: (1) the SMI RED-M eye-tracker; and (2) the SMI eyetracking glasses; two new camera-based technologies have recently released by SensoMotoric Instruments (http:// www.smivision.com).
Fig. 1 A rudimental apparatus for tracking eye movements by means of the direct contact of a lens with the cornea (Mele and Federici 2012)
123
Cogn Process (2012) 13 (Suppl 1):S261–S265
SMI RED-M eye-tracker The SMI RED-M is an eye-tracking technology developed by SensoMotoric Instruments (SMI) to set up experimental settings requiring the minimum intrusiveness in the recording instrumentation. The SMI RED-M is a USBpowered portable and ultra-light remote contact-free system that can be used on a desktop PC monitor, a personal laptop or a tablet. The technology, along with the SMI Experiment SuiteTM 360° design and analysis software, constitutes a comprehensive portable eye-tracking solution. By means of automatic eye-tracking and head movement compensation solutions, the system provides reliable binocular gaze and pupil data in a highly mobile and flexible way, regardless of the peculiarities of subjects involved in the experimentation (e.g., eye color, age, glasses, contact lenses) or environmental conditions (e.g., light of the room, position of the screen). Different measurement functions to control and analyze the subjects’ performances are available: gaze position on surfaces; pupil size; and 3D head and eye position. The system provides data extensions that can be easily processed by the SMI BeGazeTM analysis and visualization software (Fig. 2) and other statistics software (e.g., MATLABÒ, SPSSÒ, ExcelTM). Moreover, eye-tracking data can be integrated with individual setups such as the E-PrimeÒ, Python or MATLABÒ software, and custom applications written in different programming languages (e.g., C/C ?? or -NET), supporting co-registrations with other kinds of data (e.g., MRI). SMI eye-tracking glasses In 2012, SMI SensoMotoric Instruments proposed a new fully mobile gaze-tracking device, the SMI Eye-tracking Glasses, which are a non-invasive and robust system designed to be used like a common pair of glasses (weight 75 g) in different environmental studies, e.g., driving research, visual perception research or indoor/outdoor research. The system is equipped with an HD scene camera (resolution 1,280 9 960 p) and eye glasses that can be interchanged according to the experimental environment light (indoor/outdoor use). Thanks to an automatic parallax compensation mechanism that obviates the need for manual adjustments, the SMI Eye-tracking Glasses provide reliable binocular eye-tracking data in both real-time and recorded data observations, and it is easily integrable with other mobile technologies and sensors such as EEG or GPS. The system also includes a mobile recording unit and an optional software package—the BeGazeTM software— developed to aggregate data by a semi-automated dynamic Area of Interest (AOI) analysis with no need to use active markers (Fig. 3).
Cogn Process (2012) 13 (Suppl 1):S261–S265
S263
Fig. 2 Heat map created with SMI BeGazeTM eye-tracking analysis software (http://www. smivision.com/egts)
Fig. 3 Key eye-tracking data on selected areas of interest (AOIs) of a print ad created with SMI BeGaze eye-tracking analysis software (http://www.flickr.com/photos/ smieyetracking/)
123
S264
Application of eye-tracking technology in psychological research Eye movements are the result of the interaction between cognitive and perceptual processes (Richardson and Johnson 2008), and they can be a powerful way to investigate psychological processes such as language processing, image processing, auditory processing, memory, social cognition and decision-making in an unobtrusive and accurate way. As follows, different application possibilities of eye-tracking technologies in experimental psychology will be described by focusing on examples of experimental tasks: (1) visual search, (2) reading, (3) natural tasks, (4) scene viewing and (5) other information processing. Visual search The analysis of eye behavior in visual search tasks reveals objective information on how humans perceive a visual scene in situations that require visual target detection. Eyetracking visual search tasks can be divided according to the nature of the stimuli used, such as alphanumeric, textual or text-like stimuli, pictorial stimuli, complex arrays or objects (Duchowski 2002). In the investigation of human behavior related to visual search tasks, subjects are traditionally asked to search for a given target and discriminate it among several non-targets that differ from the target. Response times, eye-gaze parameters and accuracy of responses are relevant measures to be taken into account in visual search studies. Given the nature of the tasks, remote eye-tracking technologies combined with design software are the best solution for gaze-tracking experiments and visual stimuli presentation. In fact, this kind of technology (e.g., the SMI RED500 or RED-M products) provides researchers a flexible and robust system to manage their experiments and, at the same time, permit them to arrange a comfortable setting by minimizing the impact of recording instrumentation on subjects’ performance. Reading Since the second half of the 1970 s, psychology has adopted eye-tracking methodologies to investigate (overt) visual attention in reading experimental tasks. The first studies on eye movements in text reading led researchers to identify the most peculiar eye movement characteristics in reading, such as the average duration of eye fixations and saccades and the variables that influence eye movement performance such as textual, typographical or contextual features (Rayner 1998). The current remote eye-tracking systems allow practitioners to accurately operate and register eye movements during reading experiments for descriptive analyses or even to modulate the stimulus
123
Cogn Process (2012) 13 (Suppl 1):S261–S265
display in real-time according to the subject’s gaze position in different displays such as tablets, desktop screens, papers or other supports. For this field of studies, remote eyetracking technologies providing high data quality and highspeed performance are required to accurately measure saccades and shortest latencies remote contact-free setups (e.g., SMI RED 500 or iView XTM Hi-Speed products). Natural tasks The examples of application previously reported are often set up to be conducted in artificial laboratory settings; therefore, different studies investigated complex stimuli such as natural scenery. Numerous are the dynamic situations that have been observed in the eye-tracking literature (e.g., driving, sport, imagery tasks, virtual reality and usability studies), which often involves different kinds of perceptual feedback such as haptic or acoustic information. Thanks to recent advancements in portable eye-tracking technologies (e.g., the head-mounted iView XTM HED or the SMI eye-tracking glasses), today it is easy to collect eye movements in more natural situations—usually requiring unconstrained eyes, head and hand movements (Duchowski 2002)—with full freedom of movement in indoor and outdoor settings. Scene viewing Since the visual information processing mechanisms of human vision have emerged as a relevant issue in the study of perception and cognition, the investigation of eye movements by means of eye-tracking technologies has revealed a powerful way to understand scene viewing. Due to the non-intrusiveness and high portability of modern eye-tracking technologies, the measurement of eye movement patterns, related to visual and cognitive information processing, can be conducted in a wide variety of experimental contexts and situations. By means of wearable eyetracking technologies, researchers can obtain reliable and unobtrusive on-line measures of eye movements and parameters to study eye behaviors during complex visualcognitive tasks, analyze the way in which subjects acquire environmental information, and investigate how information in visual environments is dynamically processed (Henderson and Hollingworth 1998). Information processing in other cognitive tasks Eye movement studies on information processing involve a large number of other domains that can be divided according to the nature of the task (Rayner 1998). Studies on numerical and arithmetical reading and analysis, problem solving, multisensory tasks such as auditory language
Cogn Process (2012) 13 (Suppl 1):S261–S265
processing, face perception and visual training can benefit from high performance eye-tracking systems, which are suitable for a wide range of research areas and are compatible with other analysis devices such as functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), electroencephalography (EEG), or pupillometry (e.g., the iView XTM MRI-LR system).
The application of eye-tracking technology in the study of embodied cognition Since cognitive processes are deeply rooted in the body’s interactions with the world (Wilson 2002), eye-tracking methodology might be a privileged way to study embodied cognition. Cognitive sciences agree that cognition is the result of both cognitive processes and situated environmental contexts (Barsalou 1999; Clark and Chalmers 1998). Some authors recently pointed out that eye movements interacting with environmental spatial stimuli influence spatial reasoning (Grant and Spivey 2003) and, in a reciprocal way, act as an embodied mechanism guiding cognitive processing (Thomas and Lleras 2007). In the past, many studies have used different kinds of eye-tracking solutions to investigate how eye behavior affects thought and enhances reasoning(Shimojima and Katagiri 2012), and how beliefs and attitudes affect eye movements, predicting implicit associations (Mele and Federici 2013). These studies highlight how eye-tracking technologies can be particularly suitable for experimental paradigms, which assume theories of grounded cognition (Barsalou 2008, 2010).
Conclusion Different domains in scientific research such as neuroscience, experimental psychology or human factor science can benefit from eye-tracking methodology to investigate visual processes. An overview of the different possibilities for applying eye-tracking in psychology has been shown, with a special attention to two recent SMI solutions. In this paper, we have presented examples of eye-tracking application in psychology by showing different experimental tasks. Moreover, since the study of visual behavior is a privileged way to understand the relationship between body and cognition, we focused on the application of eyetracking technology in the theories of grounded cognition.
S265 Conflict of interest This supplement was not sponsored by outside commercial interests. It was funded entirely by ECONA, Via dei Marsi, 78, 00185 Roma, Italy.
References Barsalou LW (1999) Perceptual symbol systems. Behav Brain Sci 22 (4):577–609; discussion 610–660. doi:10.1017/S0140525X99 532149 Barsalou LW (2008) Grounded cognition. Annu Rev Psychol 59(1): 617–645. doi:10.1146/annurev.psych.59.103006.093639 Barsalou LW (2010) Grounded cognition: past, present, and future. Top Cogn Sci 2(4):716–724. doi:10.1111/j.1756-8765.2010. 01115.x Clark A, Chalmers D (1998) The extended mind. Analysis 58(1):7– 19. doi:10.1093/analys/58.1.7 Duchowski AT (2002) A breadth-first survey of eye-tracking applications. Behav Res Methods Instrum Comput 34(4):455– 470. doi:10.3758/BF03195475 Grant ER, Spivey MJ (2003) Eye movements and problem solving. Psychol Sci 14(5):462–466. doi:10.1111/1467-9280.02454 Henderson JM, Hollingworth A (1998) Eye movements during scene viewing: an overview. In: Underwood G (ed) Eye guidance in reading and scene perception. Elsevier, Oxford, UK, pp 269–293 Holmqvist K, Nystro¨m M, Andersson R, Dewhurst R, Jarodzka H, van de Weijer J (2011) Eye tracking: a comprehensive guide to methods and measures. Oxford University Press, New York, NY Jacob RJK, Karn KS (2003) Eye tracking in human-computer interaction and usability research: Ready to deliver the promises. In: Hyo¨na¨ J, Radach R, Deubel H (eds) The mind’s eye: cognitive and applied aspects of eye movement research. Elsevier Science, Oxford, UK, pp 573–603 Mele ML, Federici S (2012) A psychotechnological review on eyetracking systems: towards user experience. Disabil Rehabil Assist Technol 7(4):261–281. doi:10.3109/17483107.2011.635326 Mele ML, Federici S (2013) Believing is seeing: ocular-sensorymotor embodiment of implicit associations. The 1st world conference on personality, Stellenbosch, ZA, March 19–23, 2013 Rayner K (1998) Eye movements in reading and information processing: 20 years of research. Psychol Bull 124(3):372–422. doi:10.1037/0033-2909.124.3.372 Richardson DC, Johnson SP (2008) Eye tracking research in infants and adults. In: Sloutsky V, Love B, McRae K (eds) 30th Annual meeting of the cognitive science society: CogSci 2008. Washington, DC, July 23–26 2008 Shimojima A, Katagiri Y (2012) An eye-tracking study of integrative spatial cognition over diagrammatic representations spatial cognition. In: Ho¨lscher C, Shipley T, Belardinelli MO, Bateman J, Newcombe N (eds) Spatial cognition vii: international conference, spatial cognition 2010, vol 6222., SpringerBerlin, DE, pp 262–278 Thomas L, Lleras A (2007) Moving eyes and moving thought: on the spatial compatibility between eye movements and cognition. Psychon Bull Rev 14(4):663–668. doi:10.3758/bf03196818 Wilson M (2002) Six views of embodied cognition. Psychon Bull Rev 9(4):625–636. doi:10.3758/BF03196322
123
