Roy S. Hessels

Bio: Roy S. Hessels is an academic researcher from Utrecht University. The author has contributed to research in topics: Eye tracking & Gaze. The author has an hindex of 17, co-authored 52 publications receiving 885 citations.

The area-of-interest problem in eyetracking research: A noise-robust solution for face and sparse stimuli

Abstract: A problem in eyetracking research is choosing areas of interest (AOIs): Researchers in the same field often use widely varying AOIs for similar stimuli, making cross-study comparisons difficult or even impossible. Subjective choices while choosing AOIs cause differences in AOI shape, size, and location. On the other hand, not many guidelines for constructing AOIs, or comparisons between AOI-production methods, are available. In the present study, we addressed this gap by comparing AOI-production methods in face stimuli, using data collected with infants and adults (with autism spectrum disorder [ASD] and matched controls). Specifically, we report that the attention-attracting and attention-maintaining capacities of AOIs differ between AOI-production methods, and that this matters for statistical comparisons in one of three groups investigated (the ASD group). In addition, we investigated the relation between AOI size and an AOI’s attention-attracting and attention-maintaining capacities, as well as the consequences for statistical analyses, and report that adopting large AOIs solves the problem of statistical differences between the AOI methods. Finally, we tested AOI-production methods for their robustness to noise, and report that large AOIs—using the Voronoi tessellation method or the limited-radius Voronoi tessellation method with large radii—are most robust to noise. We conclude that large AOIs are a noise-robust solution in face stimuli and, when implemented using the Voronoi method, are the most objective of the researcher-defined AOIs. Adopting Voronoi AOIs in face-scanning research should allow better between-group and cross-study comparisons.

What to expect from your remote eye-tracker when participants are unrestrained.

Abstract: The marketing materials of remote eye-trackers suggest that data quality is invariant to the position and orientation of the participant as long as the eyes of the participant are within the eye-tracker's headbox, the area where tracking is possible. As such, remote eye-trackers are marketed as allowing the reliable recording of gaze from participant groups that cannot be restrained, such as infants, schoolchildren and patients with muscular or brain disorders. Practical experience and previous research, however, tells us that eye-tracking data quality, e.g. the accuracy of the recorded gaze position and the amount of data loss, deteriorates (compared to well-trained participants in chinrests) when the participant is unrestrained and assumes a non-optimal pose in front of the eye-tracker. How then can researchers working with unrestrained participants choose an eye-tracker? Here we investigated the performance of five popular remote eye-trackers from EyeTribe, SMI, SR Research, and Tobii in a series of tasks where participants took on non-optimal poses. We report that the tested systems varied in the amount of data loss and systematic offsets observed during our tasks. The EyeLink and EyeTribe in particular had large problems. Furthermore, the Tobii eye-trackers reported data for two eyes when only one eye was visible to the eye-tracker. This study provides practical insight into how popular remote eye-trackers perform when recording from unrestrained participants. It furthermore provides a testing method for evaluating whether a tracker is suitable for studying a certain target population, and that manufacturers can use during the development of new eye-trackers.

Is the eye-movement field confused about fixations and saccades? A survey among 124 researchers.

Abstract: Eye movements have been extensively studied in a wide range of research fields While new methods such as mobile eye tracking and eye tracking in virtual/augmented realities are emerging quickly, the eye-movement terminology has scarcely been revised We assert that this may cause confusion about two of the main concepts: fixations and saccades In this study, we assessed the definitions of fixations and saccades held in the eye-movement field, by surveying 124 eye-movement researchers These eye-movement researchers held a variety of definitions of fixations and saccades, of which the breadth seems even wider than what is reported in the literature Moreover, these definitions did not seem to be related to researcher background or experience We urge researchers to make their definitions more explicit by specifying all the relevant components of the eye movement under investigation: (i) the oculomotor component: eg whether the eye moves slow or fast; (ii) the functional component: what purposes does the eye movement (or lack thereof) serve; (iii) the coordinate system used: relative to what does the eye move; (iv) the computational definition: how is the event represented in the eye-tracker signal This should enable eye-movement researchers from different fields to have a discussion without misunderstandings

The 'Real-World Approach' and Its Problems: A Critique of the Term Ecological Validity.

Abstract: A popular goal in psychological science is to understand human cognition and behavior in the 'real-world.' In contrast, researchers have typically conducted their research in experimental research settings, a.k.a. the 'psychologist's laboratory.' Critics have often questioned whether psychology's laboratory experiments permit generalizable results. This is known as the 'real-world or the lab'-dilemma. To bridge the gap between lab and life, many researchers have called for experiments with more 'ecological validity' to ensure that experiments more closely resemble and generalize to the 'real-world.' However, researchers seldom explain what they mean with this term, nor how more ecological validity should be achieved. In our opinion, the popular concept of ecological validity is ill-formed, lacks specificity, and falls short of addressing the problem of generalizability. To move beyond the 'real-world or the lab'-dilemma, we believe that researchers in psychological science should always specify the particular context of cognitive and behavioral functioning in which they are interested, instead of advocating that experiments should be more 'ecologically valid' in order to generalize to the 'real-world.' We believe this will be a more constructive way to uncover the context-specific and context-generic principles of cognition and behavior.

Noise-robust fixation detection in eye movement data : Identification by two-means clustering (I2MC)

Abstract: Eye-tracking research in infants and older children has gained a lot of momentum over the last decades Although eye-tracking research in these participant groups has become easier with the advance of the remote eye-tracker, this often comes at the cost of poorer data quality than in research with well-trained adults (Hessels, Andersson, Hooge, Nystrom, & Kemner Infancy, 20, 601-633, 2015; Wass, Forssman, & Leppanen Infancy, 19, 427-460, 2014) Current fixation detection algorithms are not built for data from infants and young children As a result, some researchers have even turned to hand correction of fixation detections (Saez de Urabain, Johnson, & Smith Behavior Research Methods, 47, 53-72, 2015) Here we introduce a fixation detection algorithm-identification by two-means clustering (I2MC)-built specifically for data across a wide range of noise levels and when periods of data loss may occur We evaluated the I2MC algorithm against seven state-of-the-art event detection algorithms, and report that the I2MC algorithm's output is the most robust to high noise and data loss levels The algorithm is automatic, works offline, and is suitable for eye-tracking data recorded with remote or tower-mounted eye-trackers using static stimuli In addition to application of the I2MC algorithm in eye-tracking research with infants, school children, and certain patient groups, the I2MC algorithm also may be useful when the noise and data loss levels are markedly different between trials, participants, or time points (eg, longitudinal research)

The Perception of the Visual World. By James J. Gibson. U.S.A.: Houghton Mifflin Company, 1950 (George Allen & Unwin, Ltd., London). Price 35s.

Abstract: Let's read! We will often find out this sentence everywhere. When still being a kid, mom used to order us to always read, so did the teacher. Some books are fully read in a week and we need the obligation to support reading. What about now? Do you still love reading? Is reading only for you who have obligation? Absolutely not! We here offer you a new book enPDFd the perception of the visual world to read.

Anxiety in high functioning children with autism

Abstract: High-functioning children with autism were compared with two control groups on measures of anxiety and social worries. Comparison control groups consisted of children with specific language impairment (SLI) and normally developing children. Each group consisted of 15 children between the ages of 8 and 12 years and were matched for age and gender. Children with autism were found to be most anxious on both measures. High anxiety subscale scores for the autism group were separation anxiety and obsessive-compulsive disorder. These findings are discussed within the context of theories of autism and anxiety in the general population of children. Suggestions for future research are made.

Five factors that guide attention in visual search

Abstract: How do we find what we are looking for? Even when the desired target is in the current field of view, we need to search because fundamental limits on visual processing make it impossible to recognize everything at once. Searching involves directing attention to objects that might be the target. This deployment of attention is not random. It is guided to the most promising items and locations by five factors discussed here: bottom-up salience, top-down feature guidance, scene structure and meaning, the previous history of search over timescales ranging from milliseconds to years, and the relative value of the targets and distractors. Modern theories of visual search need to incorporate all five factors and specify how these factors combine to shape search behaviour. An understanding of the rules of guidance can be used to improve the accuracy and efficiency of socially important search tasks, from security screening to medical image perception. How do we find what we are looking for? Wolfe and Horowitz discuss the five factors that guide attention in visual search.

Constructing the subject: historical origins of psychological research.

Abstract: effective prevention campaigns. This is the \"lesson of history\" used to argue for a liberal policy approach. The book is not a work of original scholarship. Clark is bringing together a body of historical and current writing about AIDS and epidemic disease, much of which is familiar. Despite his historical analysis of widely different cultures, his focus in the present is almost entirely on the United States and the impact of AIDS in that particular culture. Even within the U.S., he takes no account of more recent disease formulations, such as the \"chronic disease\" model, which has been widely discussed. AIDS, whether rightly or wrongly, is no longer seen within the epidemic model; it would have been helpful to have some consideration of those more recent changes. Outside the U.S., too, AIDS has been a much less powerful force for the reform of health care systems. In the U.K., for example, AIDS funding has been the victim of recent health service changes rather than a driving force for change. The book is therefore of limited relevance to a non-American audience, although it is well produced and illustrated by thirteen full colour plates, ranging from a 1350 representation of Saint Sebastian to the AIDS quilt in the 1990s.