Kenneth Holmqvist

Nicolaus Copernicus University; Universität Regensburg; University of the Free State

Pupil–corneal reflection (P–CR) eye tracking has gained a prominent role in studying dog visual cognition, despite methodological challenges that often lead to lower-quality data than when recording from humans. In the current study, we investigated if and how the morphology of dogs might interfere with tracking of P–CR systems, and to what extent...

Pupil-corneal reflection (P--CR) eye-tracking has gained a prominent role in studying dog visual cognition, despite methodological challenges that often lead to lower quality data than when recording from humans. In the current study, we investigated if and how the morphology of dogs might interfere with tracking of P--CR systems, and to what exte...

In this paper, we present a review of how the various aspects of any study using an eye tracker (such as the instrument, methodology, environment, participant, etc.) affect the quality of the recorded eye-tracking data and the obtained eye-movement and gaze measures. We take this review to represent the empirical foundation for reporting guidelines...

To date most of our knowledge on professional vision has relied on verbal data or questionnaires that used classroom videos as prompts. This has been used to tell us about a teacher’s professional vision. Recently, however, new studies explore professional vision during the act of teaching through the use of mobile eye-tracking. This novel approach...

We empirically investigate the role of small, almost imperceptible balance and breathing movements of the head on the level and colour of noise in data from five commercial video-based P-CR eye trackers. By comparing noise from recordings with completely static artificial eyes to noise from recordings where the artificial eyes are worn by humans, w...

We present an algorithmic method for aligning recall fixations with encoding fixations, to be used in looking-at-nothing paradigms that either record recall eye movements during silence or want to speed up data analysis with recordings of recall data during speech. The algorithm utilizes a novel consensus-based elastic matching algorithm to estimat...

Reading students’ faces and their body language, checking their worksheets, and keeping eye contact is a key trait of teacher competence. The new technology of mobile eye-tracking provides researchers with possibilities to explore teaching from the viewpoint of teacher gaze, but also introduces many new method questions. This study had the primary...

When retrieving image from memory, humans usually move their eyes spontaneously as if the image were in front of them. Such eye movements correlate strongly with the spatial layout of the recalled image content and function as memory cues facilitating the retrieval procedure. However, how close the correlation is between imagery eye movements and t...

Recently, Friedman (2020) published a letter in which he claims there are three errors and two problems in our paper “gazeNet: End-to-end eye-movement event detection with deep neural networks” (Zemblys et al., 2019). Here we respond to these claims by Friedman, namely that improper data were used for Zemblys et al., (2019) and that performance was...

Eye trackers are sometimes used to study the miniature eye movements such as drift that occur while observers fixate a static location on a screen. Specifically, analysis of such eye-tracking data can be performed by examining the temporal spectrum composition of the recorded gaze position signal, allowing to assess its color. However, not only rot...

The magnitude of variation in the gaze position signals recorded by an eye tracker, also known as its precision, is an important aspect of an eye tracker’s data quality. However, data quality of eye-tracking signals is still poorly understood. In this paper, we therefore investigate the following: (1) How do the various available measures character...

Small eye movements (< around 2°) are erroneously measured by video-based P-CR eye-trackers. Can this be remedied? The DPI measures small saccades correctly, but is it an eye-tracker for the future? We present a new eye-tracker, the EWET1, and benchmark against the DPI and the Tobii Spectrum.

We benchmark a new hybrid eye-tracker system against the DPI (Dual Purkinje Imaging) tracker and the Tobii Spectrum in a series of three experiments. In a first within-subjects battery of tests, we show that the precision of the new eye-tracker is much better than that of both the DPI and the Spectrum, but that accuracy is not better. We also show...

For evaluating whether an eye-tracker is suitable for measuring microsaccades, Poletti & Rucci (2016) propose that a measure called ‘resolution’ could be better than the more established root-mean-square of the sample-to-sample distances (RMS-S2S). Many open questions exist around the resolution measure, however. Resolution needs to be calculated u...

Eye movement of a species reflects the visual behavior strategy that it has adapted to during its evolution. What are eye movements of domestic dogs (Canis lupus familiaris) like? Investigations of dog eye movements per se have not been done, despite the increasing number of visuo-cognitive studies in dogs using eye-tracking systems. To fill this g...

Anotace The paper introduces an eye-tracking study investigating text processing of Czech deaf learners when dealing with an English language textbook page. Eye movements of deaf respondents and hearing controls were recorded when performing a reading comprehension task to determine whether the two groups differ in processing text accompanied by se...

The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergence is generally biased for centrally symmetric erro...

Humans involuntarily move their eyes when retrieving an image from memory. This motion is often similar to actually observing the image. We suggest to exploit this behavior as a new modality in human computer interaction, using the motion of the eyes as a descriptor of the image. Interaction requires the user's eyes to be tracked but no voluntary p...

As large eye-tracking datasets are created, data privacy is a pressing concern for the eye-tracking community. De-identifying data does not guarantee privacy because multiple datasets can be linked for inferences. A common belief is that aggregating individuals' data into composite representations such as heatmaps protects the individual. However,...

Although in real life people frequently perform visual search together, in lab experiments this social dimension is typically left out. Here, we investigate individual, collaborative and competitive visual search with visualization of search partners’ gaze. Participants were instructed to search a grid of Gabor patches while being eye tracked. For...

We provide the first large dataset of human fixations on physical 3D objects presented in varying viewing conditions and made of different materials. Our experimental setup is carefully designed to allow for accurate calibration and measurement. We estimate a mapping from the pair of pupil positions to 3D coordinates in space and register the prese...

Existing event detection algorithms for eye-movement data almost exclusively rely on thresholding one or more hand-crafted signal features, each computed from the stream of raw gaze data. Moreover, this thresholding is largely left for the end user. Here we present and develop gazeNet, a new framework for creating event detectors that do not requir...

Human workers often divide labour on the basis of individual qualities. However, contemporary work on decision-making suggests collaborators value opinions equally, even when they are unequally skilled. We investigated whether this equality bias extends to division of labour in a collaborative game that leverages inter-individual short-term memory...

It has come to our attention that the section "Post-processing: Labeling final events" on page 167 of "Using Machine Learning to Detect Events in Eye-Tracking Data" (Zemblys, Niehorster, Komogortsev, & Holmqvist, 2018) contains an erroneous description of the process by which post-processing was performed.

This study is based on the work of Uwano, Nakamura, Monden and Matsumoto (2006) who tried to identify programmers’ eye movements in source code reviews by using eye tracking technology. The researchers were able to identify certain eye movement patterns but due to the technical limitations of earlier eye tracking systems and a small sample they cou...

For evaluating whether an eye-tracker is suitable for measuring microsaccades, Poletti and Rucci (2015) advocate that the measure ‘resolution’ be used rather than RMS-S2S. Many open questions exist around the resolution measure. Resolution needs to be measured using an artificial eye that can be turned in very small steps. Furthermore, resolution h...

I provide links to the latest versions of the software for SMI eye-trackers. I have just collected and organized, and take not credit for the software itself. This is a service to those who work with SMI eye-trackers

When recalling something you have previously read, to what degree will such episodic remembering activate a situation model of described events versus a memory representation of the text itself? The present study was designed to address this question by recording eye movements of participants who recalled previously read texts while looking at a bl...

More and more researchers are considering the omnibus eye movement sequence-the scanpath-in their studies of visual and cognitive processing (e.g. Ni et al., 2011; von & Vasishth, 2011; Hayes, Petrov, & Sederberg, 2011; Madsen, Larson, Loschky, & Rebello, 2012). However, it remains unclear how recent methods for comparing scanpaths perform in exper...

PISA results show that a considerable number of 15-year-old pupils after 8 to 10 years of schooling have a low level of functional reading literacy, as defined in the PISA framework. While PISA results help identify the level of reading competency, they do not reveal what might be the reasons why some students fail to solve the tasks. One way to ex...

We make 3-5 eye movements per second, and these movements are crucial in helping us deal with the vast amounts of information we encounter in our everyday lives. In recent years, thanks to the development of eye-tracking technology, there has been a growing interest in monitoring and measuring these movements, with a view to understanding how we at...

For all eye movement researchers, selecting the right eye-tracker for their intended research could be made easier if within-subject data quality comparisons across eye-trackers could be made public. In this paper, we use collected raw data from up to 194 participants fixating 49 points on 12 remote and tower-mounted eye-trackers (the DPI Gen 5.5,...

We make 3–5 eye movements per second, and these movements are crucial in helping us deal with the vast amounts of information we encounter in our everyday lives. In recent years, thanks to the development of eye-tracking technology, there has been a growing interest in monitoring and measuring these movements, with a view to understanding how we at...

Eye-tracking research in psychology has grown exponentially over the past decades as equipment has become cheaper and easier to use. The surge in eye-tracking research has not, however, been equaled by a growth in methodological awareness, and practices that are best avoided, have become commonplace. We describe nine threats to the validity of eye-...

The eye-tracking method was used to assess the influence of detailed, colorful illustrations on reading behaviors and learning outcomes. Based on participants’ subjective ratings in a pre-study, we selected eight one-page human anatomy lessons. In the main study, participants learned these eight human anatomy lessons; four were accompanied by detai...

Responsiveness to hypnotic procedures has been related to unusual eye behaviors for centuries. Kallio and collaborators claimed recently that they had found a reliable index for "the hypnotic state" through eye-tracking methods. Whether or not hypnotic responding involves a special state of consciousness has been part of a contentious debate in the...

Existing event detection algorithms for eye-movement data almost exclusively rely on thresholding one or more hand-crafted signal features, each computed from the stream of raw gaze data. Moreover, this thresholding is usually left for the end user. Zemblys et al (2017) present an event detector based on Random Forests, where they show how to train...

Existing precision measures do not adequately describe the magnitude of variability (e.g. noise) in eye-movement data, because they are also affected by the nature of the variability in the signal. For instance, sample-to-sample RMS of an “ant trailing” signal would be low, indicating good precision, while the signal could spread over a large spati...

Event detection is a challenging stage in eye movement data analysis. A major drawback of current event detection methods is that parameters have to be adjusted based on eye movement data quality. Here we show that a fully automated classification of raw gaze samples as belonging to fixations, saccades, or other oculomotor events can be achieved us...

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 participa...

Eye tracking is increasingly being used in Educational Science and so has the interest of the eye tracking community grown in this topic. In this paper we briefly introduce the discipline of Educational Science and why it might be interesting to couple it with eye tracking research. We then introduce three major research areas in Educational Scienc...

Two experiments were conducted to investigate the effects of coaction on saccadic and manual responses. Participants performed the experiments either in a solitary condition or in a group of coactors who performed the same tasks at the same time. In Experiment 1, participants completed a pro- and antisaccade task where they were required to make sa...

Most modern video eye trackers use the p-CR (pupil minus CR) technique to deal with small relative movements between the eye tracker camera and the eye. We question whether the p-CR technique is appropriate to investigate saccade dynamics. In two experiments we investigated the dynamics of pupil, CR and gaze signals obtained from a standard SMI Hi-...

The precision of an eye-tracker is critical to the correct identification of eye movements and their properties. To measure a system’s precision, artificial eyes (AEs) are often used, to exclude eye movements influencing the measurements. A possible issue, however, is that it is virtually impossible to construct AEs with sufficient complexity to fu...

To design an experiment that will yield sufficient power, it is important to understand your measurement device and the data quality it produces. Recent work has provided a complete exposé of eye-tracking data quality as a function of screen location and participant characteristics for a series of popular eye-trackers.These results are however base...

Event detection is a challenging stage in eye movement data analysis. The major drawback of current event detection methods is that parameters have to be adjusted based on eye movement data quality. However, a fully automated classification of raw gaze samples as fixations, saccades or other oculomotor events can be achieved using a machine learnin...

For all eye movement researchers, selecting the right eye-tracker for their intended research could be made easier if within-subject data quality comparisons across eye-trackers could be made public. In this paper, we use collected raw data from up to 194 participants fixating 49 points on 12 remote and tower-mounted eye-trackers (the DPI, SRR EyeL...

Almost all eye-movement researchers use algorithms to parse raw data and detect distinct types of eye movement events, such as fixations, saccades, and pursuit, and then base their results on these. Surprisingly, these algorithms are rarely evaluated. We evaluated the classifications of ten eye-movement event detection algorithms, on data from an S...

An eye-tracking study with 60 native Swedish speakers (18–30 years) was conducted to investigate the positive effects on learning outcomes predicted by the disfluency effect. Subtle low-pass filtering was used as a disfluency manipulation and compared with a control condition using regular text. The text was presented on four separate text presenta...

Event detection depends critically on the precision of the eye tracking data. For instance Holmqvist et al. [2012] showed that varying the precision, mea- sured as RMS, from 0.03◦ to 0.30◦ increases average fix- ation duration by around 200 ms on the same data. It is unclear whether selecting threshold settings in the com- mercial event detection a...

In experiments investigating dynamic tasks, it is often useful to examine eye movement scan patterns. We can present trials repeatedly and compute within-subjects/conditions similarity in order to distinguish between signal and noise in gaze data. To avoid obvious repetitions of trials, filler trials must be added to the experimental protocol, resu...

To examine the influence on performance of sound presentation considered more or less disturbing, distracting, and intrusive, an antisaccade task was used to assess executive control over reflexive eye movements. By examining the latency and proportion of correct eye movements in eight sound presentations for 32 participants (15 female), the effect...

Precision of 12 remote and tower-mounted eye-trackers.

Median accuracy in 12 remote and tower-mounted eye-trackers. Lower is better. Within-subjects data from Holmqvist (2015). Sub is number of participants, n is the total number of data points. A common manufacturer specification is “accuracy is better than 0.5°”

Bubble diameter corresponds to average accuracy data from 194 participants per eye-tracker (Holmqvist, 2015)

Event detection depends critically on the precision of the eye tracking data. It is known that adjusting settings in commercial event detection algorithms can alleviate effects of noise, but not which settings are optimal. Taking real and very precise eye movement data from 36 participants, we have produced artificial trials with 40 different noise...

In this study we examined the effects of animated adverts on children’s online reading. We conducted an eye-tracking experiment with authentic web pages to assess whether (1) advert animation primarily affects overt visual attention, or (2) animated adverts primarily affect text comprehension, or (3) both eye movements and comprehension are affecte...

Sample selection is important for event detection, calibration of eye trackers and data qual- ity assessment from eye movement data. As part of the Cogain EDQ work, we apply six dif- ferent sample selection methods on raw data collected from up to 194 participants fixating 49 points on 12 remote and tower-mounted eye trackers (the DPI, SR EyeLink,...

Twenty-six children in 3rd grade were observed while surfing freely on their favourite websites. Eye movement data were recorded, as well as synchronized screen recordings. Each online advert was analyzed in order to quantify low-level saliency features, such as motion, luminance and edge density. The eye movement data were used to register if the...

Recent research has shown that the pupil signal from video-based eye trackers contains post saccadic oscillations (PSOs). These reflect pupil motion relative to the limbus (Nyström, Hooge, & Holmqvist, 2013). More knowledge about video-based eye tracker signals is essential to allow comparison between the findings obtained from modern systems, and...

OBJECTIVE: The goal of this study was to investigate whether on-topic visual cues can serve as aids for the maintenance of discourse coherence and informativeness in autobiographical narratives of persons with Alzheimer's disease (AD). METHODS: The experiment consisted of three randomized conversation conditions: one without prompts, showing a bla...

Analysis of eye movements recorded with a mobile eye-tracker is difficult since the eye-tracking data are severely affected by simultaneous head and body movements. Automatic analysis methods developed for remote-, and tower-mounted eye-trackers do not take this into account and are therefore not suitable to use for data where also head- and body m...

Background / Purpose: To ascertain how event detection algorithms used to identify fixation and saccade perform on data of varying quality. Main conclusion: Depending on the precision of the data and the event detection paradigm used, the same behaviours can be turned into very different eye movement events and parameters. For validity of eye...