Fixation classification: how to merge and select fixation candidates

Eye trackers are applied in many research fields (e.g., cognitive science, medicine, marketing research). To give meaning to the eye-tracking data, researchers have a broad choice of classification methods to extract various behaviors (e.g., saccade, blink, fixation) from the gaze signal. There is extensive literature about the different classification algorithms. Surprisingly, not much is known about the effect of fixation and saccade selection rules that are usually (implicitly) applied. We want to answer the following question: What is the impact of the selection-rule parameters (minimal saccade amplitude and minimal fixation duration) on the distribution of fixation durations? To answer this question, we used eye-tracking data with high and low quality and seven different classification algorithms. We conclude that selection rules play an important role in merging and selecting fixation candidates. For eye-tracking data with good-to-moderate precision (RMSD < 0.5∘), the classification algorithm of choice does not matter too much as long as it is sensitive enough and is followed by a rule that selects saccades with amplitudes larger than 1.0∘ and a rule that selects fixations with duration longer than 60 ms. Because of the importance of selection, researchers should always report whether they performed selection and the values of their parameters.

Attention allocation on mobile app interfaces when human interacts with them

With the popularity of smartphones and the pervasion of mobile apps, people spend more and more time to interact with a diversity of apps on their smartphones, especially for young population. This raises a question: how people allocate attention to interfaces of apps during using them. To address this question, we, in this study, designed an experiment with two sessions (i.e., Session1: browsing original interfaces; Session 2: browsing interfaces after removal of colors and background) integrating with an eyetracking system. Attention fixation durations were recorded by an eye-tracker while participants browsed app interfaces. The whole screen of smartphone was divided into four even regions to explore fixation durations. The results revealed that participants gave significantly longer total fixation duration on the bottom left region compared to other regions in the session (1) Longer total fixation duration on the bottom was preserved, but there is no significant difference between left side and right side in the session2. Similar to the finding of total fixation duration, first fixation duration is also predominantly paid on the bottom area of the interface. Moreover, the skill in the use of mobile phone was quantified by assessing familiarity and accuracy of phone operation and was investigated in the association with the fixation durations. We found that first fixation duration of the bottom left region is significantly negatively correlated with the smartphone operation level in the session 1, but there is no significant correlation between them in the session (2) According to the results of ratio exploration, the ratio of the first fixation duration to the total fixation duration is not significantly different between areas of interest for both sessions. The findings of this study provide insights into the attention allocation during browsing app interfaces and are of implications on the design of app interfaces and advertisements as layout can be optimized according to the attention allocation to maximally deliver information.

Gaze correlates of view preference: Comparing natural and urban scenes

When looking out of a window, natural views are usually associated with restorative qualities and are given a higher preference than urban scenes. Previous research has shown that gaze behaviour might differ based on the natural or urban content of views. A lower number of fixations has been associated with the aesthetic evaluation of natural scenes while, when looking at an urban environment, a high preference has been correlated with more exploratory gaze behaviours. To characterise gaze correlates of view preference across natural and urban scenes, we collected and analysed experimental data featuring subjective preference ratings, eye-tracking measures, verbal reasoning associated with preference and nature relatedness scores. Consistent with the literature, our results confirm that natural scenes are more preferred than urban views and that gaze behaviours depend on view type and preference. Observing natural scenes was characterised by lower numbers of fixations and saccades, and longer fixation durations, compared to urban views. However, for both view types, most preferred scenes led to more fixations and saccades. Our findings also showed that nature relatedness may be correlated with visual exploration of scenes. Individual preferences and personality attributes, therefore, should be accounted for in studies on view preference and gaze behaviour.

The Reading Signatures of Agreement Attraction

The comprehension of subject-verb agreement shows “attraction effects,” which reveal that number computations can be derailed by nouns that are grammatically unlicensed to control agreement with a verb. However, previous results are mixed regarding whether attraction affects the processing of grammatical and ungrammatical sentences alike. In a large-sample eye-tracking replication of Lago et al. (2015), we support this “grammaticality asymmetry” by showing that the reading profiles associated with attraction depend on sentence grammaticality. In ungrammatical sentences, attraction affected both fixation durations and regressive eye-movements at the critical disagreeing verb. Meanwhile, both grammatical and ungrammatical sentences showed effects of the attractor noun number prior to the verb, in the first- and second-pass reading of the subject phrase. This contrast suggests that attraction effects in comprehension have at least two different sources: the first reflects verb-triggered processes that operate mainly in ungrammatical sentences. The second source reflects difficulties in the encoding of the subject phrase, which disturb comprehension in both grammatical and ungrammatical sentences.

Romance N Prep N constructions in visual word recognition

N Prep N constructions such as Sp. bicicleta de montaña ‘mountain bike’ are very productive and frequent in Romance languages. They commonly have been classified as syntagmatic compounds that show no orthographic union and exhibit an internal structure that resembles free syntactic structures, such as Sp. libro para niños ‘book for children’. There is no consensus on how to best distinguish lexical from syntactic N Prep N constructions. The present paper presents an explorative eye-tracking study on N Prep N constructions, varying both lexical type (lexical vs. syntactic) and preposition across three languages, French, Spanish and Portuguese. The task of the eye-tracking study was a reading aloud paradigm of the constructions in sentence context. Constructions were fixated on less when more frequent, independent of lexical status. There was also modest evidence that a higher construction frequency afforded shorter total fixation durations, but only for lower deciles of the response distribution. The (construction-initial) head noun also received fewer fixations as construction frequency increased, and also when the head noun was more frequent. The second fixation durations on the head noun also revealed an effect of lexical status, with syntactic constructions receiving shorter fixations at the 5th and 7th deciles. The probability of a fixation on the preposition decreased with preposition frequency, but first fixations on the preposition increased with preposition frequency. The prepositions of Portuguese, the language with the richest inventory of prepositions, received more fixations than the prepositions of French and Spanish. The observed pattern of results is consistent with models of lexical processing in which reading is guided by knowledge of both higher-level constructions and knowledge of key constituents such as the head noun and the preposition.

Effects of Acute Physical Fatigue on Gaze Behavior and Performance During a Badminton Game

In badminton, the ability to quickly gather relevant visual information is one of the most important determinants of performance. However, gaze behavior has never been investigated in a real-game setting (with fatigue), nor related to performance. The aim of this study was to evaluate the effect of fatigue on gaze behavior during a badminton game setting, and to determine the relationship between fatigue, performance and gaze behavior. Nineteen novice badminton players equipped with eye-tracking glasses played two badminton sets: one before and one after a fatiguing task. The duration and number of fixations for each exchange were evaluated for nine areas of interest. Performance in terms of points won or lost and successful strokes was not impacted by fatigue, however fatigue induced more fixations per exchange on two areas of interest (shuttlecock and empty area after the opponent's stroke). Furthermore, two distinct gaze behaviors were found for successful and unsuccessful performance: points won were associated with fixations on the boundary lines and few fixation durations on empty area before the participant's stroke; successful strokes were related to long fixation durations, few fixation durations on empty area and a large number of fixations on the shuttlecock, racket, opponent's upper body and anticipation area. This is the first study to use a mobile eye-tracking system to capture gaze behavior during a real badminton game setting: fatigue induced changes in gaze behavior, and successful and unsuccessful performance were associated with two distinct gaze behaviors.

Effects of Experts’ Annotations on Fashion Designers Apprentices’ Gaze Patterns and Verbalisations

Visual expertise is a fundamental proficiency in many vocations and many questions have risen on the topic, with studies looking at experts and novices differences’ in observation (e.g., radiologists) or at ways to help novices achieve visual expertise (e.g., through annotations). However, most of these studies focus on white-collar professions and overlook vocational ones. For example, observing is uttermost important for fashion designers who spend most of their professional time on visual tasks related to creating patterns and garments or performing alterations. Therefore, this study focuses on trying to convey a professional way to look at images by exposing apprentices to images annotated (e.g., circles) by experts and identifying if their gaze (e.g., fixation durations and gaze coverage) and verbalisations (i.e., images descriptions) are affected. The study was conducted with 38 apprentices that were exposed to sequential sets of images depicting shirts, first non-annotated (pre-test), then annotated for the experimental group and non-annotated for the control group (training 1 and training 2), and finally non-annotated (post-test). Also, in the pre and post-test and in training 2 apprentices had to verbally describe each image. Gaze was recorded with the Tobii X2–60 tracker. Results for fixation durations showed that the experimental group looked longer in the annotated part of the shirt in training 1 and in the shirt’s central part at post-test. However, the experimental group did not cover a significantly larger area of the shirt compared to control and verbalisations show no difference between the groups at post-test.

The Impact of Sex Chromosome Trisomies (XXX, XXY, XYY) on Social Attention and Affect Recognition: A Cross-Sectional Eye Tracking Study

Background About 1:650–1000 children are born with an extra X or Y chromosome (47,XXX; 47,XXY; 47,XYY), which results in a Sex Chromosome Trisomy (SCT). This international cross-sectional study was designed to investigate social attention and affect recognition during early life of children with SCT, with the aim to find indicators for support and treatment. Methods A group of 101 children with SCT (aged 1–7 years old; Mage= 3.7 years) was included in this study, as well as a population-based sample of 98 children without SCT (Mage= 3.7). Social attention was measured using an eye tracking method that quantifies first fixations and fixation durations on eyes of static faces and fixation durations on social information (eyes, faces) in a dynamic paradigm (with two conditions: single face and multiple faces). Affect recognition was measured using the subtest Affect Recognition of the NEPSY-II neuropsychological test battery. Recruitment and assessment took place in the Netherlands and the United States. Results Eyetracking results reveal that children with SCT show lower proportions fixation duration on social information already from the age of three years, compared to children without SCT. Also, impairments in the clinical range for affect recognition were found (32.2% of the SCT group scored in the well below average range); these difficulties increase with age. Conclusions These results highlight the importance to further explore the development of social cognition skills of children with SCT in a longitudinal design, the monitoring of affect recognition skills, and the implementation of (preventive) interventions aiming to support the development of social attention and affect recognition.

Attentional processing of pain faces and other emotional faces in chronic pain–an eye-tracking study

Altered attentional processing of pain-associated stimuli–which might take the form of either avoidance or enhanced vigilance–is thought to be implicated in the development and maintenance of chronic pain. In contrast to reaction time tasks like the dot probe, eye tracking allows for tracking the time course of visual attention and thus differentiating early and late attentional processes. Our study aimed at investigating visual attention to emotional faces in patients with chronic musculoskeletal pain (N = 20) and matched pain-free controls (N = 20). Emotional faces (pain, angry, happy) were presented in pairs with a neutral face for 2000 ms each. Three parameters were determined: First fixation probabilities, fixation durations (overall and divided in four 500 ms intervals) and a fixation bias score as the relative fixation duration of emotional faces compared to neutral faces. There were no group differences in any of the parameters. First fixation probabilities were lower for pain faces than for angry faces. Overall, we found longer fixation duration on emotional compared to neutral faces (‘emotionality bias’), which is in accord with previous research. However, significant longer fixation duration compared to the neutral face was detected only for happy and angry but not for pain faces. In addition, fixation durations as well as bias scores yielded evidence for vigilant-avoidant processing of pain faces in both groups. These results suggest that attentional bias towards pain-associated stimuli might not generally differentiate between healthy individuals and chronic pain patients. Exaggerated attentional bias in patients might occur only under specific circumstances, e.g., towards stimulus material specifically relating to the specific pain of the patients under study or under high emotional distress.