An adaptive algorithm for fixation,saccade, and glissade detection in eyetracking data

Event detection is used to classify recorded gaze points into periods of fixation, saccade, smooth pursuit, blink, and noise. Although there is an overall consensus that current algorithms for event detection have serious flaws and that a de facto standard for event detection does not exist, surprisingly little work has been done to remedy this problem. We suggest a new velocity-based algorithm that takes several of the previously known limitations into account. Most important, the new algorithm identifies so-called glissades, a wobbling movement at the end of many saccades, as a separate class of eye movements. Part of the solution involves designing an adaptive velocity threshold that makes the event detection less sensitive to variations in noise level and the algorithm settings-free for the user. We demonstrate the performance of the new algorithm on eye movements recorded during reading and scene perception and compare it with two of the most commonly used algorithms today. Results show that, unlike the currently used algorithms, fixations, saccades, and glissades are robustly identified by the new algorithm. Using this algorithm, we found that glissades occur in about half of the saccades, during both reading and scene perception, and that they have an average duration close to 24 msec. Due to the high prevalence and long durations of glissades, we argue that researchers must actively choose whether to assign the glissades to saccades or fixations; the choice affects dependent variables such as fixation and saccade duration significantly. Current algorithms do not offer this choice, and their assignments of each glissade are largely arbitrary.     

Sex differences in left-handedness: a meta-analysis of 144 studies

Human handedness, a marker for language lateralization in the brain, continues to attract great research interest. A widely reported but not universal finding is a greater male tendency toward left-handedness. Here the authors present a meta-analysis of k = 144 studies, totaling N = 1,787,629 participants, the results of which demonstrate that the sex difference is both significant and robust. The overall best estimate for the male to female odds ratio was 1.23 (95% confidence interval = 1.19, 1.27). The widespread observation of this sex difference is consistent with it being related to innate characteristics of sexual differentiation, and its observed magnitude places an important constraint on current theories of handedness. In addition, the size of the sex difference was significantly moderated by the way in which handedness was assessed (by writing hand or by other means), the location of testing, and the year of publication of the study, implicating additional influences on its development.     

INTENTIONALISM AND THE IMAGINABILITY OF THE INVERTED SPECTRUM

Various thought-experiments have been offered as independent support for the possibility of intentionalism-defeating spectrum inversion, but they do not succeed. I refute what I take to be the four best arguments for holding that the thought-experiments do in fact provide such support: the implausible error argument, the symmetry argument, the no-inference argument and the best theory of representation argument. I thus offer a defence of intentionalism against a long-standing objection.     

Using a virtual reality system to study balance and walking in a virtual outdoor environment: a pilot study.

Falls and fall-related injuries are a major problem for elderly persons. Most falls occur during walking and turning, and the risk of falling increases when attention is diverted to something besides walking. It is often difficult to standardize methods for testing balance and fall tendency in a clinically relevant setting. We describe the development of a system using a virtual environment (VE) to assess how attention demanding and unexpected events influence a person's capacity to control balance and movement. The hardware in the system consists of a head-mounted display (HMD), a magnetic tracker system, and two SGI computers. The software consists of the image generation of the VE and the management and visualization of motion tracking data. In a preliminary pilot study eight subjects (age 23-80) participated. Each subject walked on a normal floor and was visually presented a familiar outdoor environment in the HMD. They were exposed to different unexpected events, such as a virtual snowfall and tilting of the VE. Disturbances of balance and walking patterns such as changes in speed, stride length and balance reactions like slipping were observed. Two subjects experienced symptoms of cyber sickness with a SSQ score above 25 points. Walking with sensors only did not affect walking time, but in VE the subjects generally walked more slowly. Virtual tilting of the environment had an impact on balance performance during walking. This effect was not observed while the test subjects were walking in a virtual snowfall. The model needs further development but may hold a potential for clinical use.     

“For a New World”: On the practical impulse of Husserlian theory

The thesis of this article is that in Husserlian phenomenology there is no opposition between theory and praxis. On the contrary, he understands the former to serve the latter, so as to usher in a new world. The means for doing is the phenomenological reduction or epoché. It gives the phenomenologist access to the starting point, the “first things,” and orients his/her striving towards reason and the renewal of humanity. Careful attention to the significance of the epoché also sheds light on Husserl’s understanding of the relationship of phenomenology not only to philosophy but also to the other sciences. Though an exposition of the “phenomenology of the philosophical vocation” which Husserl sketched in the 1920s, e.g., in his Kaizo articles and lectures on first philosophy, the author seeks to shore up his thesis. For Walter Biemel     

Errors, efficiency, and the interplay between attention and category learning

Learning to identify objects as members of categories is an essential cognitive skill and learning to deploy attention effectively is a core component of that process. The present study investigated an assumption imbedded in formal models of categorization: error is necessary for attentional learning. Eye-trackers were used to record participants’ allocation of attention to task relevant and irrelevant features while learning a complex categorization task. It was found that participants optimized their fixation patterns in the absence of both performance errors and corrective external feedback. Optimization began immediately after each category was mastered and continued for many trials. These results demonstrate that error is neither necessary nor sufficient for all forms of attentional learning.     

Asymmetric cost and benefit perceptions in willingness-to-donate decisions

Charitable giving entails the act of foregoing personal resources in order to improve the conditions of other people. In the present paper, we systematically examine two dimensions integral to donation decisions that have thus far received relatively little attention but can explain charitable behavior rather well: the perceptions of cost for the donor and benefit for the recipients. In line with current theories in judgment and decision making, we hypothesize that people weigh these dimensions subjectively and perceive them asymmetrically, consistent with prospect theory. Costs for the donor are typically perceived as losses, whereas benefits for recipients are perceived as gains. In four studies, we presented several scenarios to participants in which both donation amounts (costs) and number of lives helped (benefits) were manipulated while keeping the ratio of costs and benefits constant. Results from Studies 1 and 2 showed that willingness to help decreased as donation amounts and number of lives helped increased. Additionally, Studies 3 and 4 provide evidence for a solution to reduce the asymmetry and increase donation amounts as the number of lives at risk increases.