Tobii (Sweden)

Irrespective of the precision, the inaccuracy of a pupil-based eye tracker is about 0.5∘. This paper delves into two factors that potentially increase the inaccuracy of the gaze signal, namely, 1) Pupil-size changes and the pupil-size artefact (PSA) and 2) the putative inability of experienced individuals to precisely refixate a visual target. Experiment 1 utilizes a traditional pupil-CR eye tracker, while Experiment 2 employs a retinal eye tracker, the FreezeEye tracker, eliminating the pupil-based estimation. Results reveal that the PSA significantly affects gaze accuracy, introducing up to 0.5∘ inaccuracies during calibration and validation. Corrections based on the relation between pupil size and apparent gaze shift substantially reduce inaccuracies, underscoring the PSA’s influence on eye-tracking quality. Conversely, Experiment 2 demonstrates humans’ precise refixation abilities, suggesting that the accuracy of the gaze signal is not limited by human refixation inconsistencies.

Estimating the gaze direction with a digital video-based pupil and corneal reflection (P-CR) eye tracker is challenging partly since a video camera is limited in terms of spatial and temporal resolution, and because the captured eye images contain noise. Through computer simulation, we evaluated the localization accuracy of pupil-, and CR centers in the eye image for small eye rotations (≪ 1 deg). Results highlight how inaccuracies in center localization are related to 1) how many pixels the pupil and CR span in the eye camera image, 2) the method to compute the center of the pupil and CRs, and 3) the level of image noise. Our results provide a possible explanation to why the amplitude of small saccades may not be accurately estimated by many currently used video-based eye trackers. We conclude that eye movements with arbitrarily small amplitudes can be accurately estimated using the P-CR eye-tracking principle given that the level of image noise is low and the pupil and CR span enough pixels in the eye camera, or if localization of the CR is based on the intensity values in the eye image instead of a binary representation.

The current study examined the effects of variability on infant event-related potential (ERP) data editing methods. A widespread approach for analyzing infant ERPs is through a trial-by-trial editing process. Researchers identify electroencephalogram (EEG) channels containing artifacts and reject trials that are judged to contain excessive noise. This process can be performed manually by experienced researchers, partially automated by specialized software, or completely automated using an artifact-detection algorithm. Here, we compared the editing process from four different editors-three human experts and an automated algorithm-on the final ERP from an existing infant EEG dataset. Findings reveal that agreement between editors was low, for both the numbers of included trials and of interpolated channels. Critically, variability resulted in differences in the final ERP morphology and in the statistical results of the target ERP that each editor obtained. We also analyzed sources of disagreement by estimating the EEG characteristics that each human editor considered for accepting an ERP trial. In sum, our study reveals significant variability in ERP data editing pipelines, which has important consequences for the final ERP results. These findings represent an important step toward developing best practices for ERP editing methods in infancy research.

Selecting values for fixation filters is a difficult task as not only the specifics of the selected filter algorithm has to be taken into account, but also what it is going to be used for and by whom. In this paper the selection and testing process of values for an I-VT fixation filter algorithm implementation is described.

The paper presents an approach to analyzing food packages based on the eye-tracking analysis of consumers exposed to experimentally designed prototypes of packages based on Rule Developing Experimentation methodology. In addition, the paper analyses emotional reactions to conceptual packages (the respondent had a choice among seven alter- natives, including one 'non-emotion' response). The combined approach allows the researcher and the designer to control the stimuli, presenting known combinations to the respondent leading to the discovery of existing links between what the researcher can do to the stimulus by means of a systematic design, how the eye tracks these changes, and what type of re- sponse the participant in a study might make (e.g., interest, statement of emotion). The paper explores this new interlinked approach working with a popular product, wine in a box.