The Observer: A software system for collection and analysis of observational data

The Observer is a general-purpose software package for event recording and data analysis in behavioral research. It allows any IBM-type personal computer to serve as an event recorder. In addition, The Observer can generate dedicated event-recording programs for several types of non-IBM-compatible portable and hand-held computers and transfer files between the PC and such computers. The user specifies options through menus. The configuration can be either used directly for event recording on the PC or passed on to a program generator that creates a program to collect data on a hand-held computer. Observational data from either type of computer can be analyzed by the program. Event-recording configurations can be tailored to many different experimental designs. Keys can be designated as events, and modifiers can be used to indicate the limits of an event. The program allows grouping of events in classes and distinction between mutually exclusive versus nonexclusive events and duration events versus frequency events. Timing of events is accurate to 0.1 sec. An on-line electronic notepad permits notes to be made during an observation session. The program also includes on-line error correction. User comments as well as independent variables can be stored together with the observational data. During data analysis, the user can select the level of analysis and the type of output file. The Observer calculates frequency of occurrence and duration for classes of events, individual events, or combinations of events. For analysis of concurrence, one can select the number of nesting levels and the order of nesting. Output can be generated in the form of sorted event sequence files, text report files, and tabular ASCII files. The results can be exported to spreadsheet and statistical programs.     

An eye movement analysis system (EMAS) for the identification of cognitive processes on figural tasks

EMAS is a software system (written in VAX-11 FORTRAN) for the analysis of eye movement data recorded during the performance of figural tasks. Its main functions are: (1) Calibration of raw coordinates of eye movements to determine their actual position on the stimulus display. Different kinds of measurement distortion may be corrected. (2) Identification of eye fixations and the determination of their locations and durations. (3) Analysis of fixation sequences. The frequency of transitions of fixations among specified sectors of the stimulus display is computed. A sequential list is made of the successive fixations in which the fixated sector and the fixation duration are graphically indicated. (4) Plotting of raw or calibrated eye movement data and fixation points. The sequence of fixations in specified display sectors can also be plotted in real time. Applications of the programs to the Embedded Figures Test and the Hidden Figures Test are illustrated.     

Mode-of-disparities error correction of eye-tracking data

In eye-tracking research, there is almost always a disparity between a person’s actual gaze location and the location recorded by the eye tracker. Disparities that are constant over time are systematic error. In this article, we propose an error correction method that can reliably reduce systematic error and restore fixations to their true locations. We show that the method is reliable when the visual objects in the experiment are arranged in an irregular manner—for example, when they are not on a grid in which all fixations can be shifted to adjacent locations using the same directional adjustment. The method first calculates the disparities between fixations and their nearest objects. It then uses the annealed mean shift algorithm to find the mode of the disparities. The mode is demonstrated to correctly capture the magnitude and direction of the systematic error so that it can be removed. This article presents the method, an extended demonstration, and a validation of the method’s efficacy.     

Not fixating at the line of text comes at a cost

Previous research on eye guidance in reading has investigated systematic tendencies with respect to horizontal fixation locations on letters within words and the relationship between fixation location in a word and the duration of the fixation. The present study investigates where readers place their eyes vertically on the line of text and how vertical fixation location is related to fixation duration. Analyses were based on a large corpus of eye movement recordings from single-sentence reading. The vertical preferred viewing location was found to be within the vertical extent of the font, but fixations beyond the vertical boundaries of the text also frequently occurred. Analyzing fixation duration as a function of vertical fixation location revealed a vertical optimal viewing position (vOVP) effect: Fixations were shortest when placed optimally on the line of text, and fixation duration gradually increased for fixations that fell above or below the line of text. The vOVP effect can be explained by the limits of visual resolution along the vertical meridian. It is concluded that vertical and horizontal landing positions in single-sentence reading are associated with differences in fixation durations in opposite ways.     

Reduction and calibration of eye monitor data

The present paper presents FORTRAN programs for reducing eye monitor output to fixations and for mapping these fixations to locations in the stimulus space. Flexible parameters of the fixations program allow for determination of the beginning and end of fixations under different resolution criteria and for indicating loss of accurate measurement. The calibration program is based on a rectangular 9-point fixation grid. Each fixation is rescaled within this grid by solving for a quadratic equation. The rescaled values are output in a flexibly determined rectangular coordinate system that is related to the stimulus space, such as character position on the screen. The programs were developed for the 60-Hz Applied Sciences corneal reflection eye monitor, but they may be used with a number of other systems.     

A rapid effect of stimulus quality on the durations of individual fixations during reading

We developed a variant of the single fixation replacement paradigm (Yang & McConkie, 2001, 2004) in order to examine the effect of stimulus quality on fixation duration during reading. Subjects' eye movements were monitored while they read passages of text for comprehension. During critical fixations, equal changes to the luminance of the background produced either an increase (Up-Contrast) or a decrease (Down-Contrast) of the contrast of the text. The durations of critical fixations were found to be lengthened in the Down-Contrast but not the Up-Contrast condition. Ex-Gaussian modelling of the distributions of fixation durations showed that the reduction in stimulus quality lengthened the majority of fixations, and a survival analysis estimated the onset of this effect to be approximately 141 ms following fixation onset. Because the stimulus quality of the text during critical fixations could not be predicted or parafoveally previewed prior to foveation, the present effect can be attributed to an immediate effect of stimulus quality on fixation duration.     

Information influences the pattern of eye fixations during sentence comprehension

How does the pattern of eye fixation vary as an informative part of a word is encountered? If the processing of information lags behind the movement of the eyes, then we should expect no variation in the pattern; but if processing is immediate, then the movements of the reader's eyes should correspond to the distribution of information being inspected. An experiment is reported which examined the ways that the text ahead of the point of current fixation can be used to guide the eyes to future fixations, by monitoring fixations during a sentence comprehension task. The patterns of eye fixations upon words with uneven distributions of information (where, for example, words predictable from the sight of their first few letters but not from their last few letters are defined as containing informative beginnings) were observed, and it was found that more and longer fixations were produced when subjects looked at the informative parts of words, particularly at the informative endings of words. The results support the suggestion that eye movements are under the moment-to-moment control of cognitive mechanisms.     

What children are looking at during shared storybook reading

Two studies were conducted to determine the extent to which young children fixate on the print of storybooks during shared book reading. Children's books varying in the layout of the print and the richness of the illustrations were displayed on a computer monitor. Each child's mother or preschool teacher read the books while the child sat on the adult's lap wearing an EyeLink headband that recorded visual fixations. In both studies, children spent very little time examining the print regardless of the nature of the print and illustrations. Although fixations on the illustrations were highly correlated with the length of the accompanying text and could be altered by altering the content of the text, fixations to the text were uncorrelated with the length of the text. These results indicate that preschool children engage in minimal exploration of the print during shared book reading.     

ASTEF: A simple tool for examining fixations

In human factors and ergonomics research, the analysis of eye movements has gained popularity as a method for obtaining information concerning the operator's cognitive strategies and for drawing inferences about the cognitive state of an individual. For example, recent studies have shown that the distribution of eye fixations is sensitive to variations in mental workload---dispersed when workload is high, and clustered when workload is low. Spatial statistics algorithms can be used to obtain information about the type of distribution and can be applied over fixations recorded during small epochs of time to assess online changes in the level of mental load experienced by the individuals. In order to ease the computation of the statistical index and to encourage research on the spatial properties of visual scanning, A Simple Tool for Examining Fixations has been developed. The software application implements functions for fixation visualization, management, and analysis, and includes a tool for fixation identification from raw gaze point data. Updated information can be obtained online at www.astef.info, where the installation package is freely downloadable.     

Towards an express-diagnostics for level of processing and hazard perception

The analysis of eye movements can provide rich information about driver's attention and the course of behaviour in hazardous situations. We present data from a driving simulation study showing that the switching between preattentive and attentive processing is reflected in visual fixations. For this initial analysis, we considered fixations from the perspective of their duration and the amplitude of related saccades. Since fixation durations may change instantaneously from one fixation to the next, we further selected the temporal vicinity of the emerging hazard for a closer analysis of fixations around this time. With this second type of analysis, the fixations that actually “detect” a critical event can be discovered and their duration measured. Upon detection of an immediate hazard, there is an increase in fixation duration and a corresponding increase in occurrence of attentive fixations on the cost of preattentive ones. This switching from one level of processing to another is recognisable on a short, phasic time scale. We finally discuss attentional conditions where overlooked or not sufficiently processed hazards do not lead to the appropriate breaking reaction on the part of the driver.     

Word frequency and predictability effects in reading French: An evaluation of the E-Z Reader model

French readers' eye movements were monitored as they read a passage of text. Initial global analyses of word frequency, accounting for the majority of fixations in the text, revealed a good fit between the observed data and the simulated data from the E-Z Reader 7 model of eye movement control. However, the model did not perform as well on simulations of contextual predictability effects. A subset of 20 controlled words from the passage were used to examine the combined effects of frequency and predictability. Results from the observed data showed main effects of frequency and predictability but no interaction. With certain modifications, the E-Z Reader 7 model was able to adequately simulate the pattern of data. Although the E-Z Reader model successfully accounted for the present data, we believe that further modifications will be necessary in order to better account for data in the literature.     

Time course of visual information utilization during fixations in reading

College students read short texts from a cathode-ray tube as their eye movements were being monitored. During selected fixations, the text was briefly masked and then it reappeared with one word changed. Subjects often were unaware that the word had changed. Sometimes they reported seeing the first presented word, sometimes the second presented word, and sometimes both. When only one word was reported, two factors were found to determine which one it was: the length of time a word was present during the fixation and the predictability of a word in its context. The results suggested that visual information is utilized for reading at a crucial period during the fixation and that this crucial period can occur at different times on different fixations. The pattern of responses suggested that the first letter of a word is not utilized before other letters and that letters are not scanned from left to right during a fixation.     

Reading Text Under Normal and Disappearing Presentation Conditions

InthispaperIwillsummariseaseriesofex鄄perimentsinwhichwe[1,2]investigatedwhetheritwaspossibletoinducea"gapeffect"duringreadingandtoexaminehowwellpeoplecanreadwhenthetextliterallydisappearsfrominfrontoftheireyes.Tocarryouttheworkwerecordedreaders'eyemovementsandemployedanovelsac鄄cadecontingentchangetechniqueinwhichwemadethewordthatthereaderwasfixatingdisap鄄pear60msafterfixationonset.Inadditiontoin鄄vestigatingwhetheragapeffectmightoccurduringreading,thisworkalsoinvestigatedwhethertheprimaryde…     

A computer system for processing eye-movement records

A computer system using the LINC-8 computer was developed to process eye-movement records from two 16-mm cine film input sources : the Mackworth stand camera and the Mackworth wide-angle camera. Data reduction was accomplished by projecting the films onto an X-Y plotting table. An operator marked, using a cursor, either the eyespot, in the case of the stand camera, or the pupil and display center, in the case of the wide-angle camera, in order to digitize the locus of the gaze. This information was normalized and stored on magnetic tape as: ordinal fixation number, fixation duration, and fixation coordinates (X and Y). A software library was created to analyze the three eye-movement measures. One program calculates interfixation distance, fixation time, and dispersion of fixations about a point. A second program operates on data matrices to: calculate area covered by a fixation pattern, frequency of redundant fixations in a fixation pattern, and distribution of fixations over features of the visual display. Data are displayed on either scope or the Calcomp plotter.     

Signal-processing software for teaching and research in psychoacoustics under UNIX and X-Windows

A package of software is described that generates, analyzes, stores, and displays sampled waveforms. The package is designed for use under UNIX and includes C source code, UNIX manual pages, and tutorial documents. The programs interact via UNIX pipes using an ASCII-text data format, which enables the user to view the data in numerical form as well as through the use of plotting programs. Among many other functions, the programs can do the following: efficiently generate linearphase FIR filters with arbitrary transfer functions; generate impulse responses for rectangular rooms of specified dimensions; convolve waveforms with each other; perform Fourier transformation and inverse Fourier transformation; filter waveforms in the Fourier domain; filter waveforms according to the peripheral frequency selectivity of the human auditory system; cross-correlate waveforms; autocorrelate waveforms; synthesize complex waveforms, including vowel sounds and white noise. The software can read and write a variety of commonly used waveform file formats. The data can be plotted on an X-Window display using thegnuplot software, which has been included in the package. The complete software package is available via anonymous ftp from ftp.ihr.mrc.ac.uk in ~ftp/pub/johncu/wave.tar.Z     

词边界信息对读者阅读歧义短语时眼跳策略的影响

采用Eye Link 2000眼动仪,选取60个歧义短语,要求大学生被试阅读包含有歧义短语的句子。句子的呈现设置了四种条件:正常无阴影、词间阴影、歧义阴影和字间阴影,以探讨词边界信息是否影响读者阅读歧义短语时的注视位置效应。结果发现:读者对歧义短语的首次注视位置在四种条件下基本一致;词边界信息影响读者对歧义短语的再注视概率。结果表明,词边界信息对歧义短语的影响主要体现在眼跳行动(即"where")的晚期阶段。     

话题兴趣与文本阅读眼动特征的研究

以大学生为被试,用ASL504型眼动仪,探讨话题兴趣对文本阅读过程眼动特征和文本阅读理解的影响。结果表明：(1)话题兴趣促进深层理解,而不能促进表层理解。(2)话题兴趣主要与阅读时间和注视点数相关联,而与阅读效率无关。(3)文本阅读过程中,阅读时间、注视点数两项眼动指标存在显著的性别差异。