Cleaning up systematic error in eye-tracking data by using required fixation locations

In the course of running an eye-tracking experiment, one computer system or subsystem typically presents the stimuli to the participant and records manual responses, and another collects the eye movement data, with little interaction between the two during the course of the experiment. This article demonstrates how the two systems can interact with each other to facilitate a richer set of experimental designs and applications and to produce more accurate eye tracking data. In an eye-tracking study, a participant is periodically instructed to look at specific screen locations, orexplicit required fixation locations (RFLs), in order to calibrate the eye tracker to the participant. The design of an experimental procedure will also often produce a number ofimplicit RFLs—screen locations that the participant must look at within a certain window of time or at a certain moment in order to successfully and correctly accomplish a task, but without explicit instructions to fixate those locations. In these windows of time or at these moments, the disparity between the fixations recorded by the eye tracker and the screen locations corresponding to implicit RFLs can be examined, and the results of the comparison can be used for a variety of purposes. This article shows how the disparity can be used to monitor the deterioration in the accuracy of the eye tracker calibration and to automatically invoke a re-calibration procedure when necessary. This article also demonstrates how the disparity will vary across screen regions and participants and how each participant’s uniqueerror signature can be used to reduce the systematic error in the eye movement data collected for that participant.     

Action relations, semantic relations, and familiarity of spatial position in Balint’s syndrome: Crossover effects on perceptual report and on localization

We contrasted effects of the action relationship between objects, relative to effects of semantic relation and familiarity of spatial location, in a patient with Balint’s syndrome. We found enhanced perceptual report of objects placed in the correct colocations for action in comparison with when the objects (1) were placed in incorrect locations for action (Experiment 1), (2) were associatively related (Experiment 2), or (3) fell in familiar locations but were not action related (Experiment 4). In contrast, the ability to localize the objects was affected by whether the objects were in familiar as opposed to unfamiliar locations with respect to one another. Action relations between objects facilitate joint attention to both objects but do not facilitate binding to location. Familiar spatial relations facilitate spatial binding, but do not cue joint attention to the stimuli. Effects of action relation on attention and localization can be dissociated from effects of semantic relationship and familiarity of spatial location on attention and localization.     

The modulation of lexical competition by segment duration

In an eye-tracking study, we examined how fine-grained phonetic detail, such as segment duration, influences the lexical competition process during spoken word recognition. Dutch listeners’ eye movements to pictures of four objects were monitored as they heard sentences in which a stop-initial target word (e.g.,pijp “pipe”) was preceded by an [s]. The participants made more fixations to pictures of cluster-initial words (e.g.,spijker “nail”) when they heard a long [s] (mean duration, 103 msec) than when they heard a short [s] (mean duration, 73 msec). Conversely, the participants made more fixations to pictures of the stop-initial words when they heard a short [s] than when they heard a long [s]. Lexical competition between stop- and cluster-initial words, therefore, is modulated by segment duration differences of only 30 msec.     

Adults’ number-line estimation strategies: Evidence from eye movements

Although the development of number-line estimation ability is well documented, little is known of the processes underlying successful estimators’ mappings of numerical information onto spatial representations during these tasks. We tracked adults’ eye movements during a number-line estimation task to investigate the processes underlying number-to-space translation, with three main results. First, eye movements were strongly related to the target number’s location, and early processing measures directly predicted later estimation performance. Second, fixations and estimates were influenced by the size of the first number presented, indicating that adults calibrate their estimates online. Third, adults’ number-line estimates demonstrated patterns of error consistent with the predictions of psychophysical models of proportion estimation, and eye movement data predicted the specific error patterns we observed. These results support proportion-based accounts of number-line estimation and suggest that adults’ translation of numerical information into spatial representations is a rapid, online process.     

Gaze cuing and affective judgments of objects: I like what you look at

When we see another person look somewhere, we automatically attend to the same location in space. Thisjoint attention emerges early in life and has a great impact on social interactions in development and in everyday adult life. The direction of another’s gaze indicates what object is of current interest, which may be the target for a subsequent action. In this study, we found that objects that are looked at by other people are liked more than objects that do not receive the attention of other people (Experiment 1). This suggests that observing averted gaze can have an impact on the affective appraisals of objects in the environment. This liking effect was absent when an arrow was used to cue attention (Experiment 2). This underlines the importance of other people’s interactions with objects for generating our own impressions of such stimuli in the world.     

Different mental representations for place recognition and goal localization

Determining one’s current location and locating a goal relative to one’s position are important components of successful human navigation in familiar environments. Several prominent cognitive theories of human spatial memory (e.g., McNamara, 2003; Sholl, 2001; Wang & Spelke, 2002) assume that both behaviors access the same enduring mental representations of the environment. Participants in the present experiment learned the locations of seven objects within a room from two views, and were then tested in a separate room using scene recognition and judgments of relative direction (JRD). Scene recognition results indicated that two viewer-centered representations of the layout of objects were preserved in long-term memory, whereas JRD showed evidence of a single orientation-dependent long-term mental representation. The challenges of incorporating the present findings into existing theories of human spatial memory are discussed.     

Spatial updating relies on an egocentric representation of space: Effects of the number of objects

Models of spatial updating attempt to explain how representations of spatial relationships between the actor and objects in the environment change as the actor moves. In allocentric models, object locations are encoded in an external reference frame, and only the actor’s position and orientation in that reference frame need to be updated. Thus, spatial updating should be independent of the number of objects in the environment (set size). In egocentric updating models, object locations are encoded relative to the actor, so the location of each object relative to the actor must be updated as the actor moves. Thus, spatial updating efficiency should depend on set size. We examined which model better accounts for human spatial updating by having people reconstruct the locations of varying numbers of virtual objects either from the original study position or from a changed viewing position. In consistency with the egocentric updating model, object localization following a viewpoint change was affected by the number of objects in the environment.     

Visual layout modulates Fitts’s law: The importance of first and last positions

When a target in the last position of a structured visual array is aimed for, movement times (MTs) are shorter than predicted by Fitts’s law (Adam, Mol, Pratt, & Fischer, 2006). That study, however, confounded relative target position with absolute target location. To determine whether target position does, indeed, produce changes in the speed-accuracy trade-off function, the present experiment manipulated relative target position (e.g., first or last) independently of absolute target location (e.g., nearest or farthest). This was accomplished by presenting connected placeholders at three adjacent locations from a set of five possible locations (i.e., the middle location could be the first, middle, or last placeholder position in an array). The results of a speeded manual-pointing task showed that relative position is important for Fitts’s law; when absolute location was held constant, shorter MTs were found for last-position than for middle-position targets. In addition, a similar effect was found for first-position targets. These results suggest that Fitts’s law holds within, but not between, relative target positions in visible structured arrays.     

Scene context influences without scene gist: Eye movements guided by spatial associations in visual search

Although the use of semantic information about the world seems ubiquitous in every task we perform, it is not clear whether we rely on a scene’s semantic information to guide attention when searching for something in a specific scene context (e.g., keys in one’s living room). To address this question, we compared contribution of a scene’s semantic information (i.e., scene gist) versus learned spatial associations between objects and context. Using the flash-preview–moving-window paradigm Castelhano and Henderson (Journal of Experimental Psychology: Human Perception and Performance 33:753–763, 2007), participants searched for target objects that were placed in either consistent or inconsistent locations and were semantically consistent or inconsistent with the scene gist. The results showed that learned spatial associations were used to guide search even in inconsistent contexts, providing evidence that scene context can affect search performance without consistent scene gist information. We discuss the results in terms of hierarchical organization of top-down influences of scene context.     

Memory for action events in the bottlenosed dolphin

We investigated whether a bottlenosed dolphin’s ability to recall and repeat actions on command would immediately generalize to actions performed with specified objects. The dolphin was tested on her ability to repeat 18 novel behaviors performed with potentially interchangeable objects specified using an artificial gestural language. Such “action events” were correctly repeated at above chance levels, indicating that the dolphin had access to memories of those events. Performance levels were, however, lower than in previous tests. The dolphin appeared to have difficulty recalling which object an action was performed with. Previous research has demonstrated that animals can recall features of their environment and features of their actions independently of one another. The results of this study demonstrate (1) that the dolphin’s concept of repeating extends beyond simply accessing memories of movement patterns, and (2) that dolphins’ memories of past events incorporate representations of both self-performed acts and objects, locations, or gestural instructions. Received:10 October 1998 / Accepted after revision: 22 December 1998     

Eyetracking for two-person tasks with manipulation of a virtual world

Eyetracking facilities are typically restricted to monitoring a single person viewing static images or prerecorded video. In the present article, we describe a system that makes it possible to study visual attention in coordination with other activity during joint action. The software links two eyetracking systems in parallel and provides an on-screen task. By locating eye movements against dynamic screen regions, it permits automatic tracking of moving on-screen objects. Using existing SR technology, the system can also cross-project each participant’s eyetrack and mouse location onto the other’s on-screen work space. Keeping a complete record of eyetrack and on-screen events in the same format as subsequent human coding, the system permits the analysis of multiple modalities. The software offers new approaches to spontaneous multimodal communication: joint action and joint attention. These capacities are demonstrated using an experimental paradigm for cooperative on-screen assembly of a two-dimensional model. The software is available under an open source license.     

Self produced and observed actions influence emotion: the roles of action fluency and eye gaze

Affective responses to objects can be influenced by cognitive processes such as perceptual fluency. Here we investigated whether the quality of motor interaction with an object influences affective response to the object. Participants grasped and moved objects using either a fluent action or a non-fluent action (avoiding an obstacle). Liking ratings were higher for objects in the fluent condition. Two further studies investigated whether the fluency of another person’s actions influences affective response. Observers watched movie clips of the motor actions described above, in conditions where the observed actor could be seen to be looking towards the grasped object, or where the actor’s head and gaze were not visible. Two results were observed: First, when the actor’s gaze cannot be seen, liking ratings of the objects are reduced. Second, action fluency of observed actions does influence liking ratings, but only when the actor’s gaze towards the object is visible. These findings provide supporting evidence for the important role of observed eye gaze in action simulation, and demonstrate that non-emotive actions can evoke empathic states in observers. This research was supported by Economic and Social Research Council grant RES-000-23-0429 awarded to S. P. Tipper and A. E. Hayes.     

Domesticated dogs’ (Canis familiaris) use of the solidity principle

Organisms must often make predictions about the trajectories of moving objects. However, often these objects become hidden. To later locate such objects, the organism must maintain a representation of the object in memory and generate an expectation about where it will later appear. We explored adult dogs’ knowledge and use of the solidity principle (that one solid object cannot pass through another solid object) by evaluating search behavior. Subjects watched as a treat rolled down an inclined tube into a box. The box either did or did not contain a solid wall dividing it in half. To find the treat, subjects had to modify their search behavior based on the presence or absence of the wall, which either did or did not block the treat’s trajectory. Dogs correctly searched the near location when the barrier was present and the far location when the barrier was absent. They displayed this behavior from the first trial, as well as performed correctly when trial types were intermingled. These results suggest that dogs direct their searches in accordance with the solidity principle.     

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.     

Vertical meridian asymmetry in spatial resolution: Visual and attentional factors

We investigated whether spatial resolution would be the same in the lower and upper halves of thevertical meridian (VM) of our visual field and whether attention would affect them differentially. It has been reported that (1) attending to the target’s location improves performance in a texture segregation task when the observer’s spatial resolution is too low (peripheral locations) but impairs it when resolution is already too high (central locations) for the task. This finding indicates an enhanced spatial resolution at the attended location (Yeshurun & Carrasco, 1998, 2000), (2) observers’ contrast sensitivity is higher in the lower than in the upper VM, a phenomenon known asvertical meridian asymmetry (VMA), an asymmetry determined by visual rather than by attentional factors (Carrasco, Talgar, & Cameron, 2001). In the present texture segregation task, performance was assessed under neutral- and peripheralcue conditions. Transient covert attention was systematically manipulated by using a peripheral cue that indicated the target’s location and its onset. Observers reported the interval containing a target patch appearing at one of a number of eccentricities in a large texture pattern along the VM. We found that (1) performance peaked at farther eccentricities in the lower than in the upper visual VM, indicating that resolution was higher in the lower half, and (2) the peripheral cue affected performance along the VM uniformly, indicating that the degree of enhanced resolution brought about by transient attention was constant along the VM. Thus, we conclude that the VMA for spatial resolution is determined by visual, not transient covert attentional, constraints.     

On Visual Experience of Objects: Comments on John Campbell’s<Emphasis Type="Italic">Reference and Consciousness</Emphasis>

John Campbell argues that visual attention to objects is the means by which we can refer to objects, and that this is so because conscious visual attention enables us to retrieve information about a location. It is argued here that while Campbell is right to think that we visually attend to objects, he does not give us sufficient ground for thinking that consciousness is involved, and is wrong to assign an intermediary role to location. Campbell’s view on sortals is also queried, as is his espousal of the so-called Referential View of Experience.     

Some differences between Kant’s and Husserl’s conceptions of transcendental philosophy

This article compares the differences between Kant’s and Husserl’s conceptions of the “transcendental.” It argues that, for Kant, the term “transcendental” stands for what is otherwise called “metaphysical,” i.e. non-empirical knowledge. As opposed to his predecessors, who had believed that such non-empirical knowledge was possible for meta-physical, i.e. transcendent objects, Kant’s contribution was to show how there can be non-empirical (a priori) knowledge not about transcendent objects, but about the necessary conditions for the experience of natural, non-transcendent objects. Hence the transcendental for Kant ends up connoting a philosophy that claims to show how subjective forms of intuition and thinking have objective validity for all objects as appearances. By contrast, Husserl’s phenomenological philosophy takes a different set of problems for its starting point. His quest is to avoid the uncertainty of empirical knowledge about all kinds of objects that present themselves to us as something other than, something transcendent to, consciousness. Transcendental or reliable knowledge is made possible through the phenomenological reduction that focuses strictly on consciousness as immediately self-given to itself—reflection upon “pure” consciousness. The contents of such consciousness are not the same for everyone and at every time, so they are not necessary and invariant in the way that Kant’s pure forms of subjectivity are. Since Husserl however also claims that the all objects, as intentional objects, are constituted in and for consciousness, an investigation into the structures of pure subjectivity can also be called “transcendental” in a further sense of showing the genesis of our knowledge of objects that are transcendent to consciousness. Moreover, since Husserl’s philosophical interest is precisely upon the structures of that consciousness, he also concentrates on necessary conditions for the constitution of these objects in his philosophical work. Hence, there ends up being a great deal of overlap between his own transcendental project and Kant’s in spite of the differences in what each of them means by the term “transcendental.”

SAS and SPSS macros to calculate standardized Cronbach’s alpha using the upper bound of the phi coefficient for dichotomous items

Cronbach’s α is widely used in social science research to estimate the internal consistency of reliability of a measurement scale. However, when items are not strictly parallel, the Cronbach’s α coefficient provides a lower-bound estimate of true reliability, and this estimate may be further biased downward when items are dichotomous. The estimation of standardized Cronbach’s α for a scale with dichotomous items can be improved by using the upper bound of coefficient ϕ. SAS and SPSS macros have been developed in this article to obtain standardized Cronbach’s α via this method. The simulation analysis showed that Cronbach’s α from upper-bound ϕ might be appropriate for estimating the real reliability when standardized Cronbach’s α is problematic.     

Perception of object-context relations: eye-movement analyses in infants and adults

Twenty-eight 4-month-olds' and twenty-two 20-year-olds' attention to object-context relations was investigated using a common eye-movement paradigm. Infants and adults scanned both objects and contexts. Infants showed equivalent preferences for animals and vehicles and for congruent and incongruent object-context relations overall, more fixations of objects in congruent object-context relations, more fixations of contexts in incongruent object-context relations, more fixations of objects than contexts in vehicle scenes, and more fixation shifts in incongruent than congruent vehicle scenes. Adults showed more fixations of congruent than incongruent scenes, vehicles than animals, and objects than contexts; equal fixations of animals and their contexts but more fixations of vehicles than their contexts; and more shifts of fixation when inspecting animals in context than vehicles in context. These findings for location, number, and order of eye movements indicate that object-context relations play a dynamic role in the development and allocation of attention.     

Seeing Meaning: Frege and Derrida on Ideality and the Limits of Husserlian Intuitionism

The article seeks to challenge the standard accounts of how to view the difference between Husserl and Frege on the nature of ideal objects and meanings. It does so partly by using Derrida’s deconstructive reading of Husserl to open up a critical space where the two approaches can be confronted in a new way. Frege’s criticism of Husserl’s philosophy of mathematics (that it was essentially psychologistic) was partly overcome by the program of transcendental phenomenology. But the original challenge to the prospect of a fulfilled intuition of idealities remained and was in fact encountered again from within the transcendental analysis by Husserl himself in his last writings on geometry and language. According to the two standard and conflicting accounts, Husserl either changed his earlier psychologistic program as a result of Frege’s criticism, or he was in fact never challenged by it in the first place. The article shows instead how Husserl continued to struggle with the problem of the constitution of ideal objects, and how his quest led him to a point where his analyses anticipate a more dialectical and deconstructive conclusion, eventually made explicit by Derrida. It also shows not only how this development constitutes a philosophical continuity from the original dispute with Frege, but also how Frege’s critique in a certain respect could be read as an anticipation of Derrida’s deconstructive elaboration of Husserl’s phenomenology.