Eye-tracking measures reveal how changes in the design of aided AAC displays influence the efficiency of locating symbols by school-age children without disabilities

Visual fixation patterns to AAC displays are significantly correlated with motor selection for individuals with Down syndrome or individuals on the autism spectrum

Eye tracking research technologies are often used to study how individuals attend visually to different types of AAC displays (e.g. visual scene displays, grid displays). The assumption is that efficiency of visual search may relate to efficiency of motor selection necessary for communication via aided AAC; however, this assumption has not received direct empirical study. We examined the relation between speed of visual search and speed of motor selection of symbols. Ten individuals on the autism spectrum (AS; Study 1) and nine with Down syndrome (DS; Study 2) participated in a search task using simulated AAC displays with a main visual scene display (VSD) and a navigation bar of thumbnail VSDs. Participants were given an auditory prompt to find one of four thumbnail VSDs in the navigation bar. Eye tracking technologies measured how long it took participants to fixate visually on the thumbnail VSD, and recorded how long it took participants to select the thumbnail VSD with a finger. A statistically significant relationship emerged between visual fixation and selection latencies, confirming the positive relationship between visual processing and motor selection for both groups of participants. Eye tracking data may serve as a useful proxy measure for evaluating how display design influences selection of AAC symbols, especially when individuals are unwilling or unable to comply with traditional behaviorally-based assessment tasks.

Use of eye-gaze technology feedback by assistive technology professionals: findings from a thematic analysis

Purpose: Eye-gaze technology offers professionals a range of feedback tools, but it is not well understood how these are used to support decision-making or how professionals understand their purpose and function. This paper explores how professionals use a variety of feedback tools and provides commentary on their current use and ideas for future tool development.Methods and Materials: The study adopted a focus group methodology with two groups of professional participants: those involved in the assessment and provision of eye-gaze technology (n = 6) and those who interact with individuals using eye-gaze technology on an ongoing basis (n = 5). Template analysis was used to provide qualitative insight into the research questions.Results: Professionals highlighted several issues with existing tools and gave suggestions on how these could be made better. It is generally felt that existing tools highlight the existence of problems but offer little in the way of solutions or suggestions. Some differences of opinion related to professional perspective were highlighted. Questions about automating certain processes were raised by both groups.Conclusions: Discussion highlighted the need for different levels of feedback for users and professionals. Professionals agreed that current tools are useful to identify problems but do not offer insight into potential solutions. Some tools are being used to draw inferences about vision and cognition which are not supported by existing literature. New tools may be needed to better meet the needs of professionals and an increased understanding of how existing tools function may support such development.

An Evidence-Based Approach to Augmentative and Alternative Communication Design for Individuals With Cortical Visual Impairment

PURPOSE

This article highlights the contributions of three pillars of an evidence-based practice approach (service providers, researchers, and families/clients) in the development of a framework to offer a way forward for professionals, families, and technology companies to support optimal visual and communication outcomes of individuals with cortical visual impairment (CVI) who use augmentative and alternative communication (AAC). By providing available research findings as well as practical information and lived experiences, the article offers clinical considerations and design features that can lead to addressing the unique needs of these individuals.

METHOD

This article reviews literature concerning what is known about CVI and describes in detail and from multiple viewpoints important features required in AAC systems to support individuals with CVI and enable them to communicate effectively.

RESULTS

Components necessary for teams, communication partners, and AAC designers to optimize AAC system design in CVI are presented using external research evidence as internal evidence from lived experience to support their importance.

CONCLUSIONS

An AAC system design that is tailored to the unique visual processing characteristics in CVI is likely to promote positive communication outcomes. The presentation of the lived experience of an individual who has CVI themselves illustrates the need for individualized assessments and interventions that incorporate and reflect the research presented here.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23902239.

Demands Associated With an Augmentative and Alternative Communication System in Relation to Alternative Forms of Access for Individuals With Motor Impairments

PURPOSE

Successful adoption and use of aided augmentative and alternative communication (AAC) must address how to promote fluid, efficient, and organized execution of the motor behavior needed to access the AAC system. A substantial number of people who use AAC have significant motor impairments and require "alternative" access options, such as eye gaze or switch use. Such individuals may be particularly vulnerable to interference from a poorly designed system. However, the inherent demands of alternative access methods have received little direct study. The goal of this tutorial is to offer a clinically and theoretically guided framework for considerations concerning AAC access, with the hope of spurring further discussion and empirical research.

METHOD

A framework that draws upon dynamic systems theory was used to illustrate the interactions between the various elements of importance to AAC access. Information and research from the fields of motor learning, developmental dynamic systems theory, AAC, and assistive technology was integrated into this tutorial to examine their applications for alternative AAC access methods.

RESULTS

The framework illustrated that AAC access involves a complex coordination between individual skills, the demands of the communication environment, the activity being undertaken, and the supports and demands inherent in the AAC system itself.

CONCLUSIONS

Awareness of the many demands that alternative forms of access place on the person who uses them can guide clinicians during assessment and intervention decision making regarding access options for individuals with significant motor impairments. Specific directions for future research are considered.

Examining the Visual Attention Patterns and Identification Accuracy of Adults With Aphasia for Grids and Visual Scene Displays

PURPOSE

We compared the degree of cognitive processing needed by people with aphasia to identify themes depicted in grids and visual scene displays (VSDs). We also compared the accuracy of theme identification for both display types.

METHOD

Eye-tracking technology was employed to measure the visual processing patterns of 21 adults with aphasia when interpreting themes presented through grids and VSDs. Additionally, we assessed theme identification accuracy by having participants select themes from four choices after viewing each display.

RESULTS

Participants more rapidly identified VSDs than grid displays, and VSDs required fewer visual fixations to process than grids. No significant differences were noted between grids and VSDs for theme identification accuracy; however, results indicate a ceiling effect for the variable, as participant accuracy levels were nearly 100% for both display conditions.

CONCLUSIONS

Results from this study add to a growing body of evidence supporting the use of VSDs for adults with aphasia. Both display types were accurately identified; however, VSDs were processed more efficiently than grids indicating that both display types may prove effective for people with aphasia; however, VSDs may require less cognitive effort to effectively use than grid displays.

Preference and visual cognitive processing demands of alphabetic and QWERTY keyboards of individuals with and without brain injury

Following a severe brain injury (BI), some literate individuals who require augmentative and alternative communication (AAC) strategies to support communication may benefit from the use of onscreen keyboards to generate text. A range of layouts are available to these individuals within specialized communication software. However, a paucity of information is available to describe user preferences, user perceptions, as well as the visual-cognitive processing demands of such layouts. Such information is critical to guide clinical decision-making for keyboard selection and to provide patient-centered services. This study: (a) described the preferences and perceptions of two onscreen keyboard layouts (QWERTY and alphabetic) and (b) used eye-tracking analysis to investigate the visual-cognitive processing demands between these onscreen keyboards for individuals with and without BI. Results indicated participants in both groups held a strong preference for QWERTY keyboard interfaces and had extensive prior experience using the QWERTY keyboard layout on mobile devices. Eye-tracking analysis revealed less visual-cognitive processing demands using a QWERTY keyboard layout for both groups but were only statistically significant for those without BI. Results suggest that use of a keyboard layout that aligns with client preferences and prior experiences (i.e., the QWERTY keyboard for these participants) may lead to increased satisfaction with the communication experience and increased communication efficiency.

Judicious Arrangement of Symbols on a Simulated Augmentative and Alternative Communication Display Optimizes Visual Attention by Individuals With Down Syndrome

PURPOSE

Aided augmentative and alternative communication (AAC) displays are often designed as symmetrical row-column grids, with each square in the grid containing a symbol. To maximize vocabulary on displays, symbols are often placed close to one another, and background color cuing is used to signal/differentiate symbols across different grammatical categories. However, from a visual and developmental standpoint, these display features (close-set symbols and use of background color cues) may not be optimal. In particular, placing symbols quite close together may result in visual crowding, in which individual symbols cannot be distinguished due to the presence of many neighbors, or flankers. This research sought to examine the role of display arrangement and background color cuing on the efficiency of visual attention during search.

METHOD

Ten adolescents and adults with Down syndrome underwent a visual search task while a research-based eye tracking system recorded their patterns of visual attention. Participants searched for symbol targets on displays with varying levels of visual crowding and background color cuing.

RESULTS

Spatial arrangements that reduced visual crowding and that used the spatial organization to cue the grammatical category of symbols resulted in significantly fewer fixations to nonrelevant distracters during search and reduced the likelihood of fixations away from the target once it was located. Background color was helpful in reducing the latency to find the target.

DISCUSSION

Spatial cues may offer a powerful means to maximize the efficiency of search within AAC displays. Background color cuing may facilitate speed to locate targets in these older individuals. Implications for AAC design, as well as future avenues for maximizing (growing) vocabulary, are discussed.

Clinical and Research Perspectives on Visual Scene Displays

Purpose The purposes of this study were to measure the perceptions of speech-language pathologists (SLPs) and researchers regarding the design of visual scene displays (VSDs) and to investigate the perceived difficulties of SLPs in regard to the acquisition and programming of VSDs. Method We recruited 270 SLPs and nine researchers who focus on VSDs to complete an online survey. The SLP survey addressed both perception of VSD design and difficulties associated with implementing these images as communication supports in the clinical realm. The researcher group was surveyed solely regarding their opinions associated with VSD design. Results SLPs and researchers both ranked high-context VSDs as more effective at supporting communication than low-context VSDs. In addition, both groups ranked VSDs with task-engaged people as more effective at supporting communication than VSDs with camera-engaged people or no people. SLPs reported difficulties with acquiring high-quality VSDs from online sources as well as difficulties with maintenance and upkeep of VSDs. In addition, a large portion of SLPs reported challenges with representing complex concepts through VSDs. Conclusions Results from this study provide evidence of general agreement between SLPs and researchers regarding perception of VSD design. SLPs continue to report challenges with the acquisition and programming of VSDs. Further research is needed to develop evidence-based guidelines to support clinical endeavors in these areas.

Visual Attention to Cued Targets in Simulated Aided Augmentative and Alternative Communication Displays for Individuals With Intellectual and Developmental Disabilities

Purpose Many aided augmentative and alternative communication (AAC) systems require the use of an external display that is represented via a visual modality. It is critical to evaluate and understand visual-perceptual processing in individuals with disabilities who could benefit from AAC. One way to evaluate how individuals process visual materials is through research-based automated eye-tracking technologies that obtain a fine-grained stream of data concerning gaze paths of visual attention. Method The current study examined how individuals with autism spectrum disorder (n = 13), Down syndrome (n = 13), intellectual and developmental disabilities (n = 9), or typical development (n = 20) responded to a spoken prompt to find a thumbnail-sized navigation key within a complex AAC display, including a main visual scene display (VSD) and a navigation bar of four thumbnail-sized VSDs. Stimuli were presented on a monitor containing automated eye-tracking research technology that recorded patterns of visual attention. Results Participants across groups spent more time fixating on a target thumbnail VSD navigation image after the presentation of the spoken cue to look at the target, compared to before the presentation of the spoken cue; they also spent more time looking at the target thumbnail VSD than the other thumbnail-sized VSDs in the navigation bar after the cue. Discussion Participants were able to locate the target thumbnail VSDs, even within the context of a visually complex AAC display. Implications for the design of AAC displays and for assessment of comprehension are discussed.

The Relation between Physiological Parameters and Colour Modifications in Text Background and Overlay during Reading in Children with and without Dyslexia

Reading is one of the essential processes during the maturation of an individual. It is estimated that 5-10% of school-age children are affected by dyslexia, the reading disorder characterised by difficulties in the accuracy or fluency of word recognition. There are many studies which have reported that coloured overlays and background could improve the reading process, especially in children with reading disorders. As dyslexia has neurobiological origins, the aim of the present research was to understand the relationship between physiological parameters and colour modifications in the text and background during reading in children with and without dyslexia. We have measured differences in electroencephalography (EEG), heart rate variability (HRV), electrodermal activities (EDA) and eye movements of the 36 school-age (from 8 to 12 years old) children (18 with dyslexia and 18 of control group) during the reading task in 13 combinations of background and overlay colours. Our findings showed that the dyslexic children have longer reading duration, fixation count, fixation duration average, fixation duration total, and longer saccade count, saccade duration total, and saccade duration average while reading on white and coloured background/overlay. It was found that the turquoise background, turquoise overlay, and yellow background colours are beneficial for dyslexic readers, as they achieved the shortest time duration of the reading tasks when these colours were used. Additionally, dyslexic children have higher values of beta (15-40 Hz) and the broadband EEG (0.5-40 Hz) power while reading in one particular colour (purple), as well as increasing theta range power while reading with the purple overlay. We have observed no significant differences between HRV parameters on white colour, except for single colours (purple, turquoise overlay, and yellow overlay) where the control group showed higher values for mean HR, while dyslexic children scored higher with mean RR. Regarding EDA measure, we found systematically lower values in children with dyslexia in comparison to the control group. Based on the present results, we can conclude that both pastel and intense background/overlays are beneficial for reading of both groups and all sensor modalities could be used to better understand the neurophysiological origins in dyslexic children.

Speech-Language pathologists' decisions when designing an aided AAC display for a compilation case study of a beginning communicator

PURPOSE

The current study sought to identify decisions speech-language pathologists (SLPs) make and their rationale for those decisions when designing an AAC display for a hypothetical school-aged child who was a beginning communicator. Augmentative and alternative communication (AAC) displays support communicative interactions for children who are unable to use spoken language to meet their communication needs. Children who are at the early stages of learning language, often termed beginning or emerging communicators, may rely heavily on the AAC display to support comprehension and expression. Thus, it is important for speech-language pathologists (SLPs) to design a display that facilitates beginning communicators' communication development.

METHODS

This paper reports on the answers related to a specific case study presented in an online survey completed by 77 SLPs with experience in AAC.

RESULTS

Data illustrated design decisions driven by child-specific characteristics and informed by research regarding type of layout, representation, and the importance of various design features.

CONCLUSIONS

Suggestions for future research are provided, including identifying goals and communicative functions best supported by different types of displays, clinicians' challenges/successes growing a system with the child, and determining the importance of symbol arrangement and organisation in communicative tasks by AAC users.Implications for RehabilitationIdentification of current practices reported by speech-language pathologists given a case study to develop and implement future research.A gap between research and practice suggests the need for better dissemination and application of research supporting the inclusion of people engaged in the event depicted in a visual scene display.Foundations for future research to provide guidance regarding best design of and communication goals supported by visual scene displays and grid-based displays.

Eye Tracking Measures Reveal How Changes in the Design of Displays for Augmentative and Alternative Communication Influence Visual Search in Individuals With Down Syndrome or Autism Spectrum Disorder

Purpose This research note reports on how small changes to the organization of a simulated display for augmentative and alternative communication influence the visual search patterns of individuals with Down syndrome or autism, as measured through eye tracking technologies. Prior research had demonstrated that clustering symbols by their internal color facilitates search and reduces attention to distracters, in children with typical development. This research systematically replicated the procedures with individuals with Down syndrome or autism spectrum disorder. Method Participants engaged in a visual search task on a monitor with embedded automated eye tracking technology. Patterns of gaze during search were measured via this technology. Results Participants were significantly faster to fixate on the target and to select it with the mouse when the like-colored symbols were clustered together. In addition, participants were significantly less likely to fixate on distracters in the clustered condition. No group differences were found. Conclusions Small changes to the organization of the simulated augmentative and alternative communication display resulted in substantial differences in eye gaze and speed to find a target. Of greatest clinical import is the finding that clustering symbols reduced attention to distracters, given that individuals with disabilities may be prone to distraction.

Designing effective AAC displays for individuals with developmental or acquired disabilities: State of the science and future research directions

This paper reviews research on the impact of AAC display variables on visual attention and performance of children with developmental disabilities and adults with acquired conditions, and considers implications for designing effective visual scene displays (VSDs) or grids. When using VSDs with children with developmental disabilities or adults with acquired conditions, research supports the use of personalized photo VSDs that include familiar people engaged in meaningful activities, with navigation bars with thumbnail VSDs, located adjacent to the main VSD. Adults with acquired conditions seem to benefit from the inclusion of text boxes adjacent to the scene. Emerging evidence supports the use of motion to capture visual attention to VSDs (video VSDs) or to specific elements in VSDs. When using grid displays with children with developmental disabilities, research supports the use of spatial cues and clustering based on internal symbol colour to facilitate visual searching and selection. Background colour does not seem to facilitate searching for symbols on smaller displays, and may actually distract children from processing the meaningful components of symbols. Preliminary research suggests that the organization of onscreen keyboards and the number, types, and pairings of symbols in grids may impact performance of adults with acquired conditions. Directions for future research are discussed.

Innovations for Supporting Communication: Opportunities and Challenges for People with Complex Communication Needs

Individuals with complex communication needs have benefited greatly from technological innovations over the past two decades, as well as from social movements that have shifted focus from disability to functioning and participation in society. Three strands of technological innovation are reviewed in this paper: (1) innovations in the tools that have become available, specifically tablet technologies; (2) innovations in access methods (eye gaze technologies and brain-computer interfaces); and (3) innovations in output, specifically speech technologies. The opportunities these innovations offer are explored, as are some of the challenges that they imply, not only for individuals with complex communication needs, but also for families, professionals, and researchers.

Cognitive-perceptual load modulates hand selection in left-handers to a greater extent than in right-handers

Previous studies have proposed that selecting which hand to use for a reaching task appears to be modulated by a factor described as "task difficulty," defined by either the requirement for spatial precision or movement sequences. However, we previously reported that analysis of the movement costs associated with even simple movements plays a major role in hand selection. We further demonstrated, in right-handers, that cognitive-perceptual loading modulates hand selection by interfering with the analysis of such costs. It has been reported that left-handers tend to show less dominant hand bias in selecting which hand to use during reaching. We, therefore, hypothesized that hand selection would be less affected by cognitive-perceptual loading in left-handers than in right-handers. We employed a visual search task that presented different levels of difficulty (cognitive-perceptual load), as established in previous studies. Our findings indicate that left-handed participants tend to show greater modulation of hand selection by cognitive-perceptual loading than right-handers. Left-handers showed lower dominant hand reaction times than right-handers, and greater high-cost movements that reached to extremes of the contralateral workspace under the most difficult task conditions. We previously showed in this task that midline crossing has high-energy and time costs and that they occur more frequently under cognitively demanding conditions. The current study revealed that midline crossing was associated with the lowest reaction times, in both handedness groups. The fact that left-handers showed lower dominant hand reaction times, and a greater number of high-cost cross-midline reaches under the most cognitively demanding conditions suggests that these actions were erroneous.

Consistent Symbol Location Affects Motor Learning in Preschoolers Without Disabilities: Implications for Designing Augmentative and Alternative Communication Displays

PURPOSE

Designing augmentative and alternative communication (AAC) displays that minimize operational demands is an important aspect of AAC intervention. The current study compared the effect of 2 display designs on the speed of locating target words by preschoolers without disabilities.

METHOD

Across 5 sessions, participants in the consistent condition (n = 12) were asked to locate symbols on arrays that did not change, whereas participants in the variable condition (n = 12) utilized arrays where the symbols changed locations each session.

RESULTS

No difference in response time across conditions was noted during the 1st session; however, by the 5th session, participants in the consistent condition demonstrated significantly faster response times than participants in the variable condition.

CONCLUSIONS

The current study illustrated an advantage of consistent symbol location for preschoolers without disabilities. Clinical applications for incorporating consistent symbol location into AAC display design are discussed; however, replication with children who use AAC is critical.

Is Hand Selection Modulated by Cognitive-perceptual Load?

Previous studies proposed that selecting which hand to use for a reaching task appears to be modulated by a factor described as "task difficulty". However, what features of a task might contribute to greater or lesser "difficulty" in the context of hand selection decisions has yet to be determined. There has been evidence that biomechanical and kinematic factors such as movement smoothness and work can predict patterns of selection across the workspace, suggesting a role of predictive cost analysis in hand-selection. We hypothesize that this type of prediction for hand-selection should recruit substantial cognitive resources and thus should be influenced by cognitive-perceptual loading. We test this hypothesis by assessing the role of cognitive-perceptual loading on hand selection decisions, using a visual search task that presents different levels of difficulty (cognitive-perceptual load), as established in previous studies on overall response time and efficiency of visual search. Although the data are necessarily preliminary due to small sample size, our data suggested an influence of cognitive-perceptual load on hand selection, such that the dominant hand was selected more frequently as cognitive load increased. Interestingly, cognitive-perceptual loading also increased cross-midline reaches with both hands. Because crossing midline is more costly in terms of kinematic and kinetic factors, our findings suggest that cognitive processes are normally engaged to avoid costly actions, and that the choice not-to-cross midline requires cognitive resources.

Observing eye movements and the influence of cognition during a symbol search task: a comparison across three age groups

This study examined eye movements during a visual search task as well as cognitive abilities within three age groups. The aim was to explore scanning patterns across symbol grids and to better understand the impact of symbol location in AAC displays on speed and accuracy of symbol selection. For the study, 60 students were asked to locate a series of symbols on 16 cell grids. The EyeLink 1000 was used to measure eye movements, accuracy, and response time. Accuracy was high across all cells. Participants had faster response times, longer fixations, and more frequent fixations on symbols located in the middle of the grid. Group comparisons revealed significant differences for accuracy and reaction times. The Leiter-R was used to evaluate cognitive abilities. Sustained attention and cognitive flexibility scores predicted the participants' reaction time and accuracy in symbol selection. Findings suggest that symbol location within AAC devices and individuals' cognitive abilities influence the speed and accuracy of retrieving symbols.

The effect of human engagement depicted in contextual photographs on the visual attention patterns of adults with traumatic brain injury

Photographs are a frequently employed tool for the rehabilitation of adults with traumatic brain injury (TBI). Speech-language pathologists (SLPs) working with these individuals must select photos that are easily identifiable and meaningful to their clients. In this investigation, we examined the visual attention response to camera- (i.e., depicted human figure looking toward camera) and task-engaged (i.e., depicted human figure looking at and touching an object) contextual photographs for a group of adults with TBI and a group of adults without neurological conditions. Eye-tracking technology served to accurately and objectively measure visual fixations. Although differences were hypothesized given the cognitive deficits associated with TBI, study results revealed little difference in the visual fixation patterns of adults with and without TBI. Specifically, both groups of participants tended to fixate rapidly on the depicted human figure and fixate more on objects in which a human figure was task-engaged than when a human figure was camera-engaged. These results indicate that strategic placement of human figures in a contextual photograph may modify the way in which individuals with TBI visually attend to and interpret photographs. In addition, task-engagement appears to have a guiding effect on visual attention that may be of benefit to SLPs hoping to select more effective contextual photographs for their clients with TBI. Finally, the limited differences in visual attention patterns between individuals with TBI and their age and gender matched peers without neurological impairments indicates that these two groups find similar photograph regions to be worthy of visual fixation.

LEARNING OUTCOMES

Readers will gain knowledge regarding the photograph selection process for individuals with TBI. In addition, readers will be able to identify camera- and task-engaged photographs and to explain why task-engagement may be a beneficial component of contextual photographs.

A Comparison of the Visual Attention Patterns of People With Aphasia and Adults Without Neurological Conditions for Camera-Engaged and Task-Engaged Visual Scenes

PURPOSE

The purpose of the study was to compare the visual attention patterns of adults with aphasia and adults without neurological conditions when viewing visual scenes with 2 types of engagement.

METHOD

Eye-tracking technology was used to measure the visual attention patterns of 10 adults with aphasia and 10 adults without neurological conditions. Participants viewed camera-engaged (i.e., human figure facing camera) and task-engaged (i.e., human figure looking at and touching an object) visual scenes.

RESULTS

Participants with aphasia responded to engagement cues by focusing on objects of interest more for task-engaged scenes than camera-engaged scenes; however, the difference in their responses to these scenes were not as pronounced as those observed in adults without neurological conditions. In addition, people with aphasia spent more time looking at background areas of interest and less time looking at person areas of interest for camera-engaged scenes than did control participants.

CONCLUSIONS

Results indicate people with aphasia visually attend to scenes differently than adults without neurological conditions. As a consequence, augmentative and alternative communication (AAC) facilitators may have different visual attention behaviors than the people with aphasia for whom they are constructing or selecting visual scenes. Further examination of the visual attention of people with aphasia may help optimize visual scene selection.

Eye tracking research to answer questions about augmentative and alternative communication assessment and intervention

Recently, eye tracking technologies (i.e., technologies that automatically track the point of an individual's gaze while that person views or interacts with a visual image) have become available for research purposes. Based on the sampling of the orientation of the individual's eyes, researchers can quantify which locations within the visual image were fixated (viewed), for how long, and how many times. These automated eye tracking research technologies open up a wealth of avenues for investigating how individuals with developmental or acquired communication disabilities may respond to aided augmentative and alternative communication (AAC) systems. In this paper, we introduce basic terminology and explore some of the special challenges of conducting eye tracking research with populations with disabilities who might use AAC, including challenges of inferring attention from the presence of fixation and challenges related to calibration that may result from participant characteristics, behavioral idiosyncracies, and/or the number of calibration points. We also examine how the technology can be applied to ask well-structured experimental questions that have direct clinical relevance, with a focus on the unique contributions that eye tracking research can provide by (a) allowing evaluation of skills in individuals who are difficult to assess via traditional methods, and (b) facilitating access to information on underlying visual cognitive processes that is not accessible via traditional behavioral measures.