Research Interests

Spatial navigation is an essential task, without which finding the bathroom from the bedroom becomes a challenge. Our ability to navigate in the world relies upon attending to the appropriate information as it enters our senses. Typically, spatial navigation behavior is supported by visual navigation cues – signs, verbal instructions, and maps – that show the way to go. Thus, before these cues can be useful, people need to find and attend to them, a task requiring two distinct aspects of attention: re-orienting toward an object (object-based attention) and re-orienting to a location in space (space-based attention). This line of research (1) investigates the relation between object- and space-based attentional re-orienting mechanisms and measures of spatial navigation; and (2) how visual attention is modulated by different representational formats of spatial direction, such as arrows, words, and scenes. Some of my preliminary findings reveal that spatial attention is captured more efficiently by arrows and words, which suggests that these formats may be more effective supports than scenes for navigation performance.

With a growing aging population and the prevalence of Alzheimer’s disease expected to more than double in the next few decades, improving diagnostic procedures to help with early detection and accurate diagnosis of Alzheimer’s disease is crucial. It is known that Alzheimer’s disease patients exhibit impairments in attentional re-orienting, showing general deficits in both object- and space-based attentional re-orienting. Critically, the presence of attentional re-orienting impairments in Alzheimer’s disease patients presents an opportunity to examine whether similar deficits are evident in persons who are at risk of cognitive decline. Indeed, research indicates that persons with Mild Cognitive Impairment, which is a prodromal phase of Alzheimer’s disease, are also impaired at re-orienting space-based attention as compared to healthy age-matched controls, but it is unknown whether this deficit generalizes to object-based attentional re-orienting and what changes to the neural pathway/s cause this deficit. A better understanding of visual attention in the early stages of Alzheimer’s disease is critical to developing and refining the novel diagnostic capabilities of this cognitive process. Thus, the goals of this line of research are to (1) determine the extent to which patients with Mild Cognitive Impairment have a deficit in object- and/or space-based attentional re-orienting; (2) examine the functional and structural connectivity between attentional neural network nodes supporting object- and space-based attentional re-orienting in patients with Mild Cognitive Impairment and healthy controls; and (3) determine whether attentional re-orienting deficits are predictive of spatial navigation deficits, which are common in normal aging and are exacerbated in Alzheimer’s disease patients.

My graduate research contributions focused on the mechanisms of re-orienting object-based attention. Results from a novel behavioral paradigm revealed a consistent finding – re-orienting object-based attentional resources across the visual field meridians, or midlines of the screen, resulted in a consistent advantage for targets located horizontally as compared to vertically from a cued location. This unequal re-orienting of object-based attention is termed the “Shift Direction Anisotropy” or SDA. This effect was observed regardless of whether re-orienting object-based attention occurred within a single cued object, or between cued and non-cued objects, suggesting a critical modulatory role of the visual field meridians on the re-orienting of object-based attentional selection. Additionally, I found that the SDA is driven by target location, rather than object placement, relative to the meridians, suggesting that object-based attention processes prioritize specific target locations within an object. Together, this work provides a new theoretical understanding of object-based attention to account for the visual field meridians and provides the foundation for investigations into the effects of the meridians on real-world object-based attention.

The discovery of the Shift Direction Anisotropy (SDA) in my early work set the stage for further characterization and understanding of this novel object-based effect. First, I investigated whether manipulating the perceptual visibility and local feature contrast of the meridians impacted the SDA. Strong manipulations (i.e., a white line) of the horizontal meridian eliminated the SDA, whereas weaker manipulations and manipulations of the vertical meridian had no effect, indicating that an enhanced horizontal meridian serves to sequester attentional resources, reducing competition between targets on either side of the horizontal meridian. Second, I investigated whether the SDA was driven by the local judgement of targets (e.g., a horizontal local judgement for ‘E’ and ‘3’ versus a vertical local judgement for ‘T’ and ‘L’). Consistent SDAs were observed for both types of target local judgements, indicating that the directional judgement of the targets did not affect the SDA. Finally, I tested whether the SDA is a better measure of object-based re-orienting than the traditional effect, called the “same object advantage”. Mounting evidence suggests that the same object advantage is inconsistent, small in magnitude, and observed in a minority of participants, which ultimately encourages questions regarding the legitimacy of object-based re-orienting. I found larger and more prevalent effects for the SDA versus the same-object advantage within subjects, suggesting that the SDA is a more stable and reliable measure of object-based re-orienting that the same-object advantage. The collective findings of this work reveal important properties of the SDA.  

During my first postdoctoral position, I explored whether the selection of objects underlies failures of awareness (i.e., change blindness) and investigated whether some people are more susceptible to failures of awareness. The goal of these studies was to clarify whether failures of awareness are random or stable individual characteristics, as well as to identify factors that can be used to predict failures of awareness. For example, I found that participants’ metacognitive ratings of change detection ability predicted their change blindness duration (as well as change blindness in others), such that changes rated as likely to be spotted were detected faster than changes rated as unlikely to be spotted. Moreover, such metacognitive judgements explained unique variance in change blindness, above and beyond both low-level and semantic image properties. Together, these findings reveal that people can accurately rate the relative difficulty of different changes and predict change blindness for different images and that metacognitive judgements of change detection likelihood are not fully explained by low-level and semantic image properties.