Research Interests

My research interests are closely aligned with the goals of psychology and cognitive science - to understand the nature of the human mind. This truly is an ultimate scientific question, with numerous facets and many unresolved issues and challenges. I am intrinsically interested in the details of psychological phenomena, which fuels my passion for basic research to create and validate theories to explain them. At the same time, I am drawn to research that is relevant outside the laboratory, where results can help in understanding and addressing important societal issues. My approach emphasizes developing and validating quantitative theoretical mechanisms to account for the capacities and limitations of human cognition in greater breadth and depth. In pursuing these interests, I focus on integrative theories that span components of cognition, and levels of explanation. Finally, I test and apply my theories in complex, naturalistic tasks to demonstrate the relevance in real-world contexts.

For the last 10 years, my primary research area has been investigating the impact of fatigue and related factors on cognitive processing. The overwhelming majority of models developed and validated in psychology and cognitive science embody an implicit assumption that the cognitive system is operating efficiently and effectively in pursuing task goals. This assumption is tenuous in laboratory contexts, and there are numerous factors that routinely modulate cognitive performance outside the laboratory. This gap between scientific understanding and societal needs is not a recent phenomenon. However, technological innovations have created new challenges that reinforce and amplify the need to mitigate risks associated with fatigue and other factors across industries to improve safety. To be successful, applied psychological research must be supported by scientific advances in human factors and cognitive science.

My research on fatigue has focused on developing and validating mechanisms that provide detailed accounts of changes in performance associated with sleep loss, circadian rhythms, and time on task. I have proposed a mechanism that impacts central cognitive functioning by introducing brief interruptions, called microlapses, in goal-directed cognitive processing that increase in probability with greater fatigue. This mechanism leads to performance decrements that closely match the behavior of people performing a sustained attention task while sleep deprived, including the impact of time on task at different levels of sleep deprivation and individual differences in performance degradation. Importantly, the mechanisms are situated within the existing theoretical literature on sleep, providing a quantitative instantiation of the state instability hypothesis that is able to account for both increased response times and performance lapses.

Critically, the theoretical account extends beyond sustained attention. For instance, the current account makes predictions about strategy choice and learning. Additionally, I have proposed extensions to the theory that capture the effects of sleep loss in domains like declarative knowledge access, learning, and time perception. More research is needed to validate these mechanisms fully, and there remain questions about the impact of fatigue on other components of cognition, including visual perception and motor action. These are important theoretical questions to address, because the precise consequences of fatigue in real-world situations emerge from the integrated functioning of a set of cognitive components.

Beyond the theoretical implications of the research, I am motivated by the pressing needs for technologies to mitigate the consequences of fatigue in the real world - in the medical field, in aviation and transportation more generally, in military operations, and in countless other domains where the 24/7 nature of modern society conflicts with intrinsic dynamics of human alertness. Because of this, an important aspect of this research has been focused on assessing the extent to which the mechanisms can be generalized to account for performance changes in more naturalistic task contexts. In fact, I have been able to demonstrate that the theoretical account can be used to make meaningful predictions about the impact of fatigue in domains as complex as driving and remotely piloting aircraft.

Recently, the same mechanism has been applied to provide an account of performance changes associated with the vigilance decrement. This research is the first to establish a common theoretical mechanism spanning these two domains that, surprisingly, have developed theoretical accounts largely in parallel for decades. To validate the theory in greater detail, I am currently using electroencephalography (EEG) to associate computational mechanisms with changes in the magnitude and timing event-related potentials associated with the vigilance decrement. As with sleep deprivation, the mechanisms are consistent with recent theories of the vigilance decrement. Specifically, a recent account referred to as resource-control suggests that vigilance tasks place pressure on executive control resources. As they are depleted, maintenance of attentional focus becomes more difficult, leading to mind-wandering behavior. The resource-control theory and the mechanisms I have proposed provide a synthesis between the two primary theories in this domain. Microlapses implement a form of mind-wandering, brought on by breakdowns in attentional control caused by decrements to parameters (i.e., resources) associated with selecting and executing goal-directed cognitive actions.

Bringing unification to these domains is a valuable theoretical contribution to the literature. At the same time, it has the potential to further benefit applied research targeted at reducing the risks associated with the combined effects of fatigue and vigilance in environments where long hours are coupled with responsibilities that involve monitoring and supervisory control. As automation and autonomous systems proliferate in modern society, these kinds of jobs are becoming increasingly common, and the risks associated with lapses of attention and fatigue-related errors are becoming more significant. New approaches to fatigue risk management are needed ensure the safety of these operations.

There are many other factors beyond fatigue and vigilance that routinely impact cognitive processing. I refer to this broader class of factors as cognitive modulators. Like fatigue, they are ubiquitous in contemporary society and influence cognition and behavior both within and outside the laboratory. These include things like ingested chemicals (e.g., caffeine and zolpidem), environmental factors (e.g., oxygen levels and atmospheric pollutants), and other influences (e.g., workload, stress, and emotions). In collaboration with colleagues at the Air Force Research Laboratory, I have begun exploring extensions of my methodology to workload and physiological influences on cognitive performance. As in my research on fatigue, this research involves linking models of physiological and neurofunctional processes to parameters and mechanisms in a cognitive architecture that impact the efficiency and effectiveness of cognitive processing. In all cases, I emphasize carefully controlled empirical research combined with computational process modeling. This leads to detailed theoretical mechanisms, validated using human performance data, which advance basic science while facilitating the application of scientific ideas and insights to address real world challenges.

Unifying Themes

My research interests share several important characteristics. First, I have emphasized topics where there is potential for basic research insights to transition to real-world contexts and produce significant benefits. In addition, I am committed to developing computational mechanisms to instantiate theoretical claims. Finally, I am drawn to research areas that offer exciting opportunities to bridge across different methodologies and levels of analysis to develop more detailed and comprehensive theories that inform our understanding of the human mind.

I refer to my overall approach as multiscale modeling - combining models cast at different levels of abstraction to provide a more complete and comprehensive account of cognitive and behavioral phenomena. It represents an attempt to build bridges between physiology, neurofunctioning, and changes in cognitive processing to understand how cognitive modulators impact the efficiency and effectiveness of cognitive processing. There are extensive applications of this research across industries where modulated cognition increases the risks to operational outcomes as well as operator safety. As my scientific career continues, I will emphasize conducting carefully-controlled empirical studies to expose relevant phenomena, while also developing and validating computational mechanisms to explain the results and generate novel predictions that can be transitioned outside the laboratory.

Publications available online here.