Summary: Two primary Signal Detection Theory metrics—perceptual certainty and response bias—track with changes in cognitive fatigue.
Source: Kessler Foundation
Researchers in New Jersey report that two central measures from Signal Detection Theory (SDT)—perceptual certainty and response bias—change in parallel with fluctuations in cognitive fatigue. They also show that these SDT measures vary with brain activation patterns measured by functional MRI.
The study appeared in Frontiers in Psychology on January 15, 2021.
Authors: Glenn Wylie, DPhil; Brian Yao, PhD; John DeLuca, PhD (Kessler Foundation); and Joshua Sandry, PhD (Montclair State University).
Cognitive fatigue is a common, often persistent feeling of mental tiredness that affects healthy people as well as those with brain injury or neurodegenerative disease. A longstanding puzzle in fatigue research is the mismatch between subjective fatigue and objective performance: people can feel fatigued while measurable accuracy or reaction times remain largely unchanged. That gap has left researchers without a reliable behavioral measure that consistently covaries with the subjective experience of cognitive fatigue.
Previous work suggested that one SDT metric, perceptual certainty (d’), might change with fatigue. However, it was unclear whether perceptual certainty reliably covaries with fatigue levels. Even less was known about the other key SDT metric, response bias (also called criterion)—the internal threshold a person uses to decide whether sensory evidence is sufficient to respond. Understanding how both SDT metrics relate to subjective fatigue is important for developing objective measures and, ultimately, better interventions.
The research took place at the Rocco Ortenzio Neuroimaging Center at Kessler Foundation, a facility dedicated to rehabilitation research. The team induced cognitive fatigue in 39 healthy volunteers by having them perform repeated runs of an n-back working memory task while structural and functional MRI data were collected.
Participants rated their momentary cognitive fatigue using a visual analogue scale (VAS-F) at baseline and after each of eight task runs. This design allowed the investigators to examine whether moment-to-moment changes in perceptual certainty and response bias tracked self-reported fatigue, and whether similar brain regions underpinned both subjective fatigue and SDT-derived measures.
Results showed that both SDT measures were sensitive to changes in cognitive fatigue. As participants reported greater fatigue, their perceptual certainty (d’) declined and their response bias shifted toward a more conservative criterion—meaning they required stronger evidence before making a positive response. This study is the first to demonstrate a direct correlation between fluctuations in cognitive fatigue and changes in perceptual certainty.
Neuroimaging results connected these behavioral changes to activation in the striatum, a part of the basal ganglia. The striatum had previously been identified by Kessler investigators as responsive to cognitive fatigue; here, its activation also related to both response bias and perceptual certainty, linking subjective experience, behavior, and brain function.
“Our findings show that cognitive fatigue is associated with systematic shifts in response bias and declines in perceptual certainty,” said lead author Dr. Glenn Wylie, director of the Ortenzio Center. “We propose that as people grow fatigued, perceptual sensitivity drops and they compensate by adopting a more conservative response strategy, which helps explain some error patterns seen during fatigue.”
The authors emphasize that SDT measures offer a promising, objective behavioral tool to study cognitive fatigue. By combining these measures with neuroimaging, researchers can better distinguish which neural systems drive subjective fatigue versus those that reflect task-related decision processes.
Funding: New Jersey Commission for Brain Injury Research (10.005.BIR1) and the National Multiple Sclerosis Society (RG 4232A1/1)
About this neuroscience research news
Source: Kessler Foundation
Contact: Carolann Murphy – Kessler Foundation
Image: The image is in the public domain
Original Research: Open access.
“Using Signal Detection Theory to Better Understand Cognitive Fatigue” by Glenn Wylie, DPhil; Brian Yao, PhD; John DeLuca, PhD; and Joshua Sandry, PhD. Frontiers in Psychology
Abstract
Using Signal Detection Theory to Better Understand Cognitive Fatigue
People often report that their performance feels worse when they are mentally fatigued, yet for decades objective measures (accuracy, reaction time) have not consistently matched those subjective reports. Signal Detection Theory offers two complementary metrics—response bias (criterion) and perceptual certainty (d’)—that describe decision thresholds and sensitivity. Prior studies hinted that these metrics might change with fatigue, but few have examined whether they covary with fatigue in the moment.
In this study, fatigue was induced via repeated n-back working memory tasks while participants underwent fMRI scanning. Cognitive fatigue ratings were collected at intervals, allowing analysis of whether criterion and d’ shifted alongside self-reported fatigue, and whether similar brain activation patterns supported both subjective fatigue and SDT measures.
The findings show that as cognitive fatigue increased, participants adopted a more conservative response bias and experienced a decline in perceptual certainty (d’). Activity in the striatum of the basal ganglia correlated with cognitive fatigue as well as with both SDT measures. These results indicate that SDT metrics can serve as objective behavioral markers of cognitive fatigue, and that while they overlap with fatigue-related brain activity, they also reflect distinct aspects of decision processing.
Overall, this work highlights the value of applying Signal Detection Theory to the study of fatigue and provides researchers with measurable behavioral and neural targets to advance understanding and treatment of cognitive fatigue.