What do fast response times tell us about attentional control?

The Stroop interference effect—slower responses to the color of an incongruent color-word stimulus (e.g., GREEN in red ink) compared to a neutral stimulus (e.g., XXXX in red ink)—is one of the most robust findings in cognitive psychology. This thesis investigated why the effect is so robust, focusing on the unique perceptual architecture of the Stroop stimulus. Specifically, in a Stroop stimulus, the visual word form and color are integrated into a visual object, and hence attending to the color inevitably results in the word receiving attention as well. Across four empirical chapters, I demonstrated that presenting the distractor word in advance of a Stroop stimulus (a manipulation termed <i>distractor priming</i>—e.g., presenting the word GREEN in white ink followed by the same word GREEN in red ink) significantly reduced—and in some cases eliminated—the Stroop interference effect. I argued that this occurred because the distractor prime broke the integration of the visual word form and color in the Stroop stimulus, allowing rapid disengagement of attention from the word. Crucially, I examined response time (RT) distributions. In standard Stroop stimuli, the interference effect increased with slower responses, yielding a positively sloped delta plot. When the integration was disrupted by distractor priming, the delta slope flattened—that is, the interference effect remained constant across the RT distribution. Chapter 2 introduced the distractor priming paradigm. Consistent with prior studies of distractor priming that used oral color-naming responses, distractor priming in a manual Stroop task sped up responses to the color. Importantly, it eliminated the Stroop interference effect across the entire RT distribution (i.e., it removed the positively sloped delta). Chapter 3 demonstrated that this reduction in Stroop interference and removal of the positively sloped delta occurred only with a prime visually identical to the distractor. Stroop interference remained large, and the positively sloped delta persisted when the prime was conceptually related but not visually identical to the distractor word (e.g., LEAF - GREENred) or an auditory word (e.g., hearing “green”). Chapter 4 explored the relative “automaticity” of the distractor priming benefit and demonstrated that even when the word precue was only 50% predictive of the upcoming distractor word (unlike 100% as in the previous studies), Stroop interference was reduced and the positively sloped delta removed. Additionally, this experiment showed that the delta slope pattern of the Stroop interference effect found in the distractor-primed (identity precue) condition differed from that in the response-precue condition (e.g., the word RED followed by the word GREEN in red ink). Chapter 5 tested the assumption underlying the distractor priming benefit—that the positively sloped delta was removed when the integration between the word and color was disrupted—using the primed Stroop task. This paradigm differed from the standard Stroop task in that the word and color were not integrated into a single visual object; instead, the distractor word was presented ahead of a row of colored Xs. Across two experiments, RT distributions in the primed Stroop task mirrored those in distractor priming, in that Stroop interference was small and the positively sloped delta was eliminated. Together, these findings indicate that the robustness of the Stroop interference effect stems from the perceptual integration of the distractor word and color into a single visual object. Chapter 6 provides a discussion of the implication of our interpretation of Stroop interference on how the Stroop task is used as a tool to study selective attention.

Although response times (RTs) are the dependent measure of choice in the majority of studies of visual attention, changes in RTs can be hard to interpret. First, they are inherently ambiguous, since they may reflect a change in the central tendency or skew (or both) of a distribution. Second, RT measures may lack sensitivity, since meaningful changes in RT patterns may not be picked up if they reflect two or more processes having opposing influences on mean RTs. Here we describe RT distributions for repetition priming in visual search, fitting ex-Gaussian functions to RT distributions. We focus here on feature and conjunction search tasks, since priming effects in these tasks are often thought to reflect similar mechanisms. As expected, both tasks resulted in strong priming effects when target and distractor identities repeated, but a large difference between feature and conjunction search was also seen, in that the σ parameter (reflecting the standard deviation of the Gaussian component) was far more affected by search repetition in conjunction than in feature search. Although caution should clearly be used when particular parameter estimates are matched to specific functions or processes, our results suggest that analyses of RT distributions can inform theoretical accounts of priming in visual search tasks, in this case showing quite different repetition effects for the two differing search types, suggesting that priming in the two paradigms partly reflects different mechanisms.

Response time is more important than walking speed for the ability of older adults to avoid a fall after a trip

In response time (RT) research, RT outliers are typically excluded from statistical analysis to improve the signal-to-noise ratio. Nevertheless, there exist several methods for outlier exclusion. This poses the question, how these methods differ with respect to recovering the uncontaminated RT distribution. In the present simulation study, two RT distributions with a given population difference were simulated in each iteration. RTs were replaced by outliers following two different approaches. The first approach generated outliers at the tails of the distribution, the second one inserted outliers overlapping with the genuine RT distribution. We applied ten different outlier exclusion methods and tested, how many pairs of distributions significantly differed. Outlier exclusion methods were compared in terms of bias. Bias was defined as the deviation of the proportion of significant differences after outlier exclusion from the proportion of significant differences in the uncontaminated samples (before introducing outliers). Our results showed large differences in bias between the exclusion methods. Some methods showed a high rate of Type-I errors and should therefore clearly not be used. Overall, our results showed that applying an exclusion method based on z-scores / standard deviations introduced only small biases, while the absence of outlier exclusion showed the largest absolute bias.

The purpose of this study was to describe objective sleep-wake characteristics and glycemia over 7-14 days in young adults with type 1 diabetes. In addition, person-level associations among objective sleep-wake characteristics (total sleep time, sleep variability, and sleep fragmentation index), daytime sleepiness, and glycemia (glycemic control and glucose variability) were examined. In this cross-sectional study, objective sleep-wake characteristics were measured via actigraphy and glucose variability via continuous glucose monitoring over 6-14 days. At baseline, participants completed the Psychomotor Vigilance Test, the Trail Making Test, and questionnaires on daytime sleepiness, sleep quality, and sleep disturbance including sleep diaries. Forty-six participants (mean age, 22.3 ± 3.2 years) wore a wrist actigraph and underwent continuous glucose monitoring concurrently for 6-14 days. Greater sleep variability was directly associated with greater glucose variability (mean of daily differences; r = .33, P = .036). Higher daytime sleepiness was directly associated with greater glucose variability (mean of daily differences; r = .50, P = .001). The association between sleep variability and glucose variability (mean of daily differences) was no longer significant when accounting for daytime sleepiness and controlling for type 1 diabetes duration (P > .05). A higher sleep fragmentation index was associated with greater glucose variability (B = 1.27, P = .010, pr2 = 0.40) after controlling for type 1 diabetes duration and accounting for higher daytime sleepiness. Sleep-wake variability, sleep fragmentation, daytime sleepiness, and the associations with glycemia are new dimensions to consider in young adults with type 1 diabetes. Sleep habits in this population may explain higher glucose variability, and optimizing sleep may improve overall diabetes management. Griggs S, Hickman RL Jr, Strohl KP, Redeker NS, Crawford SL, Grey M. Sleep-wake characteristics, daytime sleepiness, and glycemia in young adults with type 1 diabetes. J Clin Sleep Med. 2021;17(9):1865-1874.

Previous analyses of response time distributions have shown that the Stroop effect is observed in the mode (μ) and standard deviation (σ) of the normal part of the distribution, as well as its tail (τ). Specifically, interference related to semantic and response processes has been suggested to specifically affect the mode and tail, respectively. However, only one study in the literature has directly manipulated semantic interference, and none manipulating response interference. The present research aims to address this gap by manipulating both semantic and response interference in a manual response Stroop task, and examining how these components of Stroop interference affect the response time distribution. Ex-Gaussian analysis showed both semantic and response conflict to only affect τ. Analyzing the distribution by rank-ordered response times (Vincentizing) showed converging results as the magnitude of both semantic and response conflict increased with slower response times. Additionally, response conflict appeared earlier on the distribution compared to semantic conflict. These findings further highlight the difficulty in attributing specific psychological processes to different parameters (i.e., μ, σ, and τ). The effect of different response modalities on the makeup of Stroop interference is also discussed.

In this work, a preliminary conceptual model of the hydrogeological functioning of a binary karst aquifer located in southern Spain is presented, based on the natural responses of the springs and the dye tracer tests. Results derived from the long-term analysis of cross-correlation function (CCF) (global average time of recharge input) have been validated with those obtained from a dye tracer test, performed during a specific recharge event. The overall response times (CCF results) obtained for the three springs studied were 58 (SP-1), 72 (SP-3), and 81 h (SP-2). This pattern in response times was contrasted with the first detection times of the BTC-Tracer Breakthrough Curve—at the same three springs (30.9, 35.3, and 47 h) and their respective recovery rates (2.03, 21.9, and 78.4% for S1, S2, and S3, respectively). The distribution of response times, both those determined by long-term statistical analysis and the ones derived from the use of dye tracer test, is directly related to the karst network development in each of the drainage routes. Additionally, the rate of tracer recovery at each of the springs is linked to the hierarchy of flow paths from the selected injection point toward each spring, within the overall drainage network scheme. An accurate knowledge of all factors affecting the hydrogeological behavior as well as groundwater flow paths (from swallow holes to the springs) is crucial for suitable management of the resource and to mitigate the pollution risks derived from fast infiltration of surface water.KeywordsCross-correlationDye tracer testKarst aquiferTime lagAquifer functioning

In a Fork-Join (FJ) queueing system an upstream fork station splits incoming jobs into N tasks to be further processed by N parallel servers, each with its own queue; the response time of one job is determined, at a downstream join station, by the maximum of the corresponding tasks' response times. This queueing system is useful to the modelling of multi-service systems subject to synchronization constraints, such as MapReduce clusters or multipath routing. Despite their apparent simplicity, FJ systems are hard to analyze. This paper provides the first computable stochastic bounds on the waiting and response time distributions in FJ systems. We consider four practical scenarios by combining 1a) renewal and 1b) non-renewal arrivals, and 2a) non-blocking and 2b) blocking servers. In the case of non blocking servers we prove that delays scale as O(logN), a law which is known for first moments under renewal input only. In the case of blocking servers, we prove that the same factor of log N dictates the stability region of the system. Simulation results indicate that our bounds are tight, especially at high utilizations, in all four scenarios. A remarkable insight gained from our results is that, at moderate to high utilizations, multipath routing 'makes sense' from a queueing perspective for two paths only, i.e., response times drop the most when N = 2; the technical explanation is that the resequencing (delay) price starts to quickly dominate the tempting gain due to multipath transmissions.

The current study examined the effects of responses on error-adjacent trials (i.e., those immediately preceding or following errors) on age differences in measures of intraindividual variability and the shape of response time (RT) distributions on a two-back task. Removing error-adjacent responses reduced variability as measured by the coefficient of variation, but did so similarly for younger and older adults. However, older adults’ standard deviations (SDs) were less than those of younger adults with comparable RTs, raising questions regarding the validity of the coefficient of variation. An ex-Gaussian analysis revealed that removing the RTs on error-adjacent trials reduced the length of the tails of distributions and the skewness of the distributions. These properties were reduced more for older adults than for younger adults. These results indicate that the influence of error-adjacent trials should be considered when analyzing intraindividual variability and the shape of RT distributions to test theories of cognitive aging.

Mechanisms by which the brain monitors and modulates performance are an important focus of recent research. The conflict-monitoring hypothesis posits that the ACC detects conflict between competing response pathways which, in turn, signals for enhanced control. The N2, an ERP component that has been localized to ACC, has been observed after high conflict stimuli. As a candidate index of the conflict signal, the N2 would be expected to be sensitive to the degree of response conflict present, a factor that depends on both the features of external stimuli and the internal control state. In the present study, we sought to explore the relationship between N2 amplitude and these variables through use of a modified Eriksen flankers task in which target-distracter compatibility was parametrically varied. We hypothesized that greater target-distracter incompatibility would result in higher levels of response conflict, as indexed by both behavior and the N2 component. Consistent with this prediction, there were parametric degradations in behavioral performance and increases in N2 amplitudes with increasing incompatibility. Further, increasingly incompatible stimuli led to the predicted parametric increases in control on subsequent incompatible trials as evidenced by enhanced performance and reduced N2 amplitudes. These findings suggest that the N2 component and associated behavioral performance are finely sensitive to the degree of response conflict present and to the control adjustments that result from modulations in conflict.

We consider the synchronization problem for ho- mogeneous networks of nonlinear SISO agents connected via dif- fusive partial-state coupling. The agents are non-introspective (i.e., they do not have access to their own state or output), and thus unable to manipulate their own dynamics in order to present themselves differently to the network. Moreover, the agents are not allowed to exchange additional information, such as internal controller states, over the network. Unlike many other designs for nonlinear synchronization, we do not require the agents to be passive; we rely instead on a canonical form that requires the nonlinearities to have a certain lower- triangular structure.

This thesis presents a comprehensive study of tailored semiconductor devices that bridge conventional photodetection with neuromorphic photomemory applications through strategic engineering of response time characteristics. The fundamental insight underlying this work is that response time represents the critical parameter determining whether an optoelectronic device functions as a conventional photodetector or enables synaptic functionality for brain-inspired computing systems. The research demonstrates that the same physical mechanisms, such as photon absorption, carrier generation, charge transport, and recombination, can be optimized for dramatically different temporal characteristics, enabling devices that adapt their functionality based on operational requirements. Fast response times in the microsecond to millisecond range enable high-speed photodetection for telecommunications and sensing applications, while prolonged response times through persistent photoconductivity (PPC) spanning seconds to days enable the memory and learning functions essential for artificial synapses. The research contributions are organized into four interconnected studies that collectively demonstrate this dual functionality principle. Chapters 2 and 3 focus on optimizing devices for fast photodetection applications. Chapter 2 presents flexible germanium/titanium nitride (Ge/TiN) photodetectors that achieve enhanced near infrared responsivity through plasmonic enhancement and strain engineering, demonstrating how structural modifications can improve conventional photodetection performance while maintaining fast response characteristics. Chapter 3 investigates self powered silicon metal-semiconductor-metal (MSM) photodetectors utilizing asymmetric electrode configurations, achieving efficient photodetection without external bias through engineered Schottky barrier heights. Chapters 4 and 5 shift focus on exploiting extended response times for neuromorphic applications. Chapter 4 demonstrates silicon/indium gallium zinc oxide (Si/IGZO) photomemory devices with persistent photoconductivity exceeding nine days, achieved through substrate conductivity engineering that optimizes band alignment to trap photocarriers and prevent recombination. Chapter 5 presents transparent quartz/IGZO tracking devices that combine optical transparency with neuromorphic functionality, enabling covert trajectory monitoring through synaptic plasticity behaviors. The connection between these studies lies in the systematic exploration of how response time engineering enables the same semiconductor materials to serve two different purposes. The Ge/TiN and Si photodetectors in Chapters 2-3 are optimized for response times in the millisecond range, suitable for high-speed optical communication and imaging applications. In contrast, the IGZO-based devices in Chapters 4-5 exploit response times spanning minutes to days, enabling synaptic behaviors including PPF, learning-forgetting-relearning cycles, and long-term memory retention. All four device systems are based on MSM-type architectures that share the same fundamental band-to band excitation and carrier transport principles, and flexibility, self-powered operation, photomemory, and trajectory tracking are employed as representative manifestations of fast and slow response-time engineering within this common framework. The research provides new insights into the mechanisms controlling persistent photoconductivity, demonstrates practical strategies for substrate and interface engineering, and establishes design principles for next-generation neuromorphic optoelectronic systems. The significance of this research extends beyond individual device performance improvements to establish a fundamental framework for engineering semiconductor devices with tunable temporal characteristics. By demonstrating that the same materials and fabrication processes can yield devices optimized for either fast photodetection or extended photomemory functions, this work opens new possibilities for semiconductor devices with tunable temporal characteristics and design-level flexibility in their functional role.

Timely delivery of emergency services is a critical priority in healthcare systems worldwide, with both speed and accuracy in patient care serving as essential indicators of service quality. This study investigates the relationship between nurses’ response time and patient satisfaction in the emergency department of Ibnu Sina Islamic Hospital, Pekanbaru. A quantitative, cross-sectional design was employed from December 2023 to July 2024. The study population consisted of family members accompanying patients to the emergency department. Using accidental sampling and the Slovin formula, a total of 94 participants were selected. Data were analyzed using the Chi-Square statistical test. Among the respondents, 83 individuals (88.3%) rated the response time as fast, while 11 (11.7%) perceived it as slow. In terms of satisfaction, 72 respondents (76.6%) reported being satisfied, whereas 22 (23.4%) expressed dissatisfaction. Chi-Square analysis revealed a statistically significant association between response time and patient satisfaction (p = 0.003, p &lt; 0.05), indicating that faster response times are positively correlated with higher levels of patient satisfaction in the emergency department. Keywords: Nurse, Response Time, Patient Satisfaction, Emergency Department, Hospital.

Highly sensitive flexible pressure sensor based on ionic dielectric layer with hierarchical ridge microstructure

A transaction scheduling mechanism is designed for a shared memory, multiprocessor database system. The scheduler used is a variant of static locking, adapted for real time and more than one processor. It is assumed that transactions arrive according to a Poisson process, execution times of transactions are independent and exponentially distributed and all transactions use the same number of data items. The system is then represented as a Markov model. A steady state is derived from this model. By examining the path through the system of a single transaction, a recursive relation that describes all moments of a transaction's response time is derived. The response time distribution is approximated by fitting a distribution to the first two moments. Simulation shows that this approximation gives excellent results.