The gated cascade diffusion model: An integrated theory of decision making, motor preparation, and motor execution.

This article introduces an integrated and biologically inspired theory of decision making, motor preparation, and motor execution. The theory is formalized as an extension of the diffusion model, in which diffusive accumulated evidence from the decision-making process is continuously conveyed to motor areas of the brain that prepare the response, where it is smoothed by a mechanism that approximates a Kalman-Bucy filter. The resulting motor preparation variable is gated prior to reaching agonist muscles until it exceeds a particular level of activation. We tested this gated cascade diffusion model by continuously probing the electrical activity of the response agonists through electromyography in four choice tasks that span a variety of domains in cognitive sciences, namely motion perception, numerical cognition, recognition memory, and lexical knowledge. The model provided a good quantitative account of behavioral and electromyographic data and systematically outperformed previous models. This work represents an advance in the integration of processes involved in simple decisions and sheds new light on the interplay between decision and motor systems. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Towards formal models of inhibitory mechanisms involved in motor imagery: a commentary on Bach et al. (2022).

A vast body of research suggests that the primary motor cortex is involved in motor imagery. This raises the issue of inhibition: how is it possible for motor imagery not to lead to motor execution? Bach et al. (Psychol Res Psychol Forschung. 10.1007/s00426-022-01773-w, 2022, this issue) suggest that the motor execution threshold may be "upregulated" during motor imagery to prevent execution. Alternatively, it has been proposed that, in parallel to excitatory mechanisms, inhibitory mechanisms may be actively suppressing motor output during motor imagery. These theories are verbal in nature, with well-known limitations. Here, we describe a toy-model of the inhibitory mechanisms thought to be at play during motor imagery to start disentangling predictions from competing hypotheses.

Motivational and cognitive predictors of apathy after subthalamic nucleus stimulation in Parkinson's disease.

Postoperative apathy is a frequent symptom in Parkinson's disease patients who have undergone bilateral deep brain stimulation of the subthalamic nucleus. Two main hypotheses for postoperative apathy have been suggested: (i) dopaminergic withdrawal syndrome relative to postoperative dopaminergic drug tapering; and (ii) direct effect of chronic stimulation of the subthalamic nucleus. The primary objective of our study was to describe preoperative and 1-year postoperative apathy in Parkinson's disease patients who underwent chronic bilateral deep brain stimulation of the subthalamic nucleus. We also aimed to identify factors associated with 1-year postoperative apathy considering: (i) preoperative clinical phenotype; (ii) dopaminergic drug management; and (iii) volume of tissue activated within the subthalamic nucleus and the surrounding structures. We investigated a prospective clinical cohort of 367 patients before and 1 year after chronic bilateral deep brain stimulation of the subthalamic nucleus. We assessed apathy using the Lille Apathy Rating Scale and carried out a systematic evaluation of motor, cognitive and behavioural signs. We modelled the volume of tissue activated in 161 patients using the Lead-DBS toolbox and analysed overlaps within motor, cognitive and limbic parts of the subthalamic nucleus. Of the 367 patients, 94 (25.6%) exhibited 1-year postoperative apathy: 67 (18.2%) with 'de novo apathy' and 27 (7.4%) with 'sustained apathy'. We observed disappearance of preoperative apathy in 22 (6.0%) patients, who were classified as having 'reversed apathy'. Lastly, 251 (68.4%) patients had neither preoperative nor postoperative apathy and were classified as having 'no apathy'. We identified preoperative apathy score [odds ratio (OR) 1.16; 95% confidence interval (CI) 1.10, 1.22; P < 0.001], preoperative episodic memory free recall score (OR 0.93; 95% CI 0.88, 0.97; P = 0.003) and 1-year postoperative motor responsiveness (OR 0.98; 95% CI 0.96, 0.99; P = 0.009) as the main factors associated with postoperative apathy. We showed that neither dopaminergic dose reduction nor subthalamic stimulation were associated with postoperative apathy. Patients with 'sustained apathy' had poorer preoperative fronto-striatal cognitive status and a higher preoperative action initiation apathy subscore. In these patients, apathy score and cognitive status worsened postoperatively despite significantly lower reduction in dopamine agonists (P = 0.023), suggesting cognitive dopa-resistant apathy. Patients with 'reversed apathy' benefited from the psychostimulant effect of chronic stimulation of the limbic part of the left subthalamic nucleus (P = 0.043), suggesting motivational apathy. Our results highlight the need for careful preoperative assessment of motivational and cognitive components of apathy as well as executive functions in order to better prevent or manage postoperative apathy.

Imbalanced motivated behaviors according to motor sign asymmetry in drug-naïve Parkinson's disease.

Few studies have considered the influence of motor sign asymmetry on motivated behaviors in de novo drug-naïve Parkinson's disease (PD). We tested whether motor sign asymmetry could be associated with different motivated behavior patterns in de novo drug-naïve PD. We performed a cross-sectional study in 128 de novo drug-naïve PD patients and used the Ardouin Scale of Behavior in Parkinson's disease (ASBPD) to assess a set of motivated behaviors. We assessed motor asymmetry based on (i) side of motor onset and (ii) MDS-UPDRS motor score, then we compared right hemibody Parkinson's disease to left hemibody Parkinson's disease. According to the MDS-UPDRS motor score, patients with de novo right hemibody PD had significantly lower frequency of approach behaviors (p = 0.031), including nocturnal hyperactivity (p = 0.040), eating behavior (p = 0.040), creativity (p = 0.040), and excess of motivation (p = 0.017) than patients with de novo left hemibody PD. Patients with de novo left hemibody PD did not significantly differ from those with de novo right hemibody PD regarding avoidance behaviors including apathy, anxiety and depression. Our findings suggest that motor sign asymmetry may be associated with an imbalance between motivated behaviors in de novo drug-naïve Parkinson's disease.

The Role of a Dopamine-Dependent Limbic-Motor Network in Sensory Motor Processing in Parkinson Disease.

Limbic and motor integration is enabled by a mesial temporal to motor cortex network. Parkinson disease (PD) is characterized by a loss of dorsal striatal dopamine but relative preservation of mesolimbic dopamine early in disease, along with changes to motor action control. Here, we studied 47 patients with PD using the Simon conflict task and [18F]fallypride PET imaging. Additionally, a cohort of 16 patients participated in a single-blinded dextroamphetamine (dAMPH) study. Task performance was evaluated using the diffusion model for conflict tasks, which allows for an assessment of interpretable action control processes. First, a voxel-wise examination disclosed a negative relationship, such that longer non-decision time is associated with reduced D2-like binding potential (BPND) in the bilateral putamen, left globus pallidus, and right insula. Second, an ROI analysis revealed a positive relationship, such that shorter non-decision time is associated with reduced D2-like BPND in the amygdala and ventromedial OFC. The difference in non-decision time between off-dAMPH and on-dAMPH trials was positively associated with D2-like BPND in the globus pallidus. These findings support the idea that dysfunction of the traditional striatal-motor loop underlies action control deficits but also suggest that a compensatory parallel limbic-motor loop regulates motor output.

Apathy in Parkinson's Disease: Clinical Patterns and Neurobiological Basis.

Apathy is commonly defined as a loss of motivation leading to a reduction in goal-directed behaviors. This multidimensional syndrome, which includes cognitive, emotional and behavioral components, is one of the most prevalent neuropsychiatric features of Parkinson's disease (PD). It has been established that the prevalence of apathy increases as PD progresses. However, the pathophysiology and anatomic substrate of this syndrome remain unclear. Apathy seems to be underpinned by impaired anatomical structures that link the prefrontal cortex with the limbic system. It can be encountered in the prodromal stage of the disease and in fluctuating PD patients receiving bilateral chronic subthalamic nucleus stimulation. In these stages, apathy may be considered as a disorder of motivation that embodies amotivational behavioral syndrome, is underpinned by combined dopaminergic and serotonergic denervation and is dopa-responsive. In contrast, in advanced PD patients, apathy may be considered as cognitive apathy that announces cognitive decline and PD dementia, is underpinned by diffuse neurotransmitter system dysfunction and Lewy pathology spreading and is no longer dopa-responsive. In this review, we discuss the clinical patterns of apathy and their treatment, the neurobiological basis of apathy, the potential role of the anatomical structures involved and the pathways in motivational and cognitive apathy.

A model-based approach to disentangling facilitation and interference effects in conflict tasks.

Conflict tasks have become one of the most dominant paradigms within cognitive psychology, with their key finding being the conflict effect: That participants are slower and less accurate when task-irrelevant information conflicts with task-relevant information (i.e., incompatible trials), compared to when these sources of information are consistent (i.e., compatible trials). However, the conflict effect can consist of two separate effects: Facilitation effects, which is the amount of benefit provided by consistent task-irrelevant information, and interference effects, which is the amount of impairment caused by conflicting task-irrelevant information. While previous studies have attempted to disentangle these effects using neutral trials, which contrast compatible and incompatible trials to trials that are designed to have neutral task-irrelevant information, these analyses rely on the assumptions of Donder's subtractive method, which are difficult to verify and may be violated in some circumstances. Here, we develop a model-based approach for disentangling facilitation and interference effects, which extends the existing diffusion model for conflict tasks (DMC) framework to allow for different levels of automatic activation in compatible and incompatible trials. Comprehensive parameter recovery assessments display the robust measurement properties of our model-based approach, which we apply to nine previous data sets from the flanker (6) and Simon (3) tasks. Our findings suggest asymmetric facilitation and interference effects, where interference effects appear to be present for most participants across most studies, whereas facilitation effects appear to be small or nonexistent. We believe that our novel model-based approach provides an important step forward for understanding how information processing operates in conflict tasks, allowing researchers to assess the convergence or divergence between experimental-based (i.e., neutral trials) and model-based approaches when investigating facilitation and interference effects. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Speeding-up while growing-up: Synchronous functional development of motor and non-motor processes across childhood and adolescence.

Describing the maturation of information processing in children is fundamental for developmental science. Although non-linear changes in reaction times have been well-documented, direct measurement of the development of the different processing components is lacking. In this study, electromyography was used to quantify the maturation of premotor and motor processes on a sample of 114 children (6-14 years-old) and 15 adults. Using a model-based approach, we show that the development of these two components is well-described by an exponential decrease in duration, with the decay rate being equal for the two components. These findings provide the first unbiased evidence in favour of the common developmental rate of nonmotor and motor processes by directly confronting rates of development of different processing components within the same task. This common developmental rate contrasts with the differential physical maturation of region-specific cerebral gray and white matter. Tentative paths of interpretation are proposed in the discussion.

An integrated theory of deciding and acting.

This article presents a theory in which motor execution in perceptual decision-making tasks is determined by the same evolving decision variable that drives response time. The theory builds upon recent insights from the neuroscience of decision-making and motor control. It is formalized as an extension of Ratcliff's diffusion model, and assumes that two thresholds operate on the evidence accumulation decision variable. The first threshold, referred to as electromyographic (EMG) threshold, marks the onset of electrical activity in the response-relevant muscle and the beginning of force production. The second threshold corresponds to the response. The theory makes several benchmark predictions. Notably, the mean duration of motor execution, as quantified by the mean latency between EMG onset and the response, should depend on the rate of evidence accumulation, and should thus increase as the perceptual difficulty of the task increases. We tested these predictions in a paradigmatic perceptual decision-making task, the random dot motion task, and recorded the EMG activity of response-relevant muscles. The behavioral and EMG data provide very strong evidence for each prediction. A final quantitative evaluation of the model showed good fits to these data. The theory resolves conflicting findings in the fields of mathematical psychology, motor control, and decision neurosciences. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Semantic and action tool knowledge in the brain: Identifying common and distinct networks.

Most cognitive models of apraxia assume that impaired tool use results from a deficit occurring at the conceptual level, which contains dedicated information about tool use, namely, semantic and action tool knowledge. Semantic tool knowledge contains information about the prototypical use of familiar tools, such as function (e.g., a hammer and a mallet share the same purpose) and associative relations (e.g., a hammer goes with a nail). Action tool knowledge contains information about how to manipulate tools, such as hand posture and kinematics. The present review aimed to better understand the neural correlates of action and semantic tool knowledge, by focusing on activation, stimulation and patients' studies (left brain-damaged patients). We found that action and semantic tool knowledge rely upon a large brain network including temporal and parietal regions. Yet, while action tool knowledge calls into play the intraparietal sulcus, function relations mostly involve the anterior and posterior temporal lobe. Associative relations engaged the angular and the posterior middle temporal gyrus. Moreover, we found that hand posture and kinematics both tapped into the inferior parietal lobe and the lateral occipital temporal cortex, but no region specificity was found for one or the other representation. Our results point out the major role of both posterior middle temporal gyrus and inferior parietal lobe for action and semantic tool knowledge. They highlight the common and distinct brain networks involved in action and semantic tool networks and spur future directions on this topic.

A diffusion model analysis of the effects of aging in the Flanker Task.

The diffusion decision model (DDM) has been used to investigate the effects of aging on information processing in simple response time (RT) tasks. These analyses have consistently shown that the age-related slowing of RTs can be accounted for by slower processing speed in sensorimotor systems and more cautious responding. However, previous DDM assessments of aging have ignored conflict tasks (e.g., the flanker task), the dominant paradigm for investigating age-related differences in executive control, as the DDM is unable to combine task-relevant and task-irrelevant stimulus information. Our study used two recently developed extensions of the DDM-the diffusion model for conflict tasks (DMC) and the shrinking spotlight diffusion model (SSP)-to provide the first model-based assessment of age-related differences in a flanker task featuring a manipulation of the spacing between target and flanking letters. Consistent with previous findings, older adults were globally slower than younger adults, and the magnitude of the flanker effect was larger for older than younger adults only when the spacing between the target and flanking letters was small. Fits of the models to data revealed a superiority of the DMC over the SSP. The DMC accounts for experimental findings with a 62-ms slowing of the nondecision component of RT for older compared to younger adults, a more cautious decision criterion, and enhanced processing of the target and flanking letters in the near periphery, suggesting a stronger attentional engagement in the task. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

A measure of the interference effect distribution.

We elaborated an index, the Interference Distribution Index, which allows quantifying the relation between response times and the size of the interference effect. This index is associated with an intuitive graphical representation, the Lorenz-interference plot. We show that this index has some convenient properties in terms of sensitivity to changes in the distribution of the interference effect and to aggregation of individual data. Moreover, it turns out that this index is the only one (up to an arbitrary increasing transformation) possessing these properties. The relevance of this index is illustrated through simulations of a cognitive model of interference effects and reanalysis of experimental data.

A comparison of conflict diffusion models in the flanker task through pseudolikelihood Bayes factors.

Conflict tasks are one of the most widely studied paradigms within cognitive psychology, where participants are required to respond based on relevant sources of information while ignoring conflicting irrelevant sources of information. The flanker task, in particular, has been the focus of considerable modeling efforts, with only 3 models being able to provide a complete account of empirical choice response time distributions: the dual-stage 2-phase model (DSTP), the shrinking spotlight model (SSP), and the diffusion model for conflict tasks (DMC). Although these models are grounded in different theoretical frameworks, can provide diverging measures of cognitive control, and are quantitatively distinguishable, no previous study has compared all 3 of these models in their ability to account for empirical data. Here, we perform a comparison of the precise quantitative predictions of these models through Bayes factors, using probability density approximation to generate a pseudolikelihood estimate of the unknown probability density function, and thermodynamic integration via differential evolution to approximate the analytically intractable Bayes factors. We find that for every participant across 3 data sets from 3 separate research groups, DMC provides an inferior account of the data to DSTP and SSP, which has important theoretical implications regarding cognitive processes engaged in the flanker task, and practical implications for applying the models to flanker data. More generally, we argue that our combination of probability density approximation with marginal likelihood approximation-which we term pseudolikelihood Bayes factors-provides a crucial step forward for the future of model comparison, where Bayes factors can be calculated between any models that can be simulated. We also discuss the limitations of simulation-based methods, such as the potential for approximation error, and suggest that researchers should use analytically or numerically computed likelihood functions when they are available and computationally tractable. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Dynamics of attentional focusing in the Eriksen flanker task.

Eriksen and Eriksen (Perception & Psychophysics, 16, 143-149, 1974) explained the flanker compatibility effect in terms of response competition. A simplified version of the original flanker task, featuring a 1-to-1 mapping of stimuli onto responses, has become prominent in the literature. Compatible flanker trials present identical items (HHHHH), whereas incompatible trials present different items (HHSHH). The 1-to-1 mapping is potentially problematic because it invites a strategy that people could use to perform the task. Subjects could first determine whether all the items are the same and focus attention on the central target only if they are not. Response times (RTs) would be longer for incompatible trials partly because they require the extra step of focusing attention. We tested this conditional focusing hypothesis by combining a 1-to-1 flanker task with a digit probe detection procedure. In half of the trials, the digit '7' appeared immediately after the response to the flanker display, at the target or a flanker location. Three experiments showed a V-shaped function of RTs to digits across locations that was not modulated by flanker compatibility. These results demonstrate that subjects focused attention on the central target regardless of the same/different configuration of the display, refuting the conditional focusing hypothesis. Our findings support Eriksen and Eriksen's original interpretation of the flanker task.

Neurally constrained modeling of speed-accuracy tradeoff during visual search: gated accumulation of modulated evidence.

Stochastic accumulator models account for response times and errors in perceptual decision making by assuming a noisy accumulation of perceptual evidence to a threshold. Previously, we explained saccade visual search decision making by macaque monkeys with a stochastic multiaccumulator model in which accumulation was driven by a gated feed-forward integration to threshold of spike trains from visually responsive neurons in frontal eye field that signal stimulus salience. This neurally constrained model quantitatively accounted for response times and errors in visual search for a target among varying numbers of distractors and replicated the dynamics of presaccadic movement neurons hypothesized to instantiate evidence accumulation. This modeling framework suggested strategic control over gate or over threshold as two potential mechanisms to accomplish speed-accuracy tradeoff (SAT). Here, we show that our gated accumulator model framework can account for visual search performance under SAT instructions observed in a milestone neurophysiological study of frontal eye field. This framework captured key elements of saccade search performance, through observed modulations of neural input, as well as flexible combinations of gate and threshold parameters necessary to explain differences in SAT strategy across monkeys. However, the trajectories of the model accumulators deviated from the dynamics of most presaccadic movement neurons. These findings demonstrate that traditional theoretical accounts of SAT are incomplete descriptions of the underlying neural adjustments that accomplish SAT, offer a novel mechanistic account of decision-making mechanisms during speed-accuracy tradeoff, and highlight questions regarding the identity of model and neural accumulators. NEW & NOTEWORTHY A gated accumulator model is used to elucidate neurocomputational mechanisms of speed-accuracy tradeoff. Whereas canonical stochastic accumulators adjust strategy only through variation of an accumulation threshold, we demonstrate that strategic adjustments are accomplished by flexible combinations of both modulation of the evidence representation and adaptation of accumulator gate and threshold. The results indicate how model-based cognitive neuroscience can translate between abstract cognitive models of performance and neural mechanisms of speed-accuracy tradeoff.

Conflict processing in kindergarten children: New evidence from distribution analyses reveals the dynamics of incorrect response activation and suppression.

The development of cognitive control is known to follow a long and protracted development. However, whether the interference effect in conflict tasks in children would entail the same core processes as in adults, namely an automatic activation of incorrect response and its subsequent suppression, remains an open question. We applied distributional analyses to reaction times and accuracy of 5- and 6-year-old children performing three conflict tasks (flanker, Simon, and Stroop) in a within-participants design. This revealed both strong commonalities and differences between children and adults. As in adults, fast responses were more error prone than slow ones on incompatible trials, indicating a fast "automatic" activation of the incorrect response. In addition, the strength of this activation differed across tasks, following a pattern similar to that of adults. Moreover, modeling the data with a drift diffusion model adapted for conflict tasks allowed one to better assess the origin of the typical slowing down observed in children. Besides showing that advanced distribution analyses can be successfully applied to children, the current results support the notion that interference effects in 5- and 6-year-olds are driven by mechanisms very similar to the ones at play in adults but with different time courses.

Neural mechanisms of speed-accuracy tradeoff of visual search: saccade vigor, the origin of targeting errors, and comparison of the superior colliculus and frontal eye field.

Balancing the speed-accuracy tradeoff (SAT) is necessary for successful behavior. Using a visual search task with interleaved cues emphasizing speed or accuracy, we recently reported diverse contributions of frontal eye field (FEF) neurons instantiating salience evidence and response preparation. Here, we report replication of visual search SAT performance in two macaque monkeys, new information about variation of saccade dynamics with SAT, extension of the neurophysiological investigation to describe processes in the superior colliculus (SC), and a description of the origin of search errors in this task. Saccade vigor varied idiosyncratically across SAT conditions and monkeys but tended to decrease with response time. As observed in the FEF, speed-accuracy tradeoff was accomplished through several distinct adjustments in the superior colliculus. In "Accurate" relative to "Fast" trials, visually responsive neurons in SC as in FEF had lower baseline firing rates and later target selection. The magnitude of these adjustments in SC was indistinguishable from that in FEF. Search errors occurred when visual salience neurons in the FEF and the SC treated distractors as targets, even in the Accurate condition. Unlike FEF, the magnitude of visual responses in the SC did not vary across SAT conditions. Also unlike FEF, the activity of SC movement neurons when saccades were initiated was equivalent in Fast and Accurate trials. Saccade-related neural activity in SC, but not FEF, varied with saccade peak velocity. These results extend our understanding of the cortical and subcortical contributions to SAT. NEW & NOTEWORTHY Neurophysiological mechanisms of speed-accuracy tradeoff (SAT) have only recently been investigated. This article reports the first replication of SAT performance in nonhuman primates, the first report of variation of saccade dynamics with SAT, the first description of superior colliculus contributions to SAT, and the first description of the origin of errors during SAT. These results inform and constrain new models of distributed decision making.

A model-based quantification of action control deficits in Parkinson's disease.

Basal ganglia dysfunction in Parkinson's disease (PD) is thought to generate deficits in action control, but the characterization of these deficits have been qualitative rather than quantitative. Patients with PD typically show prolonged response times on tasks that instantiate a conflict between goal-directed processing and automatic response tendencies. In the Simon task, for example, the irrelevant location of the stimulus automatically activates a corresponding lateralized response, generating a potential conflict with goal-directed choices. We applied a new computational model of conflict processing to two sets of behavioral data from the Simon task to quantify the effects of PD and dopaminergic (DA) medication on action control mechanisms. Compared to healthy controls (HC) matched in age gender and education, patients with PD showed a deficit in goal-directed processing, and the magnitude of this deficit positively correlated with cognitive symptoms. Analyses of the time-course of the location-based automatic activation yielded mixed findings. In both datasets, we found that the peak amplitude of the automatic activation was similar between PD and HC, demonstrating a similar degree of response capture. However, PD patients showed a prolonged automatic activation in only one dataset. This discrepancy was resolved by theoretical analyses of conflict resolution in the Simon task. The reduction of interference generated by the automatic activation appears to be driven by a mixture of passive decay and top-down inhibitory control, the contribution of each component being modulated by task demands. Our results suggest that PD selectively impairs the inhibitory control component, a deficit likely remediated by DA medication. This work advances our understanding of action control deficits in PD, and illustrates the benefit of using computational models to quantitatively measure cognitive processes in clinical populations.

Neural bases of automaticity.

Automaticity allows us to perform tasks in a fast, efficient, and effortless manner after sufficient practice. Theories of automaticity propose that across practice processing transitions from being controlled by working memory to being controlled by long-term memory retrieval. Recent event-related potential (ERP) studies have sought to test this prediction, however, these experiments did not use the canonical paradigms used to study automaticity. Specifically, automaticity is typically studied using practice regimes with consistent mapping between targets and distractors and spaced practice with individual targets, features that these previous studies lacked. The aim of the present work was to examine whether the practice-induced shift from working memory to long-term memory inferred from subjects' ERPs is observed under the conditions in which automaticity is traditionally studied. We found that to be the case in 3 experiments, firmly supporting the predictions of theories. In addition, we found that the temporal distribution of practice (massed vs. spaced) modulates the shape of learning curves. The ERP data revealed that the switch to long-term memory is slower for spaced than massed practice, suggesting that memory systems are used in a strategic manner. This finding provides new constraints for theories of learning and automaticity. (PsycINFO Database Record

ELF: A new measure of response capture.

Response capture is a widespread and extensively studied phenomenon, in particular in decision tasks involving response conflict. Its intensity is routinely quantified by conditional accuracy function (CAF). We argue that this method might be misleading, and propose an alternative approach, the error location function (ELF). While CAF provides the error rate by bins of reaction time (RT), ELF represents the share of total errors below each quantile of RT. We derive from ELF an index of response capture, the error location index (ELI), which represents the area below the ELF. Using simulations of computational models, we show that ELF and ELI specifically quantify variations in response capture. Finally, we illustrate the usefulness of ELF and ELI through experimental data and show that ELF and CAF can yield to contradictory conclusions.