Florian Schmitz

Process components of the Implicit Association Test: a diffusion-model analysis.

The authors present a diffusion-model analysis of the Implicit Association Test (IAT). In Study 1, the IAT effect was decomposed into 3 dissociable components: Relative to the compatible phase, (a) ease and speed of information accumulation are lowered in the incompatible phase, (b) more cautious speed-accuracy settings are adopted, and (c) nondecision components of processing require more time. Studies 2 and 3 assessed the nature of interindividual differences in these components. Construct-specific variance in the IAT relating to the construct to be measured (such as implicit attitudes) was concentrated in the compatibility effect on information accumulation (Studies 2 and 3), whereas systematic method variance in the IAT was mapped on differential speed-accuracy settings (Study 3). Implications of these dissociations for process theories of the IAT and for applications are discussed.

Behavioral Components of Impulsivity

Acting in accord with long-term goals requires control of interfering impulses, the success of which depends on several different processes. Using a structural-equation modeling approach, we investigated 5 behavioral components of impulsivity: the control of stimulus interference, proactive interference, and response interference, as well as decisional and motivational impulsivity. Results support the existence of 5 correlated but separable components of impulsive behavior. The present study is the 1st to demonstrate the separability of stimulus and response interference. It also supports the notion that control of response-related interference is not a unitary construct: Response-selection demands were separable from those of withholding or stopping. Relations between behavioral impulsivity components and self-report measures of impulsivity were largely absent. We conclude that as the construct of impulsivity has been extended to describe an increasingly diverse set of phenomena and processes, it has become too broad to be helpful in guiding future research.

Understanding the role of executive control in the Implicit Association Test: Why flexible people have small IAT effects:

The goal of the present research was to investigate the role of three central-executive functions—switching of mental sets, inhibition of prepotent responses, and simultaneous storage and processing (i.e., working-memory capacity)—in accounting for method variance in the Implicit Association Test (IAT). In two studies, several IATs with unrelated contents were administered along with a battery of central-executive tasks, with multiple tasks tapping each of the above executive functions. Method variance was found to be related to the switching factor, but not to the inhibition factor. There was also evidence for a small independent contribution of the working-memory capacity factor. The findings constrain process accounts of the IAT, lending support to an account in terms of task-set switching, and they have consequences for applications.

General and food-specific inhibitory deficits in binge eating disorder

OBJECTIVEnTo investigate behavioral inhibition in individuals with binge eating disorder (BED) compared with overweight and obese individuals without BED (No-BED).nnnMETHODnParticipants with BED (n = 31) and the weight-matched No-BED group (n = 29) completed an inhibitory control task (stop-signal task, SST) with food and neutral stimuli.nnnRESULTSnThe BED group needed more time to stop an ongoing response, as indicated by increased stop signal reaction time (SSRT) relative to the No-BED group. Additionally, compared with the No-BED group, the BED group displayed more difficulty inhibiting responses elicited by food stimuli. The deficits in behavioral response inhibition were also found to be related to the severity of reported symptoms.nnnDISCUSSIONnThere is a general deficit in late stage behavioral inhibition in BED, and this may be particularly pronounced in the context of food stimuli.

Decomposing task-switching costs with the diffusion model.

In four experiments, task-switching processes were investigated with variants of the alternating runs paradigm and the explicit cueing paradigm. The classical diffusion model for binary decisions (Ratcliff, 1978) was used to dissociate different components of task-switching costs. Findings can be reconciled with the view that task-switching processes take place in successive phases as postulated by multiple-components models of task switching (e.g., Mayr & Kliegl, 2003; Ruthruff, Remington, & Johnston, 2001). At an earlier phase, task-set reconfiguration (Rogers & Monsell, 1995) or cue-encoding (Schneider & Logan, 2005) takes place, at a later phase, the response is selected in accord with constraints set in the first phase. Inertia effects (Allport, Styles, & Hsieh, 1994; Allport & Wylie, 2000) were shown to affect this later stage. Additionally, findings support the notion that response caution contributes to both global as well as to local switching costs when task switches are predictable.

Attentional bias for food cues in binge eating disorder

The aim of the present study was to investigate an attentional bias toward food stimuli in binge eating disorder (BED). To this end, a BED and a weight-matched control group (CG) completed a clarification task and a spatial cueing paradigm. The clarification task revealed that food stimuli were faster detected than neutral stimuli, and that this difference was more pronounced in BED than in the CG. The spatial cueing paradigm indicated a stimulus engagement effect in the BED group but not in the CG, suggesting that an early locus in stimulus processing contributes to differences between BED patients and obese controls. Both groups experienced difficulty disengaging attention from food stimuli, and this effect was only descriptively larger in the BED group. The effects obtained in both paradigms were found to be correlated with reported severity of BED symptoms. Of note, this relationship was partially mediated by the arousal associated with food stimuli relative to neutral stimuli, as predicted by an account on incentive sensitization.

Age-Related Increases in Stroop Interference: Delineation of General Slowing Based on Behavioral and White Matter Analyses

The Stroop interference task is a widely used paradigm to examine cognitive inhibition, which is a key component of goal‐directed behavior. With increasing age, reaction times in the Stroop interference task are usually slowed. However, to date it is still under debate if age‐related increases in reaction times are merely an artifact of general slowing. The current study was conducted to investigate the role of general slowing, as measured by Trail‐Making‐Test‐A, in age‐related alterations of Stroop interference. We applied Diffusion Tensor Imaging (DTI) to determine the topography of neuronal networks underlying Stroop interference under control of general slowing. On the behavioral level, linear regression analysis demonstrated that age accounted for significant variance on Stroop interference, whereas TMT‐A performance did not. Controlling for TMT‐A, DTI based white matter analyses demonstrated a strong association of Stroop interference with integrity measures of genu of corpus callosum, bilateral anterior corona radiata, and bilateral anterior limb of capsula interna. These pathways are associated with frontal brain regions by either connecting the bilateral dorsolateral prefrontal cortex or the anterior cingulate cortex with frontal and subcortical regions or by containing fibers which are part of cortico‐thalamic circuits that cross prefrontal regions. Importantly, results expand our knowledge of the neural basis of Stroop interference and emphasize the importance of white matter integrity of frontal pathways in the modulation of Stroop interference. Combining behavioral and DTI findings our results further suggest that cognitive inhibition, as measured by Stroop task, is a qualitatively distinct cognitive process that declines with age. Hum Brain Mapp 35:2448–2458, 2014.

Components of task switching: A closer look at task switching and cue switching

Research using the diffusion model to decompose task-switching effects has contributed to a better understanding of the processes underlying the observed effect in the explicit task cueing paradigm: Previous findings could be reconciled with multiple component models of task switching or with an account on compound-cue retrieval/repetition priming. In the present study, we used two cues for each task in order to decompose task-switch and cue-switch effects. Response time data support previous findings that comparable parts of the switching effect can be attributed to cue-switching and task-switching. A diffusion model analysis of the data confirmed that non-decision time is increased and drift rates are decreased in unpredicted task-switches. Importantly, it was shown that non-decision time was selectively increased in task-switching trials but not in cue-switching trials. Results of the present study specifically support the notion of additional processes in task-switches and can be reconciled with broader multiple component accounts.

Cognitive interference and a food-related memory bias in binge eating disorder.

The present study was concerned with cognitive interference and a specific memory bias for eating-related stimuli in binge eating disorder (BED). Further objectives were to find out under which circumstances such effects would occur, and whether they are related with each other and with reported severity of BED symptoms. A group of women diagnosed with BED and a matched sample of overweight controls completed two paradigms, an n-back task with lures and a recent-probes task. The BED group generally experienced more interference in the n-back task. Additionally, they revealed selectively increased interference for food items in the recent-probes task. Findings can be reconciled with the view that control functions are generally impaired in BED, and that there is an additional bias for eating-related stimuli, both of which were related with reported severity of BED symptoms.

Impaired Early-Response Inhibition in Overweight Females with and without Binge Eating Disorder

Objective Several studies report increased reward sensitivity towards food in overweight individuals. By contrast, data is inconclusive with respect to response inhibition in overweight individuals without binge eating disorder (BED). Hence, the latter was addressed in the present study in a group of overweight/obese females with and without BED and a normal-weight control group without eating disorders. Method A group of women with BED (n = 29), a group of overweight women without BED (n = 33) and normal-weight females (n = 30) participated in a pictorial priming paradigm, with food items (relevant primes) and office utensils (neutral primes) and color blobs (neutral primes) as stimuli. Increased response priming effects (i.e. priming with switches between stimulus categories) were taken as indicators of deficient behavioral inhibition. Results Priming effects for neutral primes were moderate and comparable across all groups. However, primes associated with the food task set lead to increased priming effects in both overweight groups. But, effects were comparable for overweight/obese participants with and without BED. Discussion Results suggest that early response inhibition in the context of food is impaired in overweight individuals compared to normal-weight individuals.