Motivational and cognitive determinants of control during conflict processing

Previous studies suggest that both reward anticipation and expected or experienced conflicts activate cognitive control. The present study investigated how these factors interact during conflict processing. In two experiments, participants performed a variant of the Stroop task, receiving performance-dependent monetary rewards in some blocks. In addition, we manipulated the level of conflict-triggered reactive and expectancy-driven proactive control: In Experiment 1, we compared the Stroop effect after previously congruent and incongruent trials to examine the conflict adaptation effect (reactive control). We found that the level of motivation did not interact with conflict adaptation. In Experiment 2, we varied the proportion of congruent and incongruent trials to manipulate conflict expectancy (proactive control). The data suggest the effects of motivation to be less pronounced under conditions of high conflict expectancy. We conclude that the interaction of motivation with cognitive determinants of control depends on whether these activate proactive or reactive control processes.     

Tracking the Time Course of Word‐Frequency Effects in Auditory Word Recognition With Event‐Related Potentials

Although the word‐frequency effect is one of the most established findings in spoken‐word recognition, the precise processing locus of this effect is still a topic of debate. In this study, we used event‐related potentials (ERPs) to track the time course of the word‐frequency effect. In addition, the neighborhood density effect, which is known to reflect mechanisms involved in word identification, was also examined. The ERP data showed a clear frequency effect as early as 350 ms from word onset on the P350, followed by a later effect at word offset on the late N400. A neighborhood density effect was also found at an early stage of spoken‐word processing on the PMN, and at word offset on the late N400. Overall, our ERP differences for word frequency suggest that frequency affects the core processes of word identification starting from the initial phase of lexical activation and including target word selection. They thus rule out any interpretation of the word frequency effect that is limited to a purely decisional locus after word identification has been completed.     

Reliability and plasticity of response inhibition and interference control

This study investigated the internal reliability, temporal stability and plasticity of commonly used measures of inhibition-related functions. Stop-signal, go/no-go, antisaccade, Simon, Eriksen flanker, Stroop and Continuous Performance tasks were administered twice to 23 healthy participants over a period of approximately 11 weeks in order to assess test–retest correlations, internal consistency (Cronbach’s alpha), and systematic between as well as within session performance changes. Most of the inhibition-related measures showed good test–retest reliabilities and internal consistencies, with the exception of the stop-signal reaction time measure, which showed poor reliability. Generally no systematic performance changes were observed across the two assessments with the exception of four variables of the Eriksen flanker, Simon and Stroop task which showed reduced variability of reaction time and an improvement in the response time for incongruent trials at second assessment. Predominantly stable performance within one test session was shown for most measures. Overall, these results are informative for studies with designs requiring temporally stable parameters e.g. genetic or longitudinal treatment studies.     

Conditional automaticity in subliminal morphosyntactic priming

We used a gender-classification task to test the principles of subliminal morphosyntactic priming. In Experiment 1, masked, subliminal feminine or masculine articles were used as primes. They preceded a visible target noun. Subliminal articles either had a morphosyntactically congruent or incongruent gender with the targets. In a gender-classification task of the target nouns, subliminal articles primed the responses: responses were faster in congruent than incongruent conditions (Experiment 1). In Experiment 2, we tested whether this congruence effect depended on gender relevance. In line with a relevance-dependence, the congruence effect only occurred in a gender-classification task but was absent in another categorical discrimination of the target nouns (Experiment 2). The congruence effect also depended on correct word order. It was diminished when nouns preceded articles (Experiment 3). Finally, the congruence effect was replicated with a larger set of targets but only for masculine targets (Experiment 4). Results are discussed in light of theories of subliminal priming in general and of subliminal syntactic priming in particular.     

Cognitive Functioning,Behavior, and Quality of Life After Stroke in Childhood

Rationale: To provide a better understanding of cognitive functioning, motor outcome, behavior and quality of life after childhood stroke and to study the relationship between variables expected to influence rehabilitation and outcome (age at stroke, time elapsed since stroke, lateralization, location and size of lesion).

Methods: Children who suffered from stroke between birth and their eighteenth year of life underwent an assessment consisting of cognitive tests (WISC-III, WAIS-R, K-ABC, TAP, Rey-Figure, German Version of the CVLT) and questionnaires (Conner's Scales, KIDSCREEN).

Results: Twenty-one patients after stroke in childhood (15 males, mean 11;11 years, SD 4;3, range 6;10–21;2) participated in the study. Mean Intelligence Quotients (IQ) were situated within the normal range (mean Full Scale IQ 96.5, range IQ 79–129). However, significantly more patients showed deficits in various cognitive domains than expected from a healthy population (Performance IQ p?=?.000; Digit Span p?=?.000, Arithmetic's p?=?.007, Divided Attention p?=?.028, Alertness p?=?.002). Verbal IQ was significantly better than Performance IQ in 13 of 17 patients, independent of the hemispheric side of lesion. Symptoms of ADHD occurred more often in the patients' sample than in a healthy population (learning difficulties/inattention p?=?.000; impulsivity/hyperactivity p?=?.006; psychosomatics p?=?.006). Certain aspects of quality of life were reduced (autonomy p?=?.003; parents' relation p?=?.003; social acceptance p?=?.037). Three patients had a right-sided hemiparesis, mean values of motor functions of the other patients were slightly impaired (sequential finger movements p?=?.000, hand alternation p?=?.001, foot tapping p?=?.043). In patients without hemiparesis, there was no relation between the lateralization of lesion and motor outcome. Lesion that occurred in the midst of childhood (5–10 years) led to better cognitive outcome than lesion in the very early (0–5 years) or late childhood (10–18 years). Other variables such as presence of seizure, elapsed time since stroke and size of lesion had a small to no impact on prognosis.

Conclusion: Moderate cognitive and motor deficits, behavioral problems, and impairment in some aspects of quality of life frequently remain after stroke in childhood. Visuospatial functions are more often reduced than verbal functions, independent of the hemispheric side of lesion. This indicates a functional superiority of verbal skills compared to visuospatial skills in the process of recovery after brain injury. Compared to the cognitive outcome following stroke in adults, cognitive sequelae after childhood stroke do indicate neither the lateralization nor the location of the lesion focus. Age at stroke seems to be the only determining factor influencing cognitive outcome.     

Spatial Simon effects and compatibility effects induced by observed gaze direction

Preconditions for the processing of observed gaze direction were studied by spatial Simon and compatibility effects. In five experiments, responses in the direction of a gaze were faster than responses in the opposite direction. Gaze direction influenced response speed although its processing was not required (Experiments 1, 2, 4, and 5). The result supports the notion of an inclination to process observed gaze direction in humans. However, the processes underlying the Simon effect of observed gaze direction were relatively time-consuming: Simon effects induced by gaze direction increased with response speed. Focusing of attention seemed to be part of the necessary processes: Simon effects were eliminated if attention was focused away from the eyes (Experiment 2). Further, if the processing of observed gaze direction was required, Simon effects by faces' observer-relative screen positions were absent (Experiment 3). Control conditions revealed that Simon effects by gaze direction can be produced with faces tilted by 90°, but that corresponding Simon effects do not result from numerical stimuli with an analogue spatial structure (Experiment 4), and that Simon effects result from gaze directions of scrambled faces (Experiment 5).     

Effects of extensive dual-task practice on processing stages in simultaneous choice tasks

Schumacher et al. Psychological Science 12:101–108, (2001) demonstrated the elimination of most dual-task costs (“perfect time-sharing”) after extensive dual-task practice of a visual and an auditory task in combination. For the present research, we used a transfer methodology to examine this practice effect in more detail, asking what task-processing stages were sped up by this dual-task practice. Such research will be essential to specify mechanisms associated with the practice-related elimination of dual-task costs. In three experiments, we introduced postpractice transfer probes focusing on the perception, central response-selection, and final motor-response stages. The results indicated that the major change achieved by dual-task practice was a speed-up in the central response-selection stages of both tasks. Additionally, perceptual-stage shortening of the auditory task was found to contribute to the improvements in time-sharing. For a better understanding of such time-sharing, we discuss the contributions of the present findings in relation to models of practiced dual-task performance.     

Is there an age deficit in the selection of mental sets?

Efficient selection of actions is dependent on higher-level constraints (mental sets) on lower-level selection. This paper explores the hypothesis that ageing leads to specific impairments associated with higher-level selection between mental sets. Indirect evidence for such a deficit comes from occasional findings of age differences in situations with high executive-control demands (e.g., Mayr & Kliegl, 1993) that are not easily explained in terms of other factors, such as general slowing or working memory parameters. More direct evidence comes from recent results with the so-called task-switching paradigm. Specifically, age-sensitive set-selection processes are indicated by age differences in “global selection costs” (i.e., the response-time difference between task-switching blocks and single-task blocks) which seem to be particularly large when demands in terms of “keeping competing mental sets apart” are high. Finally, data from a new variant of the task-switching paradigm (the “fade-out paradigm”) are reported which show that age differences in global costs persist substantially beyond a phase in which set-selection is actually necessary. Generally, evidence is consistent with the view that in older age, a costly set-selection mode of processing dominates over the more efficient within-set-selection mode of processing, possibly because of a problem with maintaining distinct representations of what ought to be done in the face of competing representations of what could be done in principle.