Dual-task costs are calculated as the difference between Task 2 performance in dual-task
conditions and performance in single-task blocks [ 10 ]. The PRP effect reflects worse Task 2
performance in dual-task conditions with short SOAs than with long SOAs [ 9 ]. In contrast to the multitasking costs measured in task-switching contexts, there is so far no consensus about the underlying cognitive mechanisms (i.e., working memory updating, inhibition, and shift- ing) of performance costs arising in dual-task contexts. However, a recent study by Hirsch and colleagues (2018) suggests that dual-task costs reflect, like mixing costs, cognitive processes involved in maintaining and updating task sets in working memory [ 11 ]. Furthermore, this study provides first evidence indicating that the PRP effect might reflect at least partly pro- cesses related to the engagement and disengagement and/or inhibition of task sets.
Switching between tasks in complex work environments, dividing attention between cellphones and TVs or simultaneously handling complex car cockpits and driving – multitasking is omnipresent in modern society. In lab settings, performing multiple tasks simultaneously reliably leads to dual-task costs which are most often explained by structural or strategic bottlenecks (Meyer & Kieras, 1997; Pashler, 1994), capacity limitations (Damos & Wickens, 1980; Kahneman, 1973; Navon & Gopher, 1979; Wickens, 2008) or cross-talk (Navon & Miller, 1987; Swinnen & Wenderoth, 2004). However, some studies have seen reduced or even eliminated dual-task costs, either after large amounts of training (Ruthruff et al., 2006), or by using ideomotor-compatible tasks (Halvorson et al., 2013; Halvorson & Hazeltine, 2015). Künzell et al. (2018) argued that both large amounts of practice and ideomotor compatibility, make tasks more predictable which can facilitate automatic processing and reduce interference between tasks. Previous studies indeed found a beneficial effect of making one of two tasks predictable, although performance improvements were only visible in the predictable task. For instance, adding predictability to a tracking task improved tracking accuracy when simultaneously performed with an auditory reaction time task, but reaction times did not improve (Broeker et al. submitted; Ewolds, Broeker, Oliveira, Raab, & Künzell, 2017). To further elucidate the role of predictability in multitasking, Experiment 1 of our study aimed to elaborate on these previous findings. We investigated whether the simultaneous performance of two predictable tasks, as opposed to just one predictable task as in previous studies, would enhance dual-task performance in both tasks after single-task training on both tasks. Following the findings of Experiment 1, which indicated only task-specific effects of predictability, we decided to conduct Experiment 2, in which participants did dual-task training.
The findings have sparked a decades-long theoretical controversy about the role of cognitive control in dual-tasking. Cognitive control enables us to handle complex task demands in a flexible and context-dependent manner and thus to act in a goal-directed way. In dual-task contexts, cognitive control might be required, inter alia, for shielding the processing of each task from interfering influences resulting from the simultaneous processing of another task and for the temporal coordination of multiple task processing. Until today, it is disputed whether dual-task-related performance costs are behavioral markers of cognitive control, or whether they are solely attributable to structural limitations of the cognitive system. These limitations prohibit simultaneous response selection and lead to the situation that the responses for the two individual tasks performed within a dualtask are selected on a ‘first-come, first-served’ basis. Against this background, the main objective of the present cumulative dissertation was to re-examine the role of cognitive control in dual-tasking, thereby contributing to a better understanding of the mechanisms of cognitive control that underlie our ability to perform in an adaptive and goal-directed manner. To this end, two levels of dual-task processing on which cognitive control might act, namely the local level and the global level of dual-tasking, were investigated based on two lines of research.
Interestingly, previous research mainly focused on cog- nitive capacities to explain DT decrements. We were able to show a significant relationship between leg mus- cular capacity and DT walking performance as well. Thus, besides cognitive capacities, leg muscle functions seem to additionally affect DT walking performance in children. Given the association between LTM-LE and leg muscle mass , our regression analyses indicate that children with a higher amount of leg muscle mass show shorter step times with lower temporal variability during dual-task walking. These changes are typically attributed to a more unstable gait behavior . A possible explan- ation for this finding can be derived from learning experi- ments that demonstrated increased muscle activation in children when executing movements on low performance levels. Improving the quality of the movement (i.e., de- velop a less variable and more stable performance) re- duced the amount of muscle activity and co-contractions needed to coordinate the movement properly . On a neural level, low performance during walking (i.e., large variability) might be accompanied by increased muscle co-contractions. Thus, children with lower lean tissue
Figure 1. Experimental procedure. The experiment consisted of a Training followed by a Retrieval session. Sleep group (SG), nighttime-awake group (NA) and daytime-awake group (DA) performed a dualtask (concomitant SRTT and WPAT; upper part). The daytime-awake-subsequent-WPAT group (DAs) performed a single task (SRTT alone then followed by the WPAT; lower part). Training session (left part). SRTT was arranged in blocks (in yellow), for which the trial sequence was fixed, followed by blocks (in green) with random sequences of trials. Numbers in the bottom mark block’s position in the general sequence whereas, numbers on the top indicate the number of trials administered within each block. ‘‘Practice’’ (light blue) indicates the initial practice block, which was not included in the analyses. The WPAT (distractor task) was continuously performed throughout the entire SRTT session. The first and the last fixed sequence blocks (i.e.: block 2 and block 6), followed by the random sequence block 3 and 7, respectively were considered to investigate changes in performance across Training. For clarity, block 2 and block 3 were labeled as ‘‘Training 1’’ whereas block 6 and block 7 were labeled as ‘‘Training 2’’. The difference between mean RTs to random and sequential blocks was the dependent variable being analyzed. Retention interval between training and retrieval sessions (middle part). The sleep group slept the two nights after Training before doing Retrieval in the morning. The nighttime-awake group, instead, stayed awake throughout the first night after Training and slept the second night. The daytime-awake group trained in the morning and was retested in the evening of the same day during which they stayed awake. Retrieval session (right part). Block 9 (fixed trial sequence) and block 10 (random trial sequence) were labeled as Retrieval. The same random minus fixed block difference as in the training session was taken to investigate the RT performance. The task was immediately followed by one bock (in purple) in which a generation task was administered.
The use of integrated measures is especially well suited when speed and accuracy are assumed to be driven by overlapping processes. Task- switching and dual-tasking have been shown to result in performance costs in both speed and accuracy. This indicates that both these per- formance measures rely on the same processes (e.g., Halvorson et al., 2013 ; Han & Marois, 2013 ; Meiran, 1996 ). Apart from response-selec- tion bottleneck models that predict a PRP eﬀect only in the RT (e.g., Pashler, 1994 ), dual-task models, such as the capacity sharing model ( Tombu & Jolicoeur, 2003 ) and the ECTVA model ( Logan & Gordon, 2001 ), can account for SOA eﬀects in RTs and error rates, thus justify- ing the use of integrated measures. Moreover, integrated measures have already been used in the task-switching domain (e.g., Draheim, Hicks, & Engle, 2016 ; Schuch & Pütz, 2018 ) and the dual-task domain ( Han & Marois, 2013 ; Kunde, Pﬁster, & Janczyk, 2012 ).
processing to optimize task switching in terms of reduced switch costs and higher net multitasking efficiency compared to a strictly serial processing manner. A similar effect emerged at least on a descriptive level when comparing the dual-task efficiency of switchers and alternaters in the second experiment. However, neither in the first nor the second experiment the effects of overlapping processing were so strong to actually turn dual-task cost effects in dual-task benefits as would have been reflected in positive ODTPE scores. This was probably due to the fact that in both experiments overlapping processing was only applied in a limited number of trials only and hence could not fully compensate other cost effects. This certainly has prevented a more positive effect of this strategy on overall dual- task efficiency. One reason for this could be a lack of enough practice as needed to fully establish this strategy. Another reason might be the high similarity of the two tasks with respect to the specific processing resources (Wickens, 2002). This might have made task interleaving and overlapping processing particularly difficult and prone to negative side effects. However, it is remarkable that the subgroup of switchers in the second experiment nevertheless were able to realize actual time benefits associated with task switches in up to 47% of switch trials. This shows the potential benefits of a strategy combining task
Lorenza S. Colzato 1 *
1 Institute for Psychological Research, Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands, 2 Department of Psychology, University of Greifswald, Greifswald, Germany
Increasing evidence suggests that cognitive-control processes can be configured to optimize either persistence of information processing (by amplifying competition between decision-making alternatives and top-down biasing of this competition) or flexibility (by dampening competition and biasing). We investigated whether high- frequency binaural beats, an auditory illusion suspected to act as a cognitive enhancer, have an impact on cognitive-control configuration. We hypothesized that binaural beats in the gamma range bias the cognitive-control style toward flexibility, which in turn should increase the crosstalk between tasks in a dual-task paradigm. We replicated earlier findings that the reaction time in the first-performed task is sensitive to the compatibility between the responses in the first and the second task—an indication of crosstalk. As predicted, exposing participants to binaural beats in the gamma range increased this effect as compared to a control condition in which participants were exposed to a continuous tone of 340 Hz. These findings provide converging evidence that the cognitive-control style can be systematically biased by inducing particular internal states; that high-frequency binaural beats bias the control style toward more flexibility; and that different styles are implemented by changing the strength of local competition and top-down bias.
summary and conclusIons
In sum, the present study represents a first step towards understanding the relationship between the cognitive control components involved in task set control by providing evidence that mixing costs and dual-task costs are markers of working memory updating, and that switch costs and switch costs in T2 are indices of the shifting component, but partly also of the updating component. Notably, we also found that the PRP effect correlated substantially (r > .5) with switch costs, suggesting that the PRP effect is related to underlying shifting processes rather than being purely based on passive response queuing processes. The present study also showed that performance costs in multitasking do not meas- ure the components of cognitive control in an isolated and differenti- ated manner. This is in line with the conclusion by Miyake et al. ( 2000 ), who argued that the components of cognitive control are related as well as separable. Future studies need to extend these conclusions to multi- tasking contexts using different types of tasks in order to establish the generality of the present conclusions. In this connection, it would also be important to focus on inhibition and to use bivalent stimuli in order to exclude working memory load as an alternative explanation for the correlation between mixing costs and dual-task costs..
In der Studie von Silsupadol et al. (2009a) zeigte sich ein interessantes Ergebnis. Im Selbstvertrauen, gemessen anhand der ABC-Skala, konnten sich einzig die Teilneh- mer der single-task Gruppe statistisch signifikant verbessern. Dieses Ergebnis ist für die Autorin insofern von Interesse, weil es zeigt, dass Teilnehmer der dual-task Trai- ningsgruppen sich häufig überfordert fühlen und eventuell zu wenig Erfolgserlebnisse verzeichnen können, sodass sie sich unsicherer fühlen als die Teilnehmer der single- task Gruppe. In diesem Fall werden sich diese Personen mit Sicherheit weniger Her- ausforderungen stellen, was somit eine potentielle Gefahr für Immobilität aufzeigt. Dies zeigt, wie enorm wichtig es ist, die Teilnehmer eines Präventionsprogramms nicht zu überfordern und ihnen auch die Möglichkeit zu geben, erfolgreich zu sein, was zum Beispiel durch positives, externes Feedback seitens der Therapeuten zu erreichen ist.
The model has several limitations. First, the increased overall error rate, especially concerning intrusions, is not cov- ered by the model. Second, the model does not show any specific visual behavior during the instruction phase, but only listens to the experimenter. Compared to previous studies that did not use a blank screen during the instruction phase (Halbrügge et al., 2015, 2016), the current data show rela- tively high error rates even in the single-task condition. This suggests that the human participants visually prepared their action sequence while listening to the experimenter in pre- vious studies. More research is needed to elaborate on this point. We are therefore planning to examine the visual pro- cessing of the screen during sequence planning using eye- tracking.
loosing balance and falling. Another approach states that priority of the motor is given over the cognitive task (i.e., “posture first” strategy; Bloem et al., 2006; Yogev-Seligmann et al., 2012 ). Thus, there is no explicit limitation of motor performance during DT practice and the risk of loosing balance and falling is low. Our results are not in line with the first or with the second approach. Task prioritization did not differently favor task performance in the prioritized domain during DT balance performance in young adults. One might again argue that central capacity in healthy young adults is not stressed enough by challenging demands during DT situations. Thus, their cognitive capacity in terms of attentional resources is able to adequately handle both, the motor demand of the stabilometer task as well as the cognitive demand of serial three subtractions. More difficult and attention-demanding tasks during DT conditions might overstrain central capacity in young adults. For example, in older adults it has been shown that particularly visual demands cause greater reductions in DT motor performance compared to other (e.g., verbal or auditive) tasks ( Bock, 2008; Beurskens and Bock, 2012 ). Shumway-Cook et al. proposed that the allocation of attention during the performance of concurrent tasks is complex, depending on many factors including the nature of the cognitive task, the postural task, the goal of the subject, and the instructions, implying that task prioritization is flexible and depends on a variety of individual, task, and environmental factors ( Shumway-Cook et al., 1997; Kelly et al., 2013 ). This finding might be used to explain our results, indicating that the motor and/or cognitive task used itself did not affect prioritization. Consequently, other aspects, such as individual preconditions (e.g., physique, cognitive status and motivation) might affect DT performance following prioritized practice. However, this needs further clarification in terms of DT practice and task prioritization. Further, other studies showed immediate effects of task prioritization during DT conditions ( Schaefer et al., 2008; Kelly et al., 2010; Yogev-Seligmann et al., 2010 ). Our results did not show differences in motor and/or cognitive performance following specific test instructions, indicating that prioritization of one over another task is beneficial during task execution. This however did not lead to a specific learning effect during the retention/transfer phase of the experiment.
Using a dual-task setting, Göthe et al. ( 2016 ) had per- formed a modality-compatibility study with spatial-verbal and spatial-location stimuli in a between-subjects design with bimodal stimulation. They found higher dual-task costs not only for modality-incompatible mappings, but also for location-vocal and verbal-manual mappings of processing code and response, compared to the mappings spatial-manual and verbal-vocal. Notably, the highest costs were observed in the group that faced both an incompatible modality mapping and a location-vocal + verbal-manual fea- ture mapping. In our task-switching setup, all factors were varied within subjects. Note also that none of the mappings in the study by Göthe et al. ( 2016 ) met the narrow defini- tion of ideomotor compatibility (Greenwald, 1972 ), whereas our setup included one ideomotor-compatible condition: the auditory-verbal condition, that is, hearing the word “left” or “right” and responding vocally by saying the same word.
involve cognitive control and attention ( Meyer and Kieras, 1997 ; Logan and Gordon, 2001 ; Luria and Meiran, 2003 ; Koch et al., 2018 ), one should predict a modulation of dual-tasking performance in the near-hand space as compared to far-hand space. Also, societal and technological advances have increased the demands on multimedia multitasking and the complexity of human-technological interactions. The common use of hand- held devices, for example, shifts the visual-manual interaction into a single visuo-spatial region. To date, it remains unclear how the near-hand space affects one’s processing of multiple stimuli in the visual display that are assigned to different tasks. The aim of the present study is to investigate the impact of stimulus-hand proximity in a dual-task situation in which the stimulus (Stimulus 1) of Task 1 is presented on the right and requires responses with the right hand and the stimulus (Stimulus 2) of Task 2 is presented on the left and requires responses with the left hand. We use the psychological refractory period (PRP) paradigm to test the efficiency of the shifting process between Task 1 and Task 2 processing under dual-task conditions. The PRP paradigm allows for an exact assessment of Task 1–Task 2 shifts due to the precise experimental manipulation of the temporal overlap of two tasks. The better Task 2 performance at short SOAs (i.e., indexed by the size of the PRP effect), the more efficient the engagement of Task 2 processing. The PRP paradigm thus represents a perfectly suitable approach to precisely measure the shifting operation in dual-task contexts.
The dual labor market theory allows the analysis of various issues. For example, barriers to satisfying the structural labor demand by women and teenagers, availability of unstable and low productivity jobs in advanced economies, employment of immigrants in jobs not attractive to local workers, barriers to promote the unattractive jobs by market mechanisms such as raising wages, and acceptance of unattractive jobs by vulnerable social groups (Kogan 2007).
the memory-bias account because the amount of prior experience of a focal task seems to matter when it comes to underestimating task duration ( Roy and Christenfeld, 2007 ). Moreover, prediction bias is reduced when feedback about previous task duration is provided, thus correcting memory ( Roy et al., 2008 ). Similar to research supporting the inside–outside account ( Buehler et al., 1994 ), Roy et al.’s (2008) findings suggest that using previous task information can reduce prediction bias, suggesting some complementarity between the memory-bias and inside–outside accounts. However, Roy et al. (2008) found that such information had to be accurate to be beneficial whereas this was not examined by Buehler et al. (1994) , suggesting an arguably subtle difference between the two accounts. A more obvious way in which the accounts differ though is in the link between the use of previous task information and prediction bias, with the inside–outside account predicting that bias is due to not using information and the memory-bias account predicting that bias occurs because such information is incorrectly used.
13 schnellen Ursachendiagnostik im Bereich der Akutmedizin bei Thoraxschmerz- Patienten zu Gute kommt. Der Dual Energy Modus, in welchem die Röntgenquellen mit unterschiedlichen Energien betrieben werden, erlaubt eine Materialdifferenzierung, was eine Unterscheidung von beispielsweise Knochen, Jod oder anderen organischen Materialien ermöglicht. [6-17] Dass diese technischen Neuerungen einen weiteren wertvollen Beitrag zur klinischen Diagnostik leisten können, steht angesichts der vielfältigen Einsatzmöglichkeiten außer Frage. Es galt jedoch nachzuweisen, dass diese neuen Verfahren nicht zu einer zusätzlichen Strahlenbelastung im Vergleich zu den bisher verwendeten Methoden zu Lasten der untersuchten Patienten führen. Durch die Verwendung eines anthropomorphen Phantoms und geeigneter Detektoren konnten die resultierenden Strahlenbelastungen der unterschiedlichen Untersuchungsprotokolle auf den menschlichen Organismus quantifiziert werden. Für die Durchführung der Dual Energy Protokolle konnte im Vergleich zu den standardmäßigen Computertomographie-Untersuchungen eine Dosisneutralität bei vergleichbarer Bildqualität und deutlich verbessertem Kontrast-zu-Rausch Verhältnis nachgewiesen werden. Das Dual Energy Protokoll kommt heute unter anderem routinemäßig bei Patienten mit klinischem Verdacht auf eine Pulmonalarterien-Embolie zur Anwendung.
Wenn wir Unterrichtsaufzeichnungen im Hinblick auf den Einsatz von Lernaufgaben analysieren, dann tun wir eigentlich nichts Neues. Denn der Dreischritt von Planung, Realisation und Reflexion des Unterrichts ist wohl bekannt. Neu ist die Fokussierung auf die Variable „Aufgabe“. Lechner hat 2007 nachdrücklich auf die Aufgabe als zentrale Planungsvariable hingewiesen (vgl. Lechner 2007, S. 127). Gleichwohl ist die Aufgabe kein Selbstweck, sondern hat als Lern- oder Leistungsaufgabe eine be- stimmte Funktion zu erfüllen. Die Aufgabe soll funktionieren, also in erster Linie inhalt- lich valide sein. Sie muss bewirken, was sie bewirken soll – und nicht etwas anderes. Zugleich soll sie für (den einzelnen) Lerner optimalen Lernfortschritt ermöglichen. Die Unterscheidung von task as workplan und task in process geht auf Legutke (vgl. Legutke 2006, S. 140-148) zurück, der das Konzept aufgabenbasierten Lernens im Fremdsprachenunterricht etabliert hat – und zwar vor allem in Abgrenzung zu „stark gelenkten, kleinschrittigen und in erster Linie formorientierten Aufgaben“ (Hu 2006, S. 84). Die Lerner werden als verantwortliche Subjekte im Handlungsraum
The experimental setup is based on the same physical principle as the dual comb realization in the previous chapter. Here, two ytterbium lasers were implemented that are emitting at 1040 nm. Besides the important extension of an enhancement cavity instead of a single- pass cell for an improved sensitivity, an ytterbium (Yb) amplifier was also installed after one of the two fs lasers (see figure 4.1). The first frequency comb is amplified and injected into the enhancement cavity located in a gas chamber. As already noted in the previous chapter, it is preferable to have a balanced beating signal for a large signal-to-noise ratio of the interferogram. Since the high finesse cavity consists of high reflecting mirrors, the light that is transmitted by one of these mirrors and that is used as one of the two contributions for the beating signal will be of little power. The integrated Yb fiber amplifier in the setup helps to get to a more balanced signal since it increases the power of the light coupled into and out of the cavity. The light that is transmitted by the cavity and that carries the absorption information is overlapped with the output of a second frequency comb that has a slightly different repetition rate. The beating signal of the two combs which is located in the radio frequency domain is sent onto a fast photodiode. The signal is low-pass filtered and transferred to a data acquisition board on a computer for digitization and Fourier transformation of the data in order to reveal the absorption spectrum.