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part of action preparation is deciding what the relevant task is. This task-decision process is conceptually separate from response selection. To show this, the authors manipulated task conflict in a spatial task-switching paradigm, using conflict stimuli that appeared during trials with univalent targets (affording 1 task). The conflict stimuli afforded task identity because they were used as task cues with bivalent targets (affording 2 tasks) that were intermixed with the univalent targets. Thus, for univalent targets, irrelevant stimuli either caused low task conflict or high task conflict. In three experiments, the authors found poorer performance in high task conflict trials than in low task conflict trials. Task conflict was introduced during target appearance (Experiment 1) or task preparation (Experiments 2 and 3). In the latter case, the task conflict effect decreased with increasing task preparation time showing that task preparation involves task decision. [ABSTRACT FROM AUTHOR]

In this study, we investigated picture (Experiments 1 and 2) and word (Experiments 3 and 4) processing using different tasks. In Experiments 1 and 3, easy and difficult conditional naming tasks were compared to a free naming task. In Experiments 2 and 4, easy and difficult conditional naming tasks were compared to easy and difficult manual forced-choice semantic decision tasks. For pictures, we showed that a difficult semantic categorization determined a cost for the conditional naming with respect to the free naming (Experiment 1). Also, we found that the difference in RTs between the easy and difficult conditional naming tasks was much smaller than the difference between the easy and difficult forced-choice semantic decision tasks (Experiment 2). For words, results showed that free reading was faster than easy conditional reading, which in turn was faster than difficult conditional reading (Experiment 3). An analogous pattern of results was obtained when the easy and difficult conditional reading tasks were compared to the easy and difficult forced-choice semantic decision tasks (Experiment 4). Globally, the results showed that whether a cost is observed or not depends upon the relative timing of the classification and name retrieval processes. A theoretical framework has been proposed. [ABSTRACT FROM AUTHOR]

The idea that observing an action triggers an automatic and obligatory activation of an imitative action in the motor system of the observer has recently been questioned by studies examining complementary actions. Instead of a tendency for imitation, cooperative settings may facilitate the execution of dissimilar actions, resulting in a relative disadvantage for imitative actions. The present study aimed at clarifying the contribution of associative learning and interference of task representations to the reversal of congruency effects. To distinguish between the two, an experiment was designed, in which we increased the effects of associative learning and minimized the effects of task interference. Participants completed a series of imitation and complementary action runs, in which they continuously imitated or complemented the actions of a virtual co-actor. Each run was alternated with a test run showing the same actions but including color-cues, and the participants were instructed to respond to color instead of the actor’s posture. Reaction times to test runs showed no reversal of facilitation effects between the imitation and complementary action conditions. This result strongly argues that associative learning cannot adequately account for reversed facilitation effects. Our study provides additional support for action–perception models that allow flexible selection of action–perception coupling and challenges the existing models purely based on stimulus–response associations. [ABSTRACT FROM AUTHOR]

In task switching experiments participants have to respond to the same set of stimuli while task instructions vary (e.g., digit stimuli are assigned to left- or right-sided key presses by means of magnitude vs. parity classification). Response congruency effects denote worse performance for a stimulus, which is associated with different responses in the two tasks as compared to a stimulus, which is associated with the same response. Previous research suggests that such effects reflect direct links between stimuli and responses acquired in the course of experimental practice. In the current study we investigated the impact of stimulus-specific practice and task instruction by reversing the S–R mapping of one task (Experiment 1) or replacing one task with a new one (Experiment 2) in the second half of an experimental session. Consistent with the direct link account, S–R links practiced during the first half of the experiment largely determined congruency effects despite altered task instructions. Furthermore, the results suggest that previously practiced S–R links (a) can be relatively quickly overwritten by practicing a novel S–R mapping, and (b) are subject to passive decay when no longer in use. [ABSTRACT FROM AUTHOR]

In a running memory span task, the participants are presented with a list of items (e.g. numbers or words) of an unknown length, because this length varies from trial to trial. In one variation of the procedure the participants must report a certain fixed number of items (e.g. four) from the end of the list. According to Morris and Jones ( British Journal of Psychology, 81, 111–121, ), the recalled items must be updated in memory as the presentation of the list progresses. Ruiz, Elosúa and Lechuga ( The Quarterly Journal of Experimental Psychology, 5, 887–905, ) noted that an active strategy implies an inhibition in memory of the final discarded items, and did not find results which supported this hypothesis. The aim of this study is to check whether or not participants adopt an active processing strategy in extreme conditions. Experiment 1 uses catch trials, which induce the participants not to discard the first items of the lists, and also short lists (of 4, 7, 8, 9 and 10 items); these could be considered optimal conditions for updating. However, it should also be pointed out that with an upper limit of 10 items per list, participants could try to memorise the whole list in most of the trials. One way to discourage this strategy is including lists well over span (e.g. 14–26 items). The purpose of Experiment 2 was to analyse the 10-item lists in two conditions: within a context of much longer lists (well over span) in most of the trials and within a context of shorter lists (data of Experiment 1). Results in both experiments, from the analysis of location errors, indicate that even in these conditions the participants do not seem to carry out the supposed active updating of the memory set. [ABSTRACT FROM AUTHOR]

Responses are faster when the side of stimulus and response correspond than when they do not correspond, even if stimulus location is irrelevant to the task at hand: the correspondence, spatial compatibility effect, or Simon effect. Generally, it is assumed that an automatically generated spatial code is responsible for this effect, but the precise mechanism underlying the formation of this code is still under dispute. Two major alternatives have been proposed: the referential-coding account, which can be subdivided into a static version and an attention-centered version, and the attention-shift account. These accounts hold clear-cut predictions for attentional cuing experiments. The former would assume a Simon effect irrespective of attentional cuing in its static version, whereas the attention-centered version of the referential-coding account and the attention-shift account would predict a decreased Simon effect on validly as opposed to invalidly cued trials. However, results from previous studies are equivocal to the effects of attentional cuing on the Simon effect. We argue here that attentional cueing reliably modulates the Simon effect if some crucial experimental conditions, mostly relevant for optimizing attentional allocation, are met. Furthermore, we propose that the Simon effect may be better understood within the perspective of supra-modal spatial attention, thereby providing an explanation for observed discrepancies in the literature. [ABSTRACT FROM AUTHOR]

Often the performance of a task does not only require the processing of certain stimuli in certain ways, but also certain patterns of interlimb coordination. We studied shifts between different tasks involving different patterns of intermanual coupling by means of the timed-response procedure, which allows to trace state variables related to task sets. The tasks required the production of rapid bimanual reversal movements with symmetric or parallel directions. Symmetric movements are associated with symmetric coupling, as indicated by positive intermanual correlations between the directions of left-hand and right-hand movements, whereas parallel movements are associated with parallel coupling, as indicated by negative intermanual correlations. Task switches were associated with gradual changes of the intermanual correlations, which indicate the state of intermanual coupling as a major ingredient of a task set, in the course of action preparation. At short preparation intervals intermanual correlations were those appropriate for the preceding trial; with increasing preparation time they were replaced by those appropriate for the current trial, but the influence of the preceding trial did not disappear completely. In-between trials, intermanual coupling drifted toward a symmetric coupling, but not to uncoupled limbs. After a change of the task the specification of movement directions was slowed, but its initiation was not delayed. According to these results, task sets relax toward attractors which can be different from the absence of task sets. They are gradually configured during task preparation with a persistent influence of the preceding task, and the specification of response characteristics does not wait until the configuration of the new task set is completed. [ABSTRACT FROM AUTHOR]

Switch costs occur whenever participants are asked to switch between two or more task sets. In a typical task switching experiment, participants have to switch between two task sets composed of up to four different stimuli per task set. These 2 (task sets) × 4 (stimuli) contain only 8 different stimulus–response (S–R) mappings, and the question is why participants base their task performance on task sets instead of S–R mappings. The current experiments compared task performance based on task rules with performance based on single stimulus–response mappings. Participants were led to learn eight different S–R mappings with or without foreknowledge about two underlying task sets. Without task set information no difference between shifts and repetitions occurred, whereas introducing task sets at the beginning led to significant switch costs. Most importantly, introducing task sets in the middle of the experiment also resulted in significant switch costs. Furthermore, introducing task rules at the beginning of the experiment lead to slower RTs when simple stimuli (Experiment 1) had to be processed. This detrimental effect disappeared with more complex stimuli (Experiment 2). Results will be discussed with respect to cognitive control. [ABSTRACT FROM AUTHOR]

Recent findings indicate that two distinct mechanisms can contribute to a Simon effect: a visuomotor information transmission on the one hand and a cognitive code interference on the other hand (see for e.g., Wiegand & Wascher, in Journal of Experimental Psychology: Human Perception and Performance ). Furthermore, it was proposed that the occurrence of one or the other mechanism strongly depends on the way responses are coded. Visuomotor information transmission seems to depend on a correspondence between stimulus position and spatial anatomical status of the effector, whereas cognitive code interference is thought to be based on relative response location codes. To further test the spatial anatomic coding hypothesis, three experiments were conducted, in which the Simon effect with unimanual responses was investigated for horizontal (Experiment 1 and 2) and vertical (Experiment 3) stimulus–response (S–R) relations. Based on the finding of a decreasing effect function (indicating the presence of visuomotor information transmission) for horizontal and vertical S–R relations, it was concluded that visuomotor information transmission occurs whenever there is an overlap between the spatial stimulus feature and parameters of the motor representation of the response. Furthermore, the specific motor representation seems to be task dependent, that is, it entails those response parameters that clearly differentiate between the two response alternatives in a given task situation. [ABSTRACT FROM AUTHOR]

In the explicit cuing version of the task-switching paradigm, each individual task is indicated by a unique task cue. Consequently, a task switch is accompanied by a cue switch. Recently, it has been proposed that priming of cue encoding contributes to the empirically observed switch costs. This proposal was experimentally supported by using a 2:1 mapping of cues to tasks, so that a cue switch does not necessarily imply a task switch. The results indeed suggested a substantial contribution of “cue-switch costs” to task-switch costs. Here we argue that the 2:1 mapping potentially leads to an underestimation of “pure” task-switch costs. To support this argument, we report the results of a new study in which we used “transition cues” that indicate the identity of the current task based on the identity of the preceding task. This new type of cue allows a full factorial manipulation of cue switches and task switches because it includes the condition in which a cue repetition can also indicate a task switch (i.e., when the “switch” cue is repeated). We discuss the methodological implications and argue that the present approach has merits relative to the previously used 2:1 mapping of cues to tasks. [ABSTRACT FROM AUTHOR]

When people frequently alternate between simple cognitive tasks, performance on stimuli which are assigned the same response in both tasks is typically faster and more accurate than on stimuli which require different responses for both tasks, thus indicating stimulus processing according to the stimulus–response (S–R) rules of the currently irrelevant task. It is currently under debate whether such response congruency effects are mediated by the activation of an abstract representation of the irrelevant task in working memory or by “direct” associations between specific stimuli and responses. We contrasted these views by manipulating concurrent memory load (Experiment 1) and the frequency of specific S–R associations (Experiment 2). While between-task response congruency effects were not affected by the amount of concurrent memory load, they were much stronger for stimuli that were processed frequently in the context of a competitor task. These findings are consistent with the idea that a large portion of the congruency effects stems from direct S–R associations and they do not support a sole mediation by task-set activation in working memory. [ABSTRACT FROM AUTHOR]

In four experiments we investigated whether incidental task sequence learning occurs when no instructional task cues are available (i.e. with univalent stimuli). We manipulated task sequence by presenting three simple binary-choice tasks (colour, form or letter case decisions) in regular repeated or random order. Participants were required to use the same two response keys for each of the tasks. We manipulated response sequence by ordering the stimuli so as to produce either a regular or a random order of left versus right-hand key presses. When sequencing in both, or either, separate stream (i.e. task sequence and/or response sequence) was changed to random, only those participants who had processed both sequences together showed evidence of sequence learning in terms of significant response time disruption (Experiments 1–3). This effect disappeared when the sequences were uncorrelated (Experiment 4). The results indicate that only the correlated integration of task sequence and response sequence produced a reliable incidental learning effect. As this effect depends on the predictable ordering of stimulus categories, it suggests that task sequence learning is perceptual rather than conceptual in nature. [ABSTRACT FROM AUTHOR]

We adopted the Psychological Refractoriness Paradigm to study whether perceptual Goodness affects the load of central processing resources. In three dual-task experiments, 2-Alternative Forced Choice auditory classification was followed by a same–different task in which Garner’s classical five-dot patterns were presented. Goodness of these patterns and stimulus-onset asynchrony (SOA) between the first and second task were varied between trials. These factors had additive effects on response latencies and accuracy, indicating that pattern Goodness determines central processing load in performing the same–different task. In a fourth experiment, same–different judgment with Garner patterns was the single task. SOA between the first and second pattern was varied. Over-additive effects of Goodness with decreasing SOA were obtained, indicating sharing of central resources between consolidation of the first Garner pattern and performing the same–different task. Whereas, the resources needed for the latter, again, depend on Goodness, those needed for consolidation are independent of it. [ABSTRACT FROM AUTHOR]

A crucial demand in dual tasks suffering from a capacity limited processing mechanism is task-order scheduling, i.e. the control of the order in which the two component tasks are processed by this limited processing mechanism. The present study aims to test whether the lateral prefrontal cortex (LPFC) is associated with this demand. For this, 15 participants performed a psychological refractory paradigm (PRP) type dual task in an event-related functional magnetic resonance (fMRI) experiment. In detail, two choice reaction tasks, a visual (response with right hand) and an auditory (response with left hand), were presented with a temporal offset of 200 ms, while the participants were required to respond to the tasks in the order of their presentation. Importantly, the presentation order of the tasks changed randomly. Based on previous evidence, we argue that trials in which the present task order changed as compared to the previous trial (different-order trials) impose higher demands on task coordination than same-order trials do. The analyses showed that cortical areas along the posterior part of the left inferior frontal sulcus as well as the right posterior middle frontal gyrus were more strongly activated in different-order than in same-order trials, thus supporting the conclusion that one function of the LPFC for dual-task performance is the temporal coordination of two tasks. Furthermore, it is discussed that the present findings favour the active scheduling over the passive queuing hypothesis of dual-task processing. [ABSTRACT FROM AUTHOR]

Recent fMRI studies suggest that the inferior frontal sulcus (IFS) is involved in the coordination of interfering processes in dual-task situations. The present study aims to further specify this assumption by investigating whether the compatibility between stimulus and response modalities modulates dual-task-related activity along the IFS. It has been shown behaviorally that the degree of interference, as measured by dual-task costs, increases in modality-incompatible conditions (e.g. visual–vocal tasks combined with auditory–manual tasks) as compared to modality-compatible conditions (e.g. visual–manual tasks combined with auditory–vocal tasks). Using fMRI, we measured IFS activity when participants performed modality-compatible and modality-incompatible single and dual tasks. Behaviorally, we replicated the finding of higher dual-task costs for modality-incompatible tasks compared to modality-compatible tasks. The fMRI data revealed higher activity along the IFS in modality-incompatible dual tasks compared with modality-compatible dual tasks when inter-individual variability in functional brain organization is taken into account. We argue that in addition to temporal order coordination (Szameitat et al., 2002), the IFS is involved in the coordination of cognitive processes associated with the concurrent mapping of sensory information onto corresponding motor responses in dual-task situations. [ABSTRACT FROM AUTHOR]

Practice can dramatically reduce dual-task interference, but typically does not eliminate interference entirely. Residual interference after practice is especially large with certain non-preferred modality pairings (e.g., auditory–manual and visual–vocal). Does this residual interference imply the existence of a persistent central-processing bottleneck? To address this question, we transferred participants with previous dual-task practice to a psychological refractory period design. Although we observed residual dual-task costs in all four experiments, there was no evidence for a bottleneck, even with non-preferred modality pairings. We conclude that practice can eliminate the bottleneck limitation, but performance is still subject to other sources of interference, such as competition between central codes of the two tasks. [ABSTRACT FROM AUTHOR]

This study deals with the problem of whether the processing of irrelevant location information in Simon-like tasks is triggered exogenously or endogenously. In Experiment 1, the primary task required one to press, as fast as possible, a left-hand-side key or a right-hand-side key (R1) to the pitch of a tone that was presented binaurally (S1). The secondary task required identifying, without time constraints, a visual stimulus (S2) that appeared randomly to the left or right of screen center. Results showed that there was a correspondence (i.e., a cross-task Simon effect) between the location of R1 and the location of S2 when S2 was presented alone. The cross-task Simon effect became much smaller (and in-significant) when a noise stimulus was presented contralateral to S2. Experiment 2 was similar to Experiment 1, except that S2 appeared unpredictably in only one-third of the trials. Results of Experiment 2 closely replicated those of Experiment 1: the cross-task Simon effect was much greater when S2 was presented alone. Experiment 3 differed from Experiment 1 because S2 had to be processed in only one-third of the trials, in which its identity was to be reported. In the remaining two-thirds of the trials, participants could ignore S2. Results confirmed that the cross-task Simon effect was much greater when S2 was presented alone. In contrast, it did not matter whether S2 had to be processed or not. In conclusion, the present study supports the hypothesis that the task-irrelevant spatial code of the stimulus is formed automatically, likely through an exogenously triggered selection. The role of endogenously initiated selection, if any, is much less important. [ABSTRACT FROM AUTHOR]

We investigated if task switching affects late response processes that occur after the selection of a response. Subjects performed a sequence of two responses. The first and second response were selected, and then executed in close succession. The interresponse interval (IRI) was taken as a measure of late response processes. The two responses could either belong to different tasks (task-switch condition), or to the same task that was performed twice (task-repetition condition). In all three experiments, the IRI was found to be longer in the task-switch condition than in the task-repetition condition, consistent with the idea that task switching affected late response processes. However, the effects of the manipulation of the stimulus-onset asynchrony revealed that the tendency to perform the two responses as a sequence was reduced in the task-switch condition relative to the task-repetition condition. Thus, the data do not provide unequivocal evidence for task switching affecting late response processes. The data show, however, that task switching affected action sequencing. Two actions that do not belong to the same task context are less likely to be performed as an action sequence. We suggest that task switching interacts with higher-order control processes that cannot be studied within the traditional task-switching paradigm. [ABSTRACT FROM AUTHOR]

A number of recent studies casts doubt on the empirical separability of processes of task preparation from the actual execution of the respective task. We report two experiments in which we separated the precueing of a task from its execution by an intervening task. In addition, for the precued task we employed imperative stimuli that in most cases were associated with a competing task, making the execution of this task dependent on an internal representation of the information provided by the precue. Under these conditions, the performance of the intervening task suffered specific interference as a function of its relation to the precued task. This suggests that the encoding of the precue resulted in specific preparation for the precued task. Furthermore, the transition between the intervening task and the precued task was associated with relatively small costs that did not vary as a function of the interval that separated the two tasks. This also suggests that a great deal of preparation for the second task already took place during the encoding of the precue. Further observations suggest that the resolution of the interference between a memory-based task representation, as well as a perceptually induced task representation, and the representation of the currently relevant task took place on the level of individual task features. [ABSTRACT FROM AUTHOR]

The present study assessed three hypotheses of how practice reduces dual-task interference: Practice teaches participants to efficiently integrate performance of a task pair; practice promotes automatization of individual tasks, allowing the central bottleneck to be bypassed; practice leaves the bottleneck intact but shorter in duration. These hypotheses were tested in two transfer-of-training experiments. Participants received one of three training types (Task 1 only, or Task 2 only, or dual-task), followed by dual-task test sessions. Practice effects in Experiment 1 (Task 1: auditory–vocal; Task 2: visual–manual) were fully explained by the intact bottleneck hypothesis, without task integration or automatization. This hypothesis also accounted well for the majority of participants when the task order was reversed (Experiment 2). In this case, however, there were multiple indicators that several participants had succeeded in eliminating the bottleneck by automatizing one or both tasks. Neither experiment provided any evidence that practice promotes efficient task integration. [ABSTRACT FROM AUTHOR]

Two experiments with 72 participants in total investigated the route-angularity effect. This effect is shown when a greater number of turns along a route increase the estimated length of this route. In this study it was shown that the route-angularity effect is likely to be a memory-based effect depending on task difficulty. The important factor seems to be how heavily memory is loaded during learning. The route-angularity effect even appears in intentional learning, when memory is loaded heavily. Under this learning condition participants know beforehand that they have to estimate distances. All experiments were conducted in a controlled virtual environment, which allows a reliable investigation of distance estimations in environmental space. [ABSTRACT FROM AUTHOR]

Serial position effects in implicit and explicit memory were investigated in a short-term memory task. A study list composed of four, spatially distributed, two-digit numbers was presented, followed by an item recognition task (explicit test) and an implicit memory task in which participants were asked to verify a simple addition equation where the presented answer was either primed or not primed by one of the number pairs in the study list. Similar serial position effects were observed in explicit and implicit memory, with faster response times for correct decisions on the first than on the later list positions. The presence of a primacy effect but no recency effect is consistent with previous studies of explicit memory with visual presentation. The results suggest that similar principles of temporal information processing govern priming and episodic short-term memory. [ABSTRACT FROM AUTHOR]

In two experiments with the serial reaction-time task, participants were presented with deterministic or probabilistic sequences under single- or dual-task conditions. Experiment 1 showed that learning of a probabilistic structure was not impaired over a first session by performing a counting task, but that such an interference arose over a second session, when the knowledge was tested under single-task conditions. In contrast, the effects of the secondary task arose earlier for participants exposed to deterministic sequences. This difference between deterministic and probabilistic sequences disappeared in Experiment 2, where the counting task was performed on tones associated to the locations. Comparisons between sessions indicated that the secondary task affected not only the expression but also the acquisition of sequence learning, and that greater interference was observed in those conditions that yielded more explicit knowledge. These results suggest that the effects of a dual task on the measures of implicit sequence learning may be partly due to the intrusion of explicit knowledge and partly due to the disruption of the sequence produced by the inclusion of random events. [ABSTRACT FROM AUTHOR]

The present work investigated the right-left prevalence effect caused by the automatic activation of horizontal and vertical spatial codes in a task (Simon task) in which spatial information is task-irrelevant. Experiment 1 showed a horizontal Simon effect and a vertical Simon effect with a two-dimensional stimulus-response set. In Experiments 2 and 3, the right-left prevalence was obtained in two-dimensional Simon tasks with two contralateral effectors and four effectors respectively. Experiment 4 showed that horizontal coding is based on multiple spatial codes, whereas only one spatial code was formed for vertical coding. On the whole, these results support the notion that the right-left prevalence effect is a general phenomenon affecting spatial coding, and suggest that the horizontal dimension is prevalent because it is based on multiple spatial codes. [ABSTRACT FROM AUTHOR]