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Iring Koch

Publications and source records attributed to Iring Koch.

At least 19 recordsLinked to original sources
PubMed2006

Methodological and empirical issues when dissociating cue-related from task-related processes in the explicit task-cuing procedure.

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.

Adult↗
PubMed2006

Chunking in task sequences modulates task inhibition.

In a study of the formation of representations of task sequences and its influence on task inhibition, participants first performed tasks in a predictable sequence (e.g., ABACBC) and then performed the tasks in a random sequence. Half of the participants were explicitly instructed about the predictable sequence, whereas the other participants did not receive these instructions. Task-sequence learning was inferred from shorter reaction times (RTs) in predictable relative to random sequences. Persisting inhibition of competing tasks was indicated by increased RTs in n- 2 task repetitions (e.g., ABA) compared with n- 2 nonrepetitions (e.g., CBA). The results show task-sequence learning for both groups. However, task inhibition was reduced in predictable relative to random sequences among instructed-learning participants who formed an explicit representation of the task sequence, whereas sequence learning and task inhibition were independent in the noninstructed group. We hypothesize that the explicit instructions led to chunking of the task sequence, and that n- 2 repetitions served as chunk points (ABA-CBC), so that within-chunk facilitation modulated the inhibition effect.

Adult↗
PubMed2006

Voluntary selection of task sets revealed by functional magnetic resonance imaging.

In everyday life, we have to selectively adapt our behavior to different situations and tasks. In cognitive psychology, such adaptive behavior can be investigated with the task-switching paradigm. However, in contrast to everyday life, in experiments participants are unequivocally told which task to perform. The present functional magnetic resonance imaging (fMRI) study was set out to investigate processes that are relevant when participants can decide by their own which task to perform. The number of tasks to choose from was varied between a forced condition (no choice) and two voluntary selection conditions (two or three choices). We expected to find prolonged reaction times as well as higher activations within the midcingulate cortex for the choice conditions compared to the no-choice condition. The fMRI results revealed a significant activation difference for the choice conditions versus the no-choice condition. For the choice contrast, activation was found in the rostral cingulate zone (RCZ) as well as the superior parietal lobule and the posterior part of the intraparietal sulcus. These activations revealed no selection-specific difference between three and two choices. Finally, a post hoc analysis showed that the activation in the RCZ is not associated with higher task-dependent response conflict when participants can select a task set. Taken together, these findings indicate that distinct brain areas are involved in the voluntary selection of abstract task set information.

Adult↗
PubMed2006

Cue-based preparation and stimulus-based priming of tasks in task switching.

In this study, we investigated the interaction of three different sources of task activation in precued task switching. We distinguished (1) intentional, cue-based task activation from two other, involuntary sources of activation: (2) persisting activation from the preceding task and (3) stimulus-based task activation elicited by the task stimulus itself. We assumed that cue-based task activation increases as a function of cue-stimulus interval (CSI) and that task activation from the preceding trial decays as a function of response-stimulus interval Stimulus-based task activation is thought to be due to involuntary retrieval of stimulus-associated tasks. We manipulated stimulus-based task activation by mapping each of the stimuli consistently to only one or the other of the two tasks. After practice, we reversed this mapping in order to test the effects of item-specific stimulus-task association. The mapping reversal resulted in increased reaction times and increased task shift costs. These stimulus-based priming effects were markedly reduced with a long CSI, relative to a short CSI, suggesting that stimulus-based priming shows up in performance principally when competition between tasks is high and that cue-based task activation reduces task competition. In contrast, lengthening the response-cue interval (decay time) reduced shift costs but did not reduce the stimulus-based priming effect The data are consistent with separable stimulus-related and response-related components of task activation. Further theoretical implications of these findings are discussed.

Adult↗
PubMed2005

Task switching and action sequencing.

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.

Adult↗
PubMed2005

Effects of switching between leftward and rightward pro- and antisaccades.

Previous studies suggested that random switching between pro- and antisaccades increases errors in both tasks. However, little is known about the effects of switching between leftward and rightward saccades (response switching). The present study investigated task and response switching using an alternating runs procedure. Tasks (i.e., prosaccades versus antisaccades) were switched every second trial. Response switches (i.e., leftward saccades versus rightward saccades) were counterbalanced across tasks and task-switching conditions. Task switching increased errors in both tasks. Response switching increased errors when antisaccades were preceded by antisaccades but not when antisaccades were preceded by prosaccades or for prosaccades regardless of the preceding saccade type. The task-switch effects suggest that both pro- and antisaccade trials activate specific production rules that can persist in a subsequent trial. The differential response-switch effects may reflect different modes of response activation in pro- and antisaccades (sensorimotor transformation of visual information versus selection of motor programs).

Adolescent↗
PubMed2005

Task-set inertia and memory-consolidation bottleneck in dual tasks.

Three dual-task experiments examined the influence of processing a briefly presented visual object for deferred verbal report on performance in an unrelated auditory-manual reaction time (RT) task. RT was increased at short stimulus-onset asynchronies (SOAs) relative to long SOAs, showing that memory consolidation processes can produce a functional processing bottleneck in dual-task performance. In addition, the experiments manipulated the spatial compatibility of the orientation of the visual object and the side of the speeded manual response. This cross-task compatibility produced relative RT benefits only when the instruction for the visual task emphasized overlap at the level of response codes across the task sets (Experiment 1). However, once the effective task set was in place, it continued to produce cross-task compatibility effects even in single-task situations ("ignore" trials in Experiment 2) and when instructions for the visual task did not explicitly require spatial coding of object orientation (Experiment 3). Taken together, the data suggest a considerable degree of task-set inertia in dual-task performance, which is also reinforced by finding costs of switching task sequences (e.g., AC --> BC vs. BC --> BC) in Experiment 3.

Attention↗
PubMed2005

Advance preparation and stimulus-induced interference in cued task switching: further insights from BOLD fMRI.

To switch from one cognitive task to another is thought to rely on additional control effort being indicated by performance costs relative to repeating the same task. This switch cost can be reduced by advance task preparation. In the present experiment the nature of advance preparation was investigated by comparing a situation where an explicit task cue was presented 2000 ms in advance of the target stimulus (CTI-2000) with a situation where cue and target were presented in close succession (CTI-100). We mapped the blood-oxygenation-level-dependent (BOLD) activation correlates of switch-related control effort and advance task preparation to test alternative explanations why advance preparation is reducing switch costs. A previously reported control-related cortical network of frontal and parietal brain areas emerged that was more strongly activated for switching between tasks. However, this was true exclusively for CTI-100 where no advance task preparation was possible. At CTI-2000 these same brain areas were equally engaged in both switch and repeat trials. For some of these areas, this common activation was time-locked to the presentation of both the cue as well as the target. Other areas were exclusively associated with target processing. The overall pattern of results suggests that advance task preparation is a common process of pre-activating (cue-locked activation) the currently relevant task set which does not face interference from a persisting N - 1 task set. During target processing the same brain areas are re-engaged (subsequent target-locked activation) to apply the pre-activated task set. Though being common to repeat and switch trials, advance preparation has a differential benefit for switch trials. This is because the instructed task set has time to settle into a stable state, thus becoming resistant against disruption from the previous task set, which is retrieved by the current target stimulus.

Adult↗
PubMed2005

Internally generated and directly cued task sets: an investigation with fMRI.

It is widely acknowledged that the prefrontal cortex (PFC) plays a major role for goal-directed behaviour. In this context it is usually necessary to coordinate environmental information and internally represented intentions. Such goal-directed "endogenous control processes" can be investigated with the task-switching paradigm in which participants are required to alternate between different tasks. In the present study, we aimed at investigating different degrees of endogenous control by introducing two cue types with varying directness of the cue-task association. The "transition cues" informed the participants about repeating or switching the task but not about the task identity. Contrary to that, the "task cues" were directly associated with the upcoming task set. Since the transition cues are not directly associated with the task set they should require a higher demand of endogenous control than the task cues. The comparison of both cue types revealed frontolateral as well as frontomedian activations for the transition cue. We assume that the frontolateral activation reflects the coordination of information within working memory (WM) and the frontomedian cortex reflects the higher demand for endogenous control. Furthermore, regions of interest (ROIs) analyses indicate an important role for anterior regions along the left inferior frontal sulcus and frontomedian wall. This is suggested to reflect a functional gradient in anterior-posterior direction which is linked to the relative degree of required endogenous control.

Adult↗
PubMed2005

Switching of response modalities.

When participants perform a sequence of different tasks, it is assumed that the engagement in one task leads to the inhibition of the previous task. This inhibition persists and impairs performance when participants switch back to this (still inhibited) task after only one intermediate trial. Previous task-switching studies on this issue have defined different tasks at the level of stimulus categorization. In our experiments we used different response modalities to define tasks. Participants always used the same stimulus categorization (e.g., categorize a digit as odd vs. even), but had to give a vocal, finger, or foot response (A, B, or C). Our results showed a higher reaction time and error rate in ABA sequences than in CBA sequences, indicating n - 2 repetition cost as a marker for persisting task inhibition. We assume that different response modalities can define a task and are inhibited in a "task switch" in the same way as stimulus categories are inhibited.

Adult↗
PubMed2005

Response preparation and code overlap in dual tasks.

In a dual-task paradigm, a visual-encoding task with a deferred verbal report of a moving target was combined with a speeded task, in which participants prepared a precued leftward or rightward key-press response that was withheld until an auditory go signal. We manipulated the interval between the response cue and the target for the visual-encoding task, the interval between this target and the go signal, and spatial cross-task compatibility between the direction of the target movement in the visual task and the speeded manual response. The results of two experiments suggest that visual encoding interferes with response preparation and with the initiation of the prepared manual response at a short target-go interval. Also, responses were faster in compatible than in incompatible trials, indicating a cross-task compatibility effect. Experiment 2 reversed this compatibility effect by instruction, suggesting that the compatibility effect is based on response-response overlap. In both experiments, response preparation impaired accuracy in the visual task. Taken together, these results suggest that response processes and visual encoding share common codes and processes.

Adult↗
PubMed2005

Linking inhibition to activation in the control of task sequences.

Inhibition of abandoned tasks in task switching can be inferred when a worse performance is found with n - 2 task repetitions (ABA sequences) than with nonrepetitions (CBA sequences). Recent evidence has shown that this inhibition effect decreases with long intertrial intervals (i.e., response-cue intervals, RCIs). Two alternatives have been proposed to account for this decrease. One alternative attributes the observed decrease to the decay of inhibition itself. The other alternative proposes that decay of the activation of competing tasks reduces the interference and leads to less inhibition. To decide between these alternatives, we manipulated RCI trialwise. The results favor the decay-of-activation account as an explanation for the decreased inhibition effect. This links the amount of inhibition to the activation level of the competing tasks, whereas evidence for the decay of inhibition remains weak.

Adult↗
PubMed2005

Effects of response selection on the task repetition benefit in task switching.

A task switch typically leads to worse performance than a repetition does. This shift cost can be reduced with sufficient task preparation time, but a residual cost usually remains. We propose that a large part of this residual cost is caused by an activation bias produced by response selection processes in the preceding trial. In our experiments, we manipulated response selection requirements using a go/no-go methodology. The residual shift cost disappeared after no-go trials, suggesting that response selection is crucial to establish an activation bias for the current category-response rules and that this bias persists into the next trial. A comparison with a go-only group confirmed this analysis by revealing no differences in preparatory strategy due to the inclusion of no-go trials. In addition, no-go trials had no significant effects on subsequent trials in a single-task experiment, suggesting that no-go trials are not coded as a task different from go trials and that there is no inhibition of the prepared task in a no-go trial. We thus conclude that a persisting activation bias of response rules plays a major role in task switching.

Adult↗
PubMed2005

Sequential task predictability in task switching.

Many studies of task switching have found that a prolonged preparation time reduces switch costs. An alternative manipulation of task preparation is based on sequential task predictability, rather than preparation time. In Experiments 1 and 2 of the present study, participants performed explicitly instructed task sequences (i.e., AABB) and were then transferred to a random sequence. The observed benefit of predictability-based task preparation was not switch specific. In Experiment 3, the participants changed from random to predictable tasks. The observed predictability benefit again was not switch specific. The data thus suggest that task switching does not necessarily require a switch-specific reconfiguration process. Rather, task-specific control processes may be needed in both task switches and repetitions.

Association Learning↗
PubMed2004

Intention-based and stimulus-based mechanisms in action selection.

Human actions can be classified as being either more stimulus-based or more intention-based. According to the ideomotor framework of action control, intention-based actions primarily refer to anticipated action effects (in other words response-stimulus [R-S] bindings), whereas stimulus-based actions are commonly assumed to be more strongly determined by stimulus-response [S-R] bindings. We explored differences in the functional signatures of both modes of action control in a temporal bisection task. Participants either performed a choice response by pressing one out of two keys in response to a preceding stimulus (stimulus-based action), or pressed one out of two keys to produce the next stimulus (intention-based action). In line with the ideomotor framework, we found intention-based actions to be shifted in time towards their anticipated effects (the next stimulus), whereas stimulus-based actions were shifted towards their preceding stimulus. Event-related potentials (ERPs) in the EEG revealed marked differences in action preparation for the two tasks. The data as a whole provide converging evidence for functional differences in the selection of motor actions as a function of their triggering conditions, and support the notion of two different modes of action selection, one being exogenous or mainly stimulus-driven, the other being endogenous or mainly intention-driven.

Adult↗
PubMed2004

Involuntary retrieval in alphabet-arithmetic tasks: task-mixing and task-switching costs.

This study explores the effects of memory retrieval in task switching. To this end, item-specific stimulus-to-task mappings were manipulated in two "alphabet-arithmetic" experiments. Letter-stimuli were presented and the responses were verbal letter names. The task was either to name the next letter in the alphabet, (e.g., C --> "D," task "plus"), or to name the preceding letter (e.g., C --> "B," task "minus"). The mapping of individual stimuli to the two tasks (and thus to responses) was either consistent (CM) or varied (VM). In Experiment 1, performance was worse for VM items relative to CM items, indicating item-specific task-mapping effects. These task-mapping effects also contributed to mixing costs (i.e., worse performance in mixed-task blocks than in pure-task blocks) but not to switch costs (worse performance in task-switch trials than in repeat trials within mixed blocks). Experiment 2 manipulated pure and mixed tasks between-participants, and the data again showed differential effects of the task-mapping manipulation on mixing costs and switch costs. This suggests that, in these memory-dependent, alphabet-arithmetic tasks, interference due to involuntary task (and/or response) retrieval primarily increases general multi-task effects, such as maintaining activation of the current task.

Adult↗
PubMed2004

Inhibition of response mode in task switching.

Task inhibition was explored in two experiments that employed a paradigm in which participants switched among three tasks. Two tasks required manual choice responses based on numerical judgment (parity or magnitude), whereas a third task required an unconditional double-press of both response keys. Both experiments showed that switching to a just-abandoned task (n-2 task repetition) generally leads to a performance cost relative to switching to another task. Specifically, this task inhibition effect also occurred for the double-press task, suggesting inhibition of response mode. Prolonging the task-cuing interval showed that advance task preparation reduced only inhibition of the double-press task but not of the choice tasks (Experiment 1). Prolonging the response-cue interval led to a decrease of the inhibition effect in all tasks (Experiment 2), suggesting a time-based release of task inhibition. Together, the experiments support the notion of a response-related component of task inhibition.

Adolescent↗