The role of inhibition in the regulation of sequential action

Dual route for subtask order control: Evidence from the psychological refractory paradigm

A change in subtask order in the psychological refractory period (PRP) paradigm increases the effect of stimulus onset asynchrony (SOA) on the second response. We used a paradigm with cued, randomly determined subtask order to test the hypothesis that this SOA by order switch overadditivity reflects order control, via “copying” stimulus order. In Experiments 1a and 1b, overadditivity was evident only with insufficient opportunity for cue-based order control. In Experiment 2, overadditivity was decreased by using the same set of stimuli in the two subtasks, presumably by removing the opportunity to rely on stimulus order. In Experiment 3, removing the order cue increased the overadditivity, presumably because control was based solely upon copying stimulus order. The results indicate interactive top-down and bottom-up order control. Implications to theories of the PRP paradigm are discussed.

On the importance of being first: serial order effects in the interaction between action plans and ongoing actions

When we plan sequences of actions, we must hold some elements of the sequence in working memory (WM) while we execute others. Research shows that execution of an action can be delayed if it partly overlaps (vs. does not overlap) with another action plan maintained in WM (partial repetition cost). However, it is not known whether all features of the action maintained in WM interfere equally with current actions. Most serial models of memory and action assume that interference will be equal, because all action features in the sequence should be activated to an equal degree in parallel; others assume that action features earlier in the sequence will interfere more than those later in the sequence, because earlier features will be more active. Using a partial repetition paradigm, this study examined whether serial position of action features in action sequences maintained in WM have an influence on current actions. Two stimulus events occurred in a sequence, and participants planned and maintained an action sequence to the first event (action A) in WM while executing a speeded response to the second event (action B). Results showed delayed execution of action B when it matched the first feature in the action A sequence (partial repetition cost), but not when it matched the last feature. These findings suggest that serial order is represented in the action plan prior to response execution, consistent with models that assume that serial order is represented by a primacy gradient of parallel feature activation prior to action execution.

Distraction during learning with hypermedia: difficult tasks help to keep task goals on track

In educational hypermedia environments, students are often confronted with potential sources of distraction arising from additional information that, albeit interesting, is unrelated to their current task goal. The paper investigates the conditions under which distraction occurs and hampers performance. Based on theories of volitional action control it was hypothesized that interesting information, especially if related to a pending goal, would interfere with task performance only when working on easy, but not on difficult tasks. In Experiment 1, 66 students learned about probability theory using worked examples and solved corresponding test problems, whose task difficulty was manipulated. As a second factor, the presence of interesting information unrelated to the primary task was varied. Results showed that students solved more easy than difficult probability problems correctly. However, the presence of interesting, but task-irrelevant information did not interfere with performance. In Experiment 2, 68 students again engaged in example-based learning and problem solving in the presence of task-irrelevant information. Problem-solving difficulty was varied as a first factor. Additionally, the presence of a pending goal related to the task-irrelevant information was manipulated. As expected, problem-solving performance declined when a pending goal was present during working on easy problems, whereas no interference was observed for difficult problems. Moreover, the presence of a pending goal reduced the time on task-relevant information and increased the time on task-irrelevant information while working on easy tasks. However, as revealed by mediation analyses these changes in overt information processing behavior did not explain the decline in problem-solving performance. As an alternative explanation it is suggested that goal conflicts resulting from pending goals claim cognitive resources, which are then no longer available for learning and problem solving.

Response-repetition costs in choice-RT tasks: biased expectancies or response inhibition?

Repetition effects are often viewed as informative regarding the cognitive mechanisms of action control. One particular finding, namely costs for repeating the same response in subsequent trials, especially challenges theorizing. Costs for response repetitions have recently been reported in task-switch studies on task-switch trials (whereas benefits usually arise in task-repetition trials), but also in some choice-RT task studies. In three experiments, two of the most successful accounts for the response-repetition costs in choice-RT task studies and task switching were tested: an expectancy-based explanation, and an inhibition-based account. Using a choice-RT task introduced by Smith (1968) and manipulating the response-stimulus interval (RSI) and the categorizability of the stimuli, some specific predictions of the two accounts were tested. The results clearly revealed that expectancy-based explanations fail to account for the observed patterns of effects, whereas they are well in line with the predictions from the inhibition-based account. Finally, the results are further discussed with respect to alternative accounts from the field of task switching.

Analogous mechanisms of selection and updating in declarative and procedural working memory: experiments and a computational model

The article investigates the mechanisms of selecting and updating representations in declarative and procedural working memory (WM). Declarative WM holds the objects of thought available, whereas procedural WM holds representations of what to do with these objects. Both systems consist of three embedded components: activated long-term memory, a central capacity-limited component for building structures through temporary bindings, and a single-element focus of attention. Five experiments test the hypothesis of analogous mechanisms in declarative and procedural WM, investigating repetition effects across trials for individual representations (objects and responses) and for sets (memory sets and task sets), as well as set-congruency effects. Evidence for analogous processes was obtained from three phenomena: (1) Costs of task switching and of list switching are reduced with longer preparation interval. (2) The effects of task congruency and of list congruency are undiminished with longer preparation interval. (3) Response repetition interacts with task repetition in procedural WM; here we show an analogous interaction of list repetition with item repetition in declarative WM. All three patterns were reproduced by a connectionist model implementing the assumed selection and updating mechanisms. The model consists of two modules, an item-selection module selecting individual items from a memory set, or responses from a task set, and a set-selection module for selecting memory sets or task sets. The model codes the matrix of binding weights in the item-selection module as a pattern of activation in the set-selection module, thereby providing a mechanism for building chunks in LTM, and for unpacking them as structures into working memory.

Sequence Learning Under Uncertainty in Children: Self-Reflection vs. Self-Assertion

We know that stochastic feedback impairs children’s associative stimulus–response (S–R) learning (Crone et al., 2004a; Eppinger et al., 2009), but the impact of stochastic feedback on sequence learning that involves deductive reasoning has not been not tested so far. In the current study, 8- to 11-year-old children (N = 171) learned a sequence of four left and right button presses, LLRR, RRLL, LRLR, RLRL, LRRL, and RLLR, which needed to be deduced from feedback because no directional cues were given. One group of children experienced consistent feedback only (deterministic feedback, 100% correct). In this condition, green feedback on the screen indicated that the children had been right when they were right, and red feedback indicated that the children had been wrong when they were wrong. Another group of children experienced inconsistent feedback (stochastic feedback, 85% correct, 15% false), where in some trials, green feedback on the screen could signal that children were right when in fact they were wrong, and red feedback could indicate that they were wrong when in fact they had been right. Independently of age, children’s sequence learning in the stochastic condition was initially much lower than in the deterministic condition, but increased gradually and improved with practice. Responses toward positive vs. negative feedback varied with age. Children were increasingly able to understand that they could have been wrong when feedback indicated they were right (self-reflection), but they remained unable to understand that they could have been right when feedback indicated they were wrong (self-assertion).

The role of age and inhibitory efficiency in working memory processing and storage components

In this study, we examined the extent to which inhibitory efficiency accounted for age-related decline in the processing and storage components of working memory. Older and younger adults performed a sequential task, which served as an index of deletion-type inhibition (the ability to suppress no-longer-relevant information). The reading span task was used to measure working memory components by examining processing accuracy, processing time, and end-word recall of sentences presented. Reduced inhibitory efficiency, which was poorer in older adults, predicted age-related decline in recall, over and above the effects of processing speed. Similar results were observed for processing accuracy, although the age effect in this component was marginal. These results highlight the important role of deletion-type inhibition in explaining age-related decline in working memory performance, particularly in the storage component, and extend previous research by examining this relationship at a componential level.

Response-repetition effects in task switching with and without response execution

Previous research into the mechanisms of task switching has shown that repeating the same response in a different task context is associated with costs. To investigate whether such response-repetition costs occur even when the first of the two responses is not overtly executed, we used a variant of the change-signal paradigm. Subjects responded to a first stimulus by pressing a left or right response key. In half of the trials, a second stimulus occurred after a variable, adaptively adjusted delay, indicating to abandon the first response, and only respond to the second stimulus using another set of left and right response keys. In Experiment 1, different tasks had to be performed with the first and second stimulus (task-switch condition); in Experiment 2, the same task had to be performed with both stimuli (task-repetition condition). Response-repetition costs were obtained in Experiment 1, and response-repetition benefits in Experiment 2. Importantly, these costs and benefits were obtained even when the first of the two responses had not been overtly executed. The data support the idea that interference of task-specific response codes occurs at the level of abstract response codes. Interference of such response codes occurs even when the responses are not overtly executed.

Sequential performance in young and older adults: evidence of chunking and inhibition

Two experiments were conducted to examine possible sources of age-related decline in sequential performance: age differences in sequence representation, retrieval of sequence elements, and efficiency of inhibitory processes. Healthy young and older participants learned a sequence of eight animal drawings in fixed order, then monitored for these targets within trials of mis-ordered stimuli, responding only when targets were shown in the correct order. Responses were slower for odd numbered targets, suggesting that participants spontaneously organized the sequence in two-element chunks. Perseverations (responses to previously relevant targets) served as an index of inhibitory inefficiency. Efficiency of chunk retrieval and self-inhibition were lower for older than for younger adults. Increasing environmental support in Experiment 2 through overt articulation of current chunk elements showed a pattern of results similar to Experiment 1, with particular benefit for older adults. The findings suggest an underlying susceptibility to interference in old age.

The influence of age and physical activity on upper limb proprioceptive ability

Our understanding of age-related declines in upper limb proprioceptive abilities is limited. Furthermore, the extent to which physical activity might ameliorate age-related changes in proprioception is not known. Upper limb proprioceptive acuity was examined in young and older (active and sedentary) right-handed adults using a wrist-position-matching task that varied in terms of processing demands. Older individuals were also classified according to their participation in tasks specific to the upper limb. Errors were greater for older than younger individuals. Older sedentary adults showed greater errors and performed movements less smoothly than older active adults. The nonspecific group showed greater errors and longer movement times than the upper-limb-specific group. In older adults, decreased ability to perceive limb position may be related to a sedentary lifestyle and declines associated with memory and transfer of proprioceptive information. Performing tasks specific to the upper limbs may reduce age-related declines in proprioception.

Adaptive control of response preparedness in task switching

When rapidly switching between two tasks, bivalent stimuli can accidentally trigger the previously executed and therefore still activated response. Recently, it has been suggested that behavioral response-repetition effects reflect response inhibition that reduces the risk of such erroneous response repetitions. The present study investigated neural correlates of this inhibition process using lateralized readiness potentials (LRP). In three experiments, we demonstrate a response-switch bias emerging during the preparatory interval which is independent of task sequence (Experiment 1), which is linked to task preparation (Experiment 2), and which is present only under task-switching conditions (Experiment 3). These results suggest that the bias reflects a control process that adaptively regulates response preparedness.

Attentional switching in the sequential flanker task: age, location, and time course effects

The sequential flanker task was developed to study sequential performance using methodology borrowed from studies of task switching. We investigated age differences in backward inhibition [BI: Mayr, U., & Keele, S. W. (2000). Changing internal constraints on action: The role of backward inhibition. Journal of Experimental Psychology: General, 129, 4-26] during a sequential category search task. Participants learned four animal categories in a fixed order, and then searched for exemplars from those categories in runs of mis-ordered exemplars. Across three experiments, we observed robust BI facilitation effects. However, the magnitude of BI effects did not differ across age groups. This age-invariance held despite manipulations of distractibility (Experiment 2), and interstimulus interval (Experiment 3), suggesting that BI processes may be relatively automatic and obligatory in the context of sequential tasks. The findings are discussed in terms of the attentional mechanisms that underlie task set switching and sequential performance.

The function of phenomenal states: supramodular interaction theory

Discovering the function of phenomenal states remains a formidable scientific challenge. Research on consciously penetrable conflicts (e.g., "pain-for-gain" scenarios) and impenetrable conflicts (as in the pupillary reflex, ventriloquism, and the McGurk effect [H. McGurk & J. MacDonald, 1976]) reveals that these states integrate diverse kinds of information to yield adaptive action. Supramodular interaction theory proposes that phenomenal states play an essential role in permitting interactions among supramodular response systems--agentic, independent, multimodal, information-processing structures defined by their concerns (e.g., instrumental action vs. certain bodily needs). Unlike unconscious processes (e.g., pupillary reflex), these processes may conflict with skeletal muscle plans, as described by the principle of parallel responses into skeletal muscle (PRISM). Without phenomenal states, these systems would be encapsulated and incapable of collectively influencing skeletomotor action.

ADHD outside the laboratory: boys' executive function performance on tasks in videogame play and on a visit to the zoo

One current theory of attention-deficit/hyperactivity disorder (ADHD) proposes that a primary deficit in behavioral inhibition gives rise to secondary deficits in 4 executive functions and motor control. To date, empirical support for this model is based primarily on laboratory-based cognitive methods. This study assessed behavioral inhibition and executive functioning in children with ADHD in 2 real-life contexts: videogames (motor-skill target game, cognitively demanding adventure game) and an outing at the zoo (route tasks). Participants were a community sample of 57 boys diagnosed with ADHD (20 inattentive, 37 combined type) and 57 normally developing control boys, matched individually for age and nonverbal IQ. Operationally defined measures of behavioral inhibition and specific executive functions were derived from these activities and assessed under contrasting conditions of low or high working memory and distractor loads. There were no group differences in basic motor skills on the target game, nor in terms of the ability to inhibit a prepotent or ongoing response in the adventure videogame. However, boys with ADHD exhibited more self-talk, more effortful response preparation, and completed fewer challenges in the latter videogame. Also, they manifested inhibition deficits in terms of interference control during the route task at the zoo and took longer to complete the tasks. Typically, these differences were greatest under conditions of high working memory and distractor loads. Findings from this study suggest that cognitive difficulties in ADHD may be context dependent and that ADHD is associated with deficits in some but not all aspects of behavioral inhibition.

Age-related changes in task-switching components: the role of task uncertainty

The present study examined age differences in executive functioning, using an externally cued task-switching paradigm. Two components of task switching were assessed: the ability to maintain and select among task sets (general switch costs) and the ability to switch between task sets (specific switch costs). In contrast to previous findings, we found large age-related differences in specific switch costs, especially when the number of potentially relevant task sets is increased from two to four. Age-related differences in general switch costs were absent when external task cues subserved executive processing in task switching. Generally, the findings suggest that age-related impairments in task-switching components vary as a function of task uncertainty, such as the presence of environmental prompts to behavior.