Exploring "phasic" vs. "tonic" accounts of the effect of switch probability on the auditory attention switch cost.

Task-switching experiments have shown that the "switch cost" (poorer performance for task switches than for repetitions) is smaller when the probability of a switch is high (e.g., 0.75) than when it is low (e.g., 0.25). Some theoretical accounts explain this effect in terms of top-down control deployed in advance of the task cue ("pre-cue reconfiguration"). We tested such accounts by manipulating the time available before the onset of the cue (the response-cue interval, RCI), reasoning that top-down pre-cue reconfiguration requires time and therefore its effect should increase with RCI. Participants heard a man and a woman simultaneously speaking number words and categorised the number (< 5 vs. > 5) spoken by the voice specified by a pictorial gender-related cue presented at an RCI of 100 ms or 2,200 ms. The target voice switched with a probability of 0.25 or 0.75 (in separate sessions). In Experiment 1, RTs revealed a large effect of switch probability on the switch cost in the short RCI, which did not increase in the long RCI. Errors hinted at such an increase, but it did not receive clear statistical support and was disconfirmed by a direct and better powered replication in Experiment 2, which fully confirmed the RT pattern from Experiment 1. Thus, the effect of switch probability on the switch cost required little/no time following the response to emerge-it was already at full magnitude at a short RCI-challenging accounts that assume "phasic" deployment of top-down task-set control in advance of the cue.

Morphine exposure modulates dimensional bias and set formation in anthropoids.

Humans demonstrate significant behavioural advantages with particular perceptual dimensions (such as colour or shape) and when the relevant dimension is repeated in consecutive trials. These dimension-related behavioural modulations are significantly altered in neuropsychological and addiction disorders; however, their underlying mechanisms remain unclear. Here, we studied whether these behavioural modulations exist in other trichromatic primate species and whether repeated exposure to opioids influences them. In a target detection task where the target-defining dimension (colour or shape) changed trial by trial, humans exhibited shorter response time (RT) and smaller event-related electrodermal activity with colour dimension; however, macaque monkeys had shorter RT with shape dimension. Although the dimensional biases were in the opposite directions, both species were faster when the relevant dimension was repeated, compared with conditions when it changed, across consecutive trials. These indicate that both species formed dimensional sets and that resulted in a significant 'switch cost'. Scheduled and repeated exposures to morphine, which is analogous to its clinical and recreational use, significantly augmented the dimensional bias in monkeys and also changed the switch cost depending on the relevant dimension. These cognitive effects occurred when monkeys were in abstinence periods (not under acute morphine effects) but expressing significant morphine-induced conditioned place preference. These findings indicate that significant dimensional biases and set formation are evolutionarily preserved in humans' and monkeys' cognition and that repeated exposure to morphine interacts with their manifestation. Shared neural mechanisms might be involved in the long-lasting effects of morphine and expression of dimensional biases and set formation in anthropoids.

Brain connectivity modulation by Bayesian surprise in relation to control demand drives cognitive flexibility via control engagement.

Human control is characterized by its flexibility and adaptability in response to the conditional probability in the environment. Previous studies have revealed that efficient conflict control could be attained by predicting and adapting to the changing control demand. However, it is unclear whether cognitive flexibility could also be gained by predicting and adapting to the changing control demand. The present study aimed to explore this issue by combining the model-based analyses of behavioral and neuroimaging data with a probabilistic cued task switching paradigm. We demonstrated that the Bayesian surprise (i.e. unsigned precision-weighted prediction error [PE]) negatively modulated the connections among stimulus processing brain regions and control regions/networks. The effect of Bayesian surprise modulation on these connections guided control engagement as reflected by the control PE effect on behavior, which in turn facilitated cognitive flexibility. These results bridge a gap in the literature by illustrating the neural and behavioral effect of control demand prediction (or PE) on cognitive flexibility and offer novel insights into the source of switch cost and the mechanism of cognitive flexibility.

Cognitive control is modulated by hierarchical complexity of task switching: An event-related potential study.

The study aimed to explore the effect of hierarchical complexity on task switching. The participants (n = 36) were asked to perform a magnitude or parity judgement on digits (1-9) in the hierarchical simple or complex block. In the simple block, participants made a numerical judgement on the presented digit (1-9) in each trial, whereas in the complex block, they had to first identify whether the digit in the current trial belonged to a predefined category (e.g., whether it was an even number), then perform a numerical judgement or not respond. The behavioural results revealed a significant interaction between hierarchical complexity and transition type (repeat vs. switch), with greater switch cost in the complex than in the simple block. Event-related potentials (ERPs) locked in the cue stage did not reveal this interaction, whereas the ERPs locked in the target stage revealed this interaction during the N2 and P3 time windows, with a larger switch negativity (switch minus repeat) in the complex than in the simple block. These findings demonstrate that an increase in hierarchical complexity triggers increased reactive control in the inhibition of the old task-set and reconfiguration of the new task-set during task switching.

Control mechanisms in voluntary versus mandatory language switching: Evidence from ERPs.

The present study measured event-related potentials (ERP) and behavioral performance to examine whether inhibitory control is involved in voluntary language switching, and if so, to explore the differences in inhibitory control between voluntary and mandatory language switching. Unbalanced Chinese-English bilinguals completed two picture naming tasks: one involving mandatory language switches and one in which participants could voluntarily switch between the two languages. Behavioral data showed significant switch costs and a reversed language dominance effect in both switching tasks. Critically, both effects were larger in mandatory compared to voluntary switching. ERP results revealed that neural switch costs during mandatory switching was significantly different than voluntary switching in both N2 and LPC amplitudes. In contrast, a significant difference in the reversed language dominance effect between both tasks was only observed in LPC amplitude. Together, these findings suggest the involvement of inhibitory control in both mandatory and voluntary language switching, but the degree of inhibition and the time-course of control processes between both tasks appear to be distinct.

Effect of a Strategic Physical Activity Program on Cognitive Flexibility among Children with Internet Addiction: A Pilot Study.

The purpose of this study was to explore whether a strategic physical activity program can improve cognitive flexibility among children with Internet addiction. Ten school-aged children were recruited by distributing flyers at an elementary school in Taiwan. The participants were screened using the Chinese Internet Addiction Scale. Their executive functions were assessed by a task-switching paradigm and their motor competence was evaluated by the Movement Assessment Battery for Children-Second Edition (MABC-2) before and after a 12-week strategic physical activity intervention (twice per week, 90 min per session). The posttest scores showed significant improvements in accuracy in the pure, mixed, and switch trials and in the manual dexterity and total score of the MABC-2 compared with the pretest scores. Despite the inherited limitations of a single group pretest-posttest design this study employed, the findings shed light on the possibility that a strategic physical activity intervention might be a feasible and effective behavioral approach to enhance cognitive function and motor competence in children with Internet addiction. Further studies including a control group, preferably with a randomized controlled trial design, will be needed to validate the findings.

Overlapping but Language-Specific Mechanisms in Morphosyntactic Processing in Highly Competent L2 Acquired at School Entry: fMRI Evidence From an Alternating Language Switching Task.

Many bilingual individuals acquire their second language when entering primary school; however, very few studies have investigated morphosyntax processing in this population. Combining a whole-brain and region of interest (ROI)-based approach, we studied event-related fMRI during morphosyntactic processing, specifically person-number phi-features, in Turkish (L1) and Persian (L2) by highly proficient bilinguals who learned Persian at school entry. In a design with alternating language switching and pseudorandomized grammaticality conditions, two left-lateralized syntax-specific ROIs and 11 bilateral ROIs involved in executive functions (EF) were analyzed for the intensity of activation relative to a resting baseline. Our findings indicate a strong overlap of neural networks for L1 and L2, suggesting structural similarities of neuroanatomical organization. In all ROIs morphosyntactic processing invoked stronger activation in L1 than in L2. This may be a consequence of symmetrical switch costs in the alternating design used here, where the need for suppressing the non-required language is stronger for the dominant L1 when it is non-required as compared to the non-dominant L2, leading to a stronger rebound for L1 than L2 when the language is required. Both L1 and L2 revealed significant activation in syntax-specific areas in left hemisphere clusters and increased activation in EF-specific areas in right-hemisphere than left-hemisphere clusters, confirming syntax-specific functions of the left hemisphere, whereas the right hemisphere appears to subserve control functions required for switching languages. While previous reports indicate a leftward bias in planum temporale activation during auditory and linguistic processing, the present study shows the activation of the right planum temporale indicating its involvement in auditory attention. More pronounced grammaticality effect in left pars opercularis for L1 and in left pSTG for L2 indicate differences in the processing of morphosyntactic information in these brain regions. Nevertheless, the activation of pars opercularis and pSTG emphasize the centrality of these regions in the processing of person-number phi-features. Taken together, the present results confirm that morphosyntactic processing in bilinguals relates to composite, syntax-sensitive and EF-sensitive mechanisms in which some nodes of the language network are differentially involved.

Bilingual Language Control Flexibly Adapts to Cultural Context.

How does bilingual language control adapt to the cultural context? We address this question by looking at the pattern of switch cost and reversed language dominance effect, which are suggested to separately reflect reactive and proactive language control mechanisms, in the contexts with culturally-neutral pictures (i. e., baseline context) or culturally-biased pictures (i.e., congruent context where culture matched the language to be spoken or incongruent context where culture mismatched the language to be spoken). Results showed an asymmetric switch cost with larger costs for L2 in the congruent context as compared with the baseline and incongruent contexts, but the reversed language dominance effect was not changed across contexts, suggesting that cultural context plays a critical role in modulating reactive but not proactive language control. These findings reveal the dynamic nature of language control in bilinguals and have important implications for the current models of bilingual language control.

Partitioning switch costs when investigating task switching in relation to media multitasking.

The prevalence of media multitasking - the concurrent use of multiple forms of media - has motivated research on whether and how it is related to various cognitive abilities, such as the ability to switch tasks. However, previous research on the relationship between media multitasking and task-switching performance has yielded mixed results, possibly because of small sample sizes and a confound between task and cue transitions that resulted in switch costs being impure measures of task-switching ability. The authors conducted a large-sample study in which media multitasking behavior was surveyed and task-switching performance was assessed using two cues per task, thereby allowing switch costs to be partitioned into task-switching and cue-repetition effects. The main finding was no evidence of any relationship between media multitasking scores and task-switching effects (or cue-repetition effects), either in correlational analyses or in extreme group analyses of light and heavy media multitaskers. The results are discussed in the context of previous research, with implications for studying media multitasking in relation to task-switching performance.

Top-down task-specific determinants of multisensory motor reaction time enhancements and sensory switch costs.

This study was designed to investigate the complex interplay between multisensory processing, top-down processes related to the task relevance of sensory signals, and sensory switching. Thirty-five adults completed either a speeded detection or a discrimination task using the same auditory and visual stimuli and experimental setup. The stimuli consisted of unisensory and multisensory presentations of the letters 'b' and 'd'. The multisensory stimuli were either congruent (e.g., the grapheme 'b' with the phoneme /b/) or incongruent (e.g., the grapheme 'b' with the phoneme /d/). In the detection task, the participants had to respond to all of the stimuli as rapidly as possible while, in the discrimination task, they only responded on those trials where one prespecified letter (either 'b' or 'd') was present. Incongruent multisensory stimuli resulted in faster responses as compared to unisensory stimuli in the detection task. In the discrimination task, only the dual-target congruent stimuli resulted in faster RTs, while the incongruent multisensory stimuli led to slower RTs than to unisensory stimuli; RTs were the slowest when the visual (rather than the auditory) signal was irrelevant, thus suggesting visual dominance. Switch costs were also observed when switching between unisensory target stimuli, while dual-target multisensory stimuli were less likely to be affected by sensory switching. Taken together, these findings suggest that multisensory motor enhancements and sensory switch costs are influenced by top-down modulations determined by task instructions, which can override the influence of prior learnt associations.

An Experimenter's Influence on Motor Enhancements: The Effects of Letter Congruency and Sensory Switch-Costs on Multisensory Integration.

Multisensory integration can alter information processing, and previous research has shown that such processes are modulated by sensory switch costs and prior experience (e.g., semantic or letter congruence). Here we report an incidental finding demonstrating, for the first time, the interplay between these processes and experimental factors, specifically the presence (vs. absence) of the experimenter in the testing room. Experiment 1 demonstrates that multisensory motor facilitation in response to audiovisual stimuli (circle and tone with no prior learnt associations) is higher in those trials in which the sensory modality switches than when it repeats. Those participants who completed the study while alone exhibited increased RT variability. Experiment 2 replicated these findings using the letters "b" and "d" presented as unisensory stimuli or congruent and incongruent multisensory stimuli (i.e., grapheme-phoneme pairs). Multisensory enhancements were inflated following a sensory switch; that is, congruent and incongruent multisensory stimuli resulted in significant gains following a sensory switch in the monitored condition. However, when the participants were left alone, multisensory enhancements were only observed for repeating incongruent multisensory stimuli. These incidental findings therefore suggest that the effects of letter congruence and sensory switching on multisensory integration are partly modulated by the presence of an experimenter.

How a crisis mindset activates implicit knowledge and brings it into awareness: The role of attentional switch cost.

In this study, we relied on the attentional switch cost to ascertain whether a crisis mindset can activate and momentarily bring related implicit knowledge into awareness. We found that the attentional switch cost was higher in a crisis mindset condition than in a common mindset condition in which non-crisis-related stimuli were being attended to (Experiment 1). However, the attentional switch cost was lower in the crisis mindset condition when crisis-related stimuli were being attended to (Experiment 2A), and the reduced cost was not attributable to the complexity of the stimuli (Experiment 2B). A link emerged in the crisis mindset condition between the attentional switch cost and related implicit knowledge (Experiment 3A and 3B). Potential confounding factors were adequately controlled (see the Appendix). In conclusion, the results offer insight into the pivotal role of a crisis mindset. This finding delineates an alternative pathway in which implicit knowledge can be activated and brought into working memory once an event is perceived and interpreted as a crisis.

High Cognitive Flexibility Learners Perform Better in Probabilistic Rule Learning.

Cognitive flexibility reflects the ability to switch quickly between tasks or stimulus sets, which is an important feature of human intelligence. Researchers have confirmed that this ability is related to the learners' academic achievement, cognitive ability, and creativity development. The number-letter switching task is an effective tool for measuring cognitive flexibility. Previous studies have found that high flexibility individuals perform better in rule-based tasks such as the Iowa Gambling Task. It is not clear whether highly flexible learners have learning advantages when the rule tasks involve probabilistic cues. Using an inter-individual differences approach, we examined whether cognitive flexibility, as assessed by the number-letter task, is associated with the learning process of a probabilistic rule task. The results showed that the high flexibility group reached a higher level of rule acquisition, and the accuracy during the post-learning stage was significantly higher than the low flexibility group. These findings demonstrate that cognitive flexibility is associated with the performance after the rule acquisition during the probabilistic rule task. Future research should explore the internal process of learning differences between high and low flexibility learners by using other technologies across multiple modes.

The role of domain-general inhibition in inflectional encoding: Producing the past tense.

According to a prominent account of inflectional encoding (Pinker, 1999; Pinker & Ullman, 2002b), regular forms are encoded by a rule-governed combination of stems and affixes, whereas irregular forms are retrieved from memory while inhibiting rule application. Sahin, Pinker, and Halgren (2006) suggested that this concerns a domain-general mechanism. Previous research on domain-general inhibition has shown that when switching between tasks, languages, or phrase types, an asymmetrical switch cost is obtained, which has been attributed to overcoming previous inhibition of the predominant response. If generating an irregular form involves rule inhibition, then switching from an irregular to a regular form should require overcoming previous inhibition and delay responding. We tested this in three experiments on producing the past tense in Dutch. We observed that an asymmetrical switch cost is obtained when switching between inflecting and reading verbs, but not when switching between encoding irregular and regular forms. These results suggest that the production of irregular forms does not involve the type of domain-general inhibition involved in switching between tasks, languages, or phrase types.

Multilingual two-digit number naming: The influence of composition rules on language switching.

The aim of this study was to examine language switching in a two-digit number naming task. In contrast to single digits, two-digit numbers have a composition rule (i.e., morphological configuration) that may differ between languages. For example, the Arabic number 21 is read with an inverted composition rule in German (unit before decade) and a non-inverted composition rule in English (decade before unit). In the present experiment, one group of German native speakers and one group of Spanish native speakers had to name two-digit numbers in German, English, or Spanish. The results demonstrate a language-switch cost, revealing better performance in language repetition than in language-switch trials. This switch cost was further modulated by repeating or switching the composition rule, since the language repetition benefit (i.e., the switch cost) was reduced in trials with composition-rule switches compared with trials with composition-rule repetitions. This finding indicates that the language in which the number word has to be produced and its composition rule are not switched independently but rather may be integrated into one language schema.

Dynamics of inhibitory control during bilingual speech production: An electrophysiological study.

Bilingual speakers have to control their languages to avoid interference, which may be achieved by enhancing the target language and/or inhibiting the nontarget language. Previous research suggests that bilinguals use inhibition (e.g., Jackson et al., 2001), which should be reflected in the N2 component of the event-related potential (ERP) in the EEG. In the current study, we investigated the dynamics of inhibitory control by measuring the N2 during language switching and repetition in bilingual picture naming. Participants had to name pictures in Dutch or English depending on the cue. A run of same-language trials could be short (two or three trials) or long (five or six trials). We assessed whether RTs and N2 changed over the course of same-language runs, and at a switch between languages. Results showed that speakers named pictures more quickly late as compared to early in a run of same-language trials. Moreover, they made a language switch more quickly after a long run than after a short run. This run-length effect was only present in the first language (L1), not in the second language (L2). In ERPs, we observed a widely distributed switch effect in the N2, which was larger after a short run than after a long run. This effect was only present in the L2, not in the L1, although the difference was not significant between languages. In contrast, the N2 was not modulated during a same-language run. Our results suggest that the nontarget language is inhibited at a switch, but not during the repeated use of the target language.

Not inertia but reconfiguration: Asymmetric switch cost in a hierarchical task.

Numerous studies have investigated asymmetric switch cost between different types of tasks. However, the underlying neural mechanism of asymmetric switch cost in a hierarchical task remains unknown. In the present study, we used a representation-nested paradigm and defined three hierarchical levels of number comparison. Participants were required to switch between different levels according to the color of the stimuli. Behavioral result showed a longer response time in the upward switch (from the lower level to the middle level) than in the downward switch (from the higher level to the middle level). The event related potential results showed that (1) a larger N2 was elicited by the upward switch, which reflects the response inhibition process; and (2) the sustained potential component was most negative for the upward switch and least negative for the repeat condition, thereby reflecting the different degrees of reconfiguration of task set. The reverse asymmetric switch cost in the hierarchical task was explained using task-set reconfiguration theory and related to the activation of the left frontal region.

The Roles of Relative Linguistic Proficiency and Modality Switching in Language Switch Cost: Evidence from Chinese Visual Unimodal and Bimodal Bilinguals.

The current study investigated the mechanism of language switching in unbalanced visual unimodal bilinguals as well as balanced and unbalanced bimodal bilinguals during a picture naming task. All three groups exhibited significant switch costs across two languages, with symmetrical switch cost in balanced bimodal bilinguals and asymmetrical switch cost in unbalanced unimodal bilinguals and bimodal bilinguals. Moreover, the relative proficiency of the two languages but not their absolute proficiency had an effect on language switch cost. For the bimodal bilinguals the language switch cost also arose from modality switching. These findings suggest that the language switch cost might originate from multiple sources from both outside (e.g., modality switching) and inside (e.g., the relative proficiency of the two languages) the linguistic lexicon.

Effect of Acute Exercise Mode on Serum Brain-Derived Neurotrophic Factor (BDNF) and Task Switching Performance.

Previous studies have consistently reported a positive effect of acute exercise on cognition, particularly on executive function. However, most studies have focused on aerobic and resistant forms of exercise. The purpose of this study was to compare the effect of 'open-skill' with 'closed-skill' exercise (defined in terms of the predictability of the performing environment) on brain-derived neurotrophic factor (BDNF) production and task switching performance. Twenty young adult males participated in both closed (running) and open (badminton) skill exercise sessions in a counterbalanced order on separate days. The exercise sessions consisted of 5 min of warm up exercises followed by 30 min of running or badminton. The exercise intensity was set at 60% (±5%) of the heart rate reserve level (HRR) with HR being monitored by a wireless heart rate monitor. Blood samples were taken and participation in a task-switching paradigm occurred before and after each exercise session. Results showed no differences in serum BDNF or task-switching performance at the pre-test stage, however, badminton exercise resulted in significantly higher serum BDNF levels (a proxy for levels of BDNF in the brain) and near significant smaller global switching costs relative to running. This study has provided preliminary evidence in support the relative benefits of open-skills exercises on BDNF and executive function.

Effect of variability of sequence length of go trials preceding a stop trial on ability of response inhibition in stop-signal task.

This study investigated whether the variability of the sequence length of the go trials preceding a stop trial enhanced or interfered with inhibitory control. The hypotheses tested were either inhibitory control improves when the sequence length of the go trials varies as a consequence of increased preparatory effort or it degrades as a consequence of the switching cost from the go trial to the stop trial. The right-handed participants abducted the left or right index finger in response to a go cue during the go trials. A stop cue was given at 50, 90, or 130 ms after the go cue, with 0.25 probability in the stop trial. In the less variable session, a stop trial was presented after two, three, or four consecutive go trials. In the variable session, a stop trial was presented after one, two, three, four, or five consecutive go trials. The reaction time and stop-signal reaction time were not significantly different between the sessions and between the response sides. Nevertheless, the probability of successful inhibition of the right-hand response in the variable session was higher than that in the less variable session when the stop cue was given 50 ms after a go cue. This finding supports the view that preparatory effort due to less predictability of the chance of a forthcoming response inhibition enhances the ability of the right-hand response inhibition when the stop process begins earlier.