Transcranial alternating current stimulation barely enhances working memory in healthy adults: A meta-analysis.

Working memory (WM) is a pivotal neural mechanism for cognitive function and ability. Transcranial alternating current stimulation (tACS) was used to improve WM by entraining key brain rhythms. We submitted to meta-analysis 143 effects of tACS on WM performance, found in 42 reports published between 2014 and 2023, encompassing a total of 1386 healthy adults stimulated. The overall effect size of 134 interventions intended to improve WM equaled Hedges' g = 0.076 [0.039, 0.113]. However, after correcting for a significant publication bias this effect size dropped to zero. By contrast, 9 interventions distorting the brain synchronization using antiphase tACS reliably decreased WM performance, with Hedges' g = -0.266, [-0.458, -0.074]. Individuating the targeted frequency band was the only reliable moderator. The disparity between our null outcome and moderately positive tACS effects estimated by previous meta-analyses resulted from our inclusion of the most recent studies mostly reporting negligible effects. Our results suggest that current tACS protocols barely enhance WM in healthy adults. More research is needed to develop effective methods for WM stimulation.

No effects of the theta-frequency transcranial electrical stimulation for recall, attention control, and relation integration in working memory.

Introduction: Recent studies have suggested that transcranial alternating current stimulation (tACS), and especially the theta-frequency tACS, can improve human performance on working memory tasks. However, evidence to date is mixed. Moreover, the two WM tasks applied most frequently, namely the n-back and change-detection tasks, might not constitute canonical measures of WM capacity. Method: In a relatively large sample of young healthy participants (N = 62), we administered a more canonical WM task that required stimuli recall, as well as we applied two WM tasks tapping into other key WM functions: attention control (the antisaccade task) and relational integration (the graph mapping task). The participants performed these three tasks three times: during the left frontal 5.5-Hz and the left parietal 5.5-Hz tACS session as well as during the sham session, with a random order of sessions. Attentional vigilance and subjective experience were monitored. Results: For each task administered, we observed significant gains in accuracy neither for the frontal tACS session nor for the parietal tACS session, as compared to the sham session. By contrast, the scores on each task positively inter-correlated across the three sessions. Discussion: The results suggest that canonical measures of WM capacity are strongly stable in time and hardly affected by theta-frequency tACS. Either the tACS effects observed in the n-back and change detection tasks do not generalize onto other WM tasks, or the tACS method has limited effectiveness with regard to WM, and might require further methodological advancements.

Schizophrenia patients perform as well as healthy controls on creative problem solving when fluid intelligence is accounted for.

INTRODUCTION: This study examined creative problem solving in schizophrenia. We aimed to verify three hypotheses: (H1) schizophrenia patients differ from healthy controls in the accuracy of creative problem solving; (H2) schizophrenia patients are less effective at evaluating and rejecting incorrect associations and (H3) have a more idiosyncratic way of searching for semantic associations compared to controls. METHODS: Six Remote Associates Test (RAT) items and three insight problems were applied to schizophrenia patients and healthy controls. We compared groups on the overall accuracy in the tasks to verify H1 and developed a novel method of comparing the patterns of errors in the RAT to verify H2 and H3. We controlled for fluid intelligence to eliminate this significant source of variation, as typically creativity and intelligence are significantly related. RESULTS: Bayesian factor analysis did not support the group differences in either insight problems and RAT accuracy or the patterns of RAT errors. CONCLUSIONS: The patients performed as well as the controls on both tasks. Analysis of RAT errors suggested that the process of searching for remote associations is comparable in both groups. It is highly improbable that individuals with schizophrenia benefit from their diagnosis during creative problem solving.

Graph Mapping: A novel and simple test to validly assess fluid reasoning.

We present Graph Mapping - a simple and effective computerized test of fluid intelligence (reasoning ability). The test requires structure mapping - a key component of the reasoning process. Participants are asked to map a pair of corresponding nodes across two mathematically isomorphic but visually different graphs. The test difficulty can be easily manipulated - the more complex structurally and dissimilar visually the graphs, the higher response error rate. Graph Mapping offers high flexibility in item generation, ranging from trivial to extremally difficult items, supporting progressive item sequences suitable for correlational studies. It also allows multiple item instances (clones) at a fixed difficulty level as well as full item randomization, both particularly suitable for within-subject experimental designs, longitudinal studies, and adaptive testing. The test has short administration times and is unfamiliar to participants, yielding practical advantages. Graph Mapping has excellent psychometric properties: Its convergent validity and reliability is comparable to the three leading traditional fluid reasoning tests. The convenient software allows a researcher to design the optimal test variant for a given study and sample. Graph Mapping can be downloaded from: https://osf.io/wh7zv/.

Bilingualism caught in a net: A new approach to understanding the complexity of bilingual experience.

The growing importance of research on bilingualism in psychology and neuroscience motivates the need for a psychometric model that can be used to understand and quantify this phenomenon. This research is the first to meet this need. We reanalyzed two data sets (N = 171 and N = 112) from relatively young adult language-unbalanced bilinguals and asked whether bilingualism is best described by the factor structure or by the network structure. The factor and network models were established on one data set and then validated on the other data set in a fully confirmatory manner. The network model provided the best fit to the data. This implies that bilingualism should be conceptualized as an emergent phenomenon arising from direct and idiosyncratic dependencies among the history of language acquisition, diverse language skills, and language-use practices. These dependencies can be reduced to neither a single universal quotient nor to some more general factors. Additional in-depth network analyses showed that the subjective perception of proficiency along with language entropy and language mixing were the most central indices of bilingualism, thus indicating that these measures can be especially sensitive to variation in the overall bilingual experience. Overall, this work highlights the great potential of psychometric network modeling to gain a more accurate description and understanding of complex (psycho)linguistic and cognitive phenomena. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Fluid Intelligence Emerges from Representing Relations.

Based on recent findings in cognitive neuroscience and psychology as well as computational models of working memory and reasoning, I argue that fluid intelligence (fluid reasoning) can amount to representing in the mind the key relation(s) for the task at hand. Effective representation of relations allows for enormous flexibility of thinking but depends on the validity and robustness of the dynamic patterns of argument-object (role-filler) bindings, which encode relations in the brain. Such a reconceptualization of the fluid intelligence construct allows for the simplification and purification of its models, tests, and potential brain mechanisms.

Uncovering the course of analogical mapping using eye tracking.

Analogical mapping - the core component of analogical reasoning - consists of establishing the relational structure shared by two analogous situations and inferring the missing elements in a less familiar situation from a more familiar one. Several existing models of analogy predicted that the complete relational structure can be considered in parallel. Other models postulated that mapping can be less or more incremental - it can access only a relatively small part of the structure, and needs to move to its other parts in steps in order to construct the final relational correspondence. However, the precise time course of analogical mapping, especially in sufficiently complex analogies, to date was rarely studied empirically. In two studies, eye tracking was used to assess in a rigorous way the extent to which mapping can be incremental. In a newly designed geometric A:B::C:D task, pattern D was generated from C according to the same shape transformations that generated pattern B from A. The six possible response options differed systematically in the number of correct transformations, from no transformation matching, via partial relational match, up to the full match. In Study 1, the relational match of options fixated on by participants was initially low but increased monotonically over the course of analogy. The number of corresponding eye fixations predicted 68% variance in relational match of the final response. The correct option was chosen only if fixated on for a sufficiently long time. Study 2 replicated the findings using a more ecologically valid and less demanding task variant that required to map the changes in people's appearance. The results support these theoretical models of analogy which postulate strictly incremental mapping.

Various sources of distraction during analogical reasoning.

Reasoning by analogy requires mapping relational correspondence between two situations to transfer information from the more familiar (source) to the less familiar situation (target). However, the presence of distractors may lead to invalid conclusions based on semantic or perceptual similarities instead of on relational correspondence. To understand the role of distraction in analogy making, we examined semantically rich four-term analogies (A:B::C:?) and scene analogies, as well as semantically lean geometric analogies and the matrix task tapping general reasoning. We examined (a) what types of lures were most distracting, (b) how the two semantically rich analogy tasks were related, and (c) how much variance in the scores could be attributed to general reasoning ability. We observed that (a) in four-term analogies the distractors semantically related to C impacted performance most strongly, as compared to the perceptual, categorical, and relational distractors, but the two latter distractor types also mattered; (b) distraction sources in four-term and scene analogies were virtually unrelated; and (c) general reasoning explained the largest part of variance in resistance to distraction. The results suggest that various sources of distraction operate at different stages of analogical reasoning and differently affect specific analogy paradigms.

How physical interaction with insight problems affects solution rates, hint use, and cognitive load.

So-called insight problems are widely studied because they tap into the creative thinking that is crucial for solving real problems. However, insight problems are typically presented in static formats (on paper, computer) that allow no physical interaction with the problem elements, whereas such an interaction might in fact reduce the load on limited cognitive resources, such as working memory (WM) capacity, thereby facilitating solutions. To test this proposition, 124 young adults were allowed to interact physically with nine established insight problems, while another 124 people attempted to solve these problems using paper and pencil. Additionally, hints were provided for three problems that typically no-one solves. No general facilitating effect of physical interaction was found, with only one problem clearly benefitting from it. Furthermore, making use of hints was actually hindered by physical interaction. No difference in perceived task load and correlation with WM capacity was observed between the formats, and subjective ratings of insight were virtually unaffected by presentation format. Overall, physical interaction minimally affected insight problem-solving, which appears to rely strongly on internalized cognitive processing involving WM.

Spatiotemporal complexity patterns of resting-state bioelectrical activity explain fluid intelligence: Sex matters.

Neural complexity is thought to be associated with efficient information processing but the exact nature of this relation remains unclear. Here, the relationship of fluid intelligence (gf) with the resting-state EEG (rsEEG) complexity over different timescales and different electrodes was investigated. A 6-min rsEEG blocks of eyes open were analyzed. The results of 119 subjects (57 men, mean age = 22.85 ± 2.84 years) were examined using multivariate multiscale sample entropy (mMSE) that quantifies changes in information richness of rsEEG in multiple data channels at fine and coarse timescales. gf factor was extracted from six intelligence tests. Partial least square regression analysis revealed that mainly predictors of the rsEEG complexity at coarse timescales in the frontoparietal network (FPN) and the temporo-parietal complexities at fine timescales were relevant to higher gf. Sex differently affected the relationship between fluid intelligence and EEG complexity at rest. In men, gf was mainly positively related to the complexity at coarse timescales in the FPN. Furthermore, at fine and coarse timescales positive relations in the parietal region were revealed. In women, positive relations with gf were mostly observed for the overall and the coarse complexity in the FPN, whereas negative associations with gf were found for the complexity at fine timescales in the parietal and centro-temporal region. These outcomes indicate that two separate time pathways (corresponding to fine and coarse timescales) used to characterize rsEEG complexity (expressed by mMSE features) are beneficial for effective information processing.

ERP evidence for rapid within-trial adaptation of cognitive control during conflict resolution.

People often have to resolve many conflicts at the same time in their everyday lives. So far, the mechanisms of conflict resolution when multiple conflicts co-occur are not clear. This study examined the neurocognitive mechanisms of cognitive-control adaptation when two sources of conflict co-occur. To this aim, we measured event-related potentials in a task combining the Stroop conflict (the meaning and the color of a word differ) and the word-word conflict (two different words are presented). The word-word conflict was expected to tap the same stage of stimuli processing (i.e., semantics) and to modulate the magnitude of the Stroop conflict. Behavioral data showed that the word-word conflict facilitated the resolution of the Stroop conflict, which indicates the within-trial adaptation of cognitive control. ERP data showed two additive effects (the Stroop conflict and the word-word conflict) in the N450 time window, which suggests that at the neural level these two conflicts were processed in parallel (simultaneously and independently of each other). The N450 finding demonstrates that the control system flexibly and rapidly adapts to different types of conflict by modulating information processing in ways that individually address each source of conflict. Crucially, processing the conflicts in parallel substantially improved the efficiency of the control system. Overall, the study shows that the cognitive-control system can act as a collection of parallel but independent mechanisms; it thereby advances our understanding of goal-directed behavior.

Patterns of bilingual language use and response inhibition: A test of the adaptive control hypothesis.

Given prior studies that provided inconsistent results, there is an ongoing debate on the issue of whether bilingualism benefits cognitive control. We tested the Adaptive Control Hypothesis, according to which only the intense use of different languages in the same situation without mixing them in single utterances (called dual-language context) confers a bilingual advantage in response inhibition. In a large-scale correlational study, we attempted to circumvent several pitfalls of previous research on the bilingual advantage by testing a relatively large sample of participants and employing a more reliable and valid measurement of constructs (i.e., latent variable approach accompanied by Bayesian estimation). Our results do not support the Adaptive Control Hypothesis' prediction: the intensity of the dual-language context experience was unrelated to the efficiency of response inhibition in bilinguals. The results suggest that the Adaptive Control Hypothesis is not likely to account for the inconsistent results regarding the bilingual advantage hypothesis, at least in the case of the response-inhibition mechanism. At the same time, the study points to the problem of measuring the response-inhibition construct at the behavioral level. No evidence for a robust response-inhibition construct adds to the growing skepticism on this issue in the literature.

Susceptibility to distraction during analogical reasoning in schizophrenia.

Proportional analogies between four objects (e.g., a squirrel is to tree as a golden fish is to? aquarium) were examined in 30 schizophrenia patients and 30 healthy controls. Half of the problems included distracting response options: remote semantic associates (fishing rod) and perceptually similar salient distractors (shark). Although both patients and controls performed fairly accurately on the no-distraction analogies, patients' performance in the presence of distractors was distorted, suggesting deficits in attention and cognitive control affecting complex cognition. Finally, although education, fluid intelligence, and interference resolution strongly predicted distractibility in the control group, in the schizophrenia group susceptibility to distraction was unrelated to these markers of general cognitive ability, implying an idiosyncratic nature of reasoning distortions in schizophrenia.

Most evidence for the compensation account of cognitive training is unreliable.

Cognitive training and brain stimulation studies have suggested that human cognition, primarily working memory and attention control processes, can be enhanced. Some authors claim that gains (i.e., post-test minus pretest scores) from such interventions are unevenly distributed among people. The magnification account (expressed by the evangelical "who has will more be given") predicts that the largest gains will be shown by the most cognitively efficient people, who will also be most effective in exploiting interventions. In contrast, the compensation account ("who has will less be given") predicts that such people already perform at ceiling, so interventions will yield the largest gains in the least cognitively efficient people. Evidence for this latter account comes from reported negative correlations between the pretest and the training/stimulation gain. In this paper, with the use of mathematical derivations and simulation methods, we show that such correlations are pure statistical artifacts caused by the widely known methodological error called "regression to the mean". Unfortunately, more advanced methods, such as alternative measures, linear models, and control groups do not guarantee correct assessment of the compensation effect either. The only correct method is to use direct modeling of correlations between latent true measures and gain. As to date no training/stimulation study has correctly used this method to provide evidence in favor of the compensation account, we must conclude that most (if not all) of the evidence should be considered inconclusive.

Much ado about aha!: Insight problem solving is strongly related to working memory capacity and reasoning ability.

A battery comprising 4 fluid reasoning tests as well as 13 working memory (WM) tasks that involved storage, recall, updating, binding, and executive control, was applied to 318 adults in order to evaluate the true relationship of reasoning ability and WM capacity (WMC) to insight problem solving, measured using 40 verbal, spatial, math, matchstick, and remote associates problems (insight problems). WMC predicted 51.8% of variance in insight problem solving and virtually explained its almost isomorphic link to reasoning ability (84.6% of shared variance). The strong link between WMC and insight pertained generally to most WM tasks and insight problems, was identical for problems solved with and without reported insight, was linear throughout the ability levels, and was not mediated by age, motivation, anxiety, psychoticism, and openness to experience. In contrast to popular views on the sudden and holistic nature of insight, the solving of insight problems results primarily from typical operations carried out by the basic WM mechanisms that are responsible for the maintenance, retrieval, transformation, and control of information in the broad range of intellectual tasks (including fluid reasoning). Little above and beyond WM is unique about insight. (PsycINFO Database Record

Working memory facilitates insight instead of hindering it: Comment on DeCaro, Van Stockum, and Wieth (2016).

The "nothing-special" account of insight predicts positive correlations of insight problem solving and working memory capacity (WMC), whereas the "special-process" account expects no, or even negative, correlations. In the latter vein, DeCaro, Van Stockum Jr., and Wieth (2016) have recently reported weak negative WMC correlations with 2 constraint relaxation matchstick problems and 3 insight problems, and thus they claim that WM hinders insight. Here, we report on 3 studies that investigated WMC and various matchstick and classical problems (including 1 study that precisely replicated DeCaro et al.'s procedure). All 3 studies yielded moderate positive correlations of WMC with both the constraint relaxation and the classical problems. WMC explained 10% variance in problem solving, no matter what problems were used or how they were applied. Thus, DeCaro et al.'s claim that WM hinders insight is unwarranted. The opposite is true: WM facilitates insight. (PsycINFO Database Record

Gestalt Effects in Visual Working Memory.

Four experiments investigated whether conforming to Gestalt principles, well known to drive visual perception, also facilitates the active maintenance of information in visual working memory (VWM). We used the change detection task, which required the memorization of visual patterns composed of several shapes. We observed no effects of symmetry of visual patterns on VWM performance. However, there was a moderate positive effect when a particular shape that was probed matched the shape of the whole pattern (the whole-part similarity effect). Data support the models assuming that VWM encodes not only particular objects of the perceptual scene but also the spatial relations between them (the ensemble representation). The ensemble representation may prime objects similar to its shape and thereby boost access to them. In contrast, the null effect of symmetry relates the fact that this very feature of an ensemble does not yield any useful additional information for VWM.

Fluid Intelligence and the Cross-Frequency Coupling of Neuronal Oscillations.

Several existing theoretical models predict that the individual capacity of working memory and abstract reasoning (fluid intelligence) strongly depends on certain features of neuronal oscillations, especially their cross-frequency coupling. Empirical evidence supporting these predictions is still scarce, but it makes the future studies on oscillatory coupling a promising line of research that can uncover the physiological underpinnings of fluid intelligence. Cross-frequency coupling may serve as the optimal level of description of neurocognitive processes, integrating their genetic, structural, neurochemical, and bioelectrical underlying factors with explanations in terms of cognitive operations driven by neuronal oscillations.

ERP correlates of the conflict level in the multi-response Stroop task.

This EEG study (N=33) examined event-related potentials associated with conflict between activated responses in the Stroop task, in order to examine the conflict monitoring theory of cognitive control, which predicts the strength of exerted control to be proportional to the detected level of conflict. However, existing research manipulated the sole presence/absence of conflict, but not its exact level. Here, by using a modified color-word task that allowed multiple correct responses for target colors, as well as multiple incorrect responses for distractor words, we manipulated the level of conflict among activated responses (and not only its presence). We expected that a larger number of activated incorrect responses (i.e., a presumably higher conflict) would entail more pronounced conflict-related potentials. Indeed, two components of the N450 wave, parietal negativity and medial frontal negativity, were more negatively deflected when conflict was higher, than when it was lower, visibly responding to the level of conflict. Slow potential weakly responded to the sheer presence of conflict, but not to its level. These results can be plausibly explained by the conflict monitoring theory with a modified conflict evaluation formula, whereas they are at odds with several alternative theories of cognitive control.