Enhancing task-demands disrupts learning but enhances transfer gains in short-term task-switching training.

Content variability was previously suggested to promote stronger learning effects in cognitive training whereas less variability incurred transfer costs (Sabah et al. Psychological Research, https://doi.org/10.1007/s00426-018-1006-7 , 2018). Here, we expanded these findings by additionally examining the role of learners' control in short-term task-switching training by comparing voluntary task-switching to a yoked control forced task-switching condition. To this end, four training conditions were compared: (1) forced fixed content, (2) voluntary fixed content, (3) forced varied content, and (3) voluntary varied content. To further enhance task demands, bivalent stimuli were used during training. Participants completed baseline assessment commencing with task-switching and verbal fluency blocks, followed by seven training blocks and last by task-switching (near transfer) and verbal fluency (far transfer) blocks, respectively. For the baseline and transfer task-switching blocks, we used the exact same baseline and first transfer block from Sabah et al. (Psychological Research, https://doi.org/10.1007/s00426-018-1006-7 , 2018), employing univalent stimuli and alternating-runs task sequence. Our results pointed again to the contribution of content variability to task-switching performance. No indications for far transfer were observed. Allowing for learners' control was not found to produce additional transfer gains beyond content variability. A between-study comparison suggests that enhanced task demands, by means of bivalency, promoted higher transfer gains in the current study when compared to Sabah et al. (Psychological Research, https://doi.org/10.1007/s00426-018-1006-7 , 2018). Taken together, the current results provide further evidence to the beneficial impact of variability on training outcomes. The lack of modulatory effect for learners' control is discussed in relation to possible methodological limitations.

Challenging voices: Mixed evidence for context-specific control adjustments in the auditory domain.

The flexible adjustment to changing demands is an astonishing human ability. One related phenomenon is the context-specific proportion congruency (CSPC) effect. Regarding response conflict, the CSPC refers to reduced response interference in contexts with a high conflict proportion as opposed to contexts with a low conflict proportion. Derived from previous research showing CSPCs in the visual domain, we here aim to investigate whether human voices (male vs. female) as auditory contexts trigger control adjustments. To this end, we used a numerical judgement task with number words spoken by a male or female voice. We created response conflict by presenting the words either to the left or right ear (Experiment 1), and we created different levels of processing fluency by presenting them clearly or with background noise (Experiment 2). For a given participant, either the female or the male voice was associated with a high proportion of incongruent/disfluent trials and a low proportion of congruent/fluent trials, respectively. Extending previous findings from the visual modality, we found that the frequency of challenging information within one auditory context (i.e., the voice) can lead to typical CSPC patterns. In two further experiments, using frequency biased and unbiased items, we found evidence for the contribution of associative learning. Limitations of context control associations will be discussed.

When less is more: costs and benefits of varied vs. fixed content and structure in short-term task switching training.

Training variability has been brought forward as one possible moderator for wider scale transfer effects in cognitive training. However, little is known about which aspects of task variability are important for optimizing training outcomes. This study systematically examined the impact of variability in the different task components on outcome measures, here manipulating content (whether the task stimuli remained fixed or changed between blocks) and the deeper structural task configuration (task sequence: whether the task sequence was fixed or random). Short-term task switching training was implemented with one of four training variability conditions: fixed content\fixed structure; fixed content\ random structure; varied content\fixed structure and varied content\varied structure. The experiment consisted of a baseline block, seven training blocks (learning phase), followed by two transfer blocks, one with fixed and one with random task structure, respectively. In the learning phase, more rapid training gains were observed in the fixed content as compared to varied content. Interestingly, training with fixed content resulted in a trend for costs when transferred to a novel task switching context. In contrast, moderate transfer gains were noted in the varied content condition, manifested specifically on switch trials. These results suggest that task (content) variability is one of the means to improve positive transfer and avoid negative transfer. Additionally, and in agreement with the wide literature on training, this finding suggests that conditions that prevent training gains are in fact beneficial for learning generalization.

The Multimodal Go-Nogo Simon Effect: Signifying the Relevance of Stimulus Features in the Go-Nogo Simon Paradigm Impacts Event Representations and Task Performance.

Numerous studies have shown that stimulus-response-compatibility (SRC) effects in the go-nogo version of the Simon task can be elicited as a result of performing the task together with another human or non-human agent (e.g., a Japanese-waving-cat, a working-clock, or a ticking-metronome). A parsimonious explanation for both social and non-social SRC effects is that highlighting the spatial significance of alternative (non-/social) action events makes action selection more difficult. This holds even when action events are task-irrelevant. Recent findings, however, suggest that this explanation holds only for cases of a modality correspondence between the Simon task as such (i.e., auditory or visual) and the alternative (non-/social) action event that needs to be discriminated. However, based on the fact that perception and action are represented by the same kind of codes, an event that makes the go-nogo decision more challenging should impact go-nogo Simon task performance. To tackle this issue, the present study tested if alternative stimulus events that come from a different sensory modality do impact SRC effects in the go-nogo version of the Simon task. This was tested in the presence and absence of alternative action events of a human co-actor. In a multimodal (auditory-visual) go-nogo Simon paradigm, participants responded to their assigned stimulus - e.g., a single auditory stimulus while ignoring the alternative visual stimulus or vice versa - in the presence or absence of a human co-actor (i.e., joint and single go-nogo condition). Results showed reliable SRCs in both, single and joint go-nogo Simon task conditions independent of the modality participants had to respond to. Although a correspondence between stimulus material and attention-grabbing event might be an efficient condition for SRCs to emerge, the driving force underlying the emergence of SRCs rather appears to be whether the attentional focus prevents or facilitates alternative events to be integrated. Thus, under task conditions in which the attentional focus is sufficiently broad to enable the integration and thus cognitive representation of alternative events, go-nogo decisions become more difficult, resulting in reliable SRCs in single and joint go-nogo Simon tasks.

RETRACTED: Auditory (dis-)fluency triggers sequential processing adjustments.

An increasing amount of studies indicates that experiencing increased task demands, triggered for example by conflicting stimulus features or low perceptual fluency, lead to processing adjustments. While these demand-triggered processing adjustments have been shown for different paradigms (e.g., response conflict tasks, perceptual disfluency, task switching, dual tasking), most of them are restricted to the visual modality. The present study investigated as to whether the challenge to understand speech signals in normal-hearing subjects would also lead to sequential processing adjustments if the processing fluency of the respective auditory signals changes from trial to trial. To that end, we used spoken number words (one to nine) that were either presented with high (clean speech) or low perceptual fluency (i.e., vocoded speech as used in cochlear implants-Experiment 1; speech embedded in multi-speaker babble noise as typically found in bars-Experiment 2). Participants had to judge the spoken number words as smaller or larger than five. Results show that the fluency effect (performance difference between high and low perceptual fluency) in both experiments was smaller following disfluent words. Thus, if it's hard to understand, you try harder.

Are You Keeping an Eye on Me? The Influence of Competition and Cooperation on Joint Simon Task Performance.

Social interaction plays an important role in human life. While there are instances that require cooperation, there are others that force people to compete rather than to cooperate, in order to achieve certain goals. A key question is how the deployment of attention differs between cooperative and competitive situation; however, empirical investigations have yielded inconsistent results. By manipulating the (in-)dependence of individuals via performance-contingent incentives, in a visual go-nogo Simon task the current study aimed at improving our understanding of complementary task performance in a joint action context. In the independent condition each participant received what s/he achieves; in the cooperative condition each participant received the half of what both achieved, and in the competitive condition participants were instructed that the winner takes it all. Extending previous findings, we found sequential processing adjustments of the Simon effect as a function of the interdependency (i.e., competition, cooperation) and transition between (i.e., go-nogo requirements) interacting individuals. While sequential processing adjustments of the Simon effect in both the competition and cooperation condition were unaffected when alternating between responsible actors (i.e., nogo-go transition), sequential processing adjustments were enlarged under competition for repeating responsibilities of one and the same actor (i.e., go-go transitions). In other words, the prospect of performance-contingent reward in a competitive context exclusively impacts flexible behavioral adjustments of one's own actions. Rather than fostering the consideration and differentiation of the other actor, pushing one's own performance to the limit appears to be the suitable strategy in competitive instances of complementary tasks. Therefore, people keep their eyes on themselves when aiming at beating a co-actor and emerging as the winner.

IPL-M1 interaction shapes pre-reflective social differentiation in the human action system: new insights from TBS and TMS combined.

The conscious experience of being the author of our own actions is thought to be grounded in pre-reflective and low-level sensorimotor representations of the self as different from the other. It has been suggested that the inferior parietal lobe (IPL) is generally involved in self-other differentiation processes and in providing an explicit sense of action authorship. However, direct evidence for its causal and functional role in distinguishing self-related and other-related sensorimotor representations is lacking. The current study employed theta-burst stimulation (TBS) to condition left IPL's activity before a social version of the rubber hand illusion led participants to illusorily attribute observed finger movements to their own body. We recorded motor evoked potentials to single-pulse transcranial magnetic stimulation over the primary motor cortex (M1) as proxies of action authorship during action observation. The results showed that in a control condition (intermediate TBS over the left IPL) others' actions facilitated whereas self-attributed movements inhibited the motor system. Critically, continuous TBS disrupted this mismatch between self and other representations. This outcome provides direct evidence for the IPL's role in providing fundamental authorship signals for social differentiation in the human action system.

Self-perception beyond the body: the role of past agency.

Technological progress provides us with an increasing variety of devices that now mediate what previously has been achieved by social face-to-face interaction. Here, we investigate whether this leads to the incorporation of such devices into representations of our body. Using explicit (body ownership questionnaire) and implicit (proprioceptive drift rate) measures together with a synchronous/asynchronous stroking technique, we show that people have an increased tendency to integrate non-corporeal objects into their body after synchronous stroking. Explicit measures of body ownership show that people had greater average scores in the synchronous condition as compared to the asynchronous condition for all objects that we tested (computer mouse, rubber hand, smart phone, and a wooden block). However, our implicit measure of body ownership showed a numerically larger proprioceptive drift for a rubber hand than for a computer mouse, numerically comparable ownership measures for a smart phone and a rubber hand, and a significantly stronger proprioceptive drift for a smart phone than for a wooden block. These findings suggest that direct, subjective measures and indirect, objective measures of body ownership are based on different kinds of information; the latter might be more sensitive to objects for which we recall past agency based on our history of personal experiences with these objects. Taken altogether, our observations support the idea that the perceived bodily self is rather flexible and is likely to emerge through multisensory integration and top-down expectations of agency.

Is Handwriting Performance Affected by the Writing Surface? Comparing Preschoolers', Second Graders', and Adults' Writing Performance on a Tablet vs. Paper.

Due to their multifunctionality, tablets offer tremendous advantages for research on handwriting dynamics or for interactive use of learning apps in schools. Further, the widespread use of tablet computers has had a great impact on handwriting in the current generation. But, is it advisable to teach how to write and to assess handwriting in pre- and primary schoolchildren on tablets rather than on paper? Since handwriting is not automatized before the age of 10 years, children's handwriting movements require graphomotor and visual feedback as well as permanent control of movement execution during handwriting. Modifications in writing conditions, for instance the smoother writing surface of a tablet, might influence handwriting performance in general and in particular those of non-automatized beginning writers. In order to investigate how handwriting performance is affected by a difference in friction of the writing surface, we recruited three groups with varying levels of handwriting automaticity: 25 preschoolers, 27 second graders, and 25 adults. We administered three tasks measuring graphomotor abilities, visuomotor abilities, and handwriting performance (only second graders and adults). We evaluated two aspects of handwriting performance: the handwriting quality with a visual score and the handwriting dynamics using online handwriting measures [e.g., writing duration, writing velocity, strokes and number of inversions in velocity (NIV)]. In particular, NIVs which describe the number of velocity peaks during handwriting are directly related to the level of handwriting automaticity. In general, we found differences between writing on paper compared to the tablet. These differences were partly task-dependent. The comparison between tablet and paper revealed a faster writing velocity for all groups and all tasks on the tablet which indicates that all participants-even the experienced writers-were influenced by the lower friction of the tablet surface. Our results for the group-comparison show advancing levels in handwriting automaticity from preschoolers to second graders to adults, which confirms that our method depicts handwriting performance in groups with varying degrees of handwriting automaticity. We conclude that the smoother tablet surface requires additional control of handwriting movements and therefore might present an additional challenge for learners of handwriting.

Adapting to the surface: A comparison of handwriting measures when writing on a tablet computer and on paper.

Our study addresses the following research questions: Are there differences between handwriting movements on paper and on a tablet computer? Can experienced writers, such as most adults, adapt their graphomotor execution during writing to a rather unfamiliar surface for instance a tablet computer? We examined the handwriting performance of adults in three tasks with different complexity: (a) graphomotor abilities, (b) visuomotor abilities and (c) handwriting. Each participant performed each task twice, once on paper and once on a tablet computer with a pen. We tested 25 participants by measuring their writing duration, in air time, number of pen lifts, writing velocity and number of inversions in velocity. The data were analyzed using linear mixed-effects modeling with repeated measures. Our results reveal differences between writing on paper and on a tablet computer which were partly task-dependent. Our findings also show that participants were able to adapt their graphomotor execution to the smoother surface of the tablet computer during the tasks.

A role of goals for social inhibition of return?

The social inhibition of return (sIOR) effect refers to the finding that response initiation times are longer if a movement is executed to a location where another person has responded to just before. Previous studies have examined the influence of the goal of the action on sIOR. In these studies, however, the movement endpoint and to-be-attained goal (e.g., touching/pressing a response key) were at the same spatial location. In the present two experiments, we disentangled movement endpoint and goal's identity and locations by means of introducing action effects that followed directly from a movement. Similar methods were previously shown powerful enough to clearly show the importance of action goals for other phenomena-a finding consistent with effect-based theories of action control, such as the ideomotor theory. The results of the present study revealed that sIOR was shaped by the movement endpoint location, not the goal's identity or location. That is, in both experiments, an sIOR effect was observed, but the magnitude of the sIOR effect was not modulated by repetitions/switches of goals or their locations. Thus, results indicate that goals play a negligible role in the emergence of the sIOR and, consequently, highlight the importance of action observation for the emergence of the sIOR effect.

Referential coding does not rely on location features: Evidence for a nonspatial joint Simon effect.

The joint Simon effect (JSE) shows that the presence of another agent can change one's representation of one's task and/or action. According to the spatial response coding approach, this is because another person in one's peri-personal space automatically induces the spatial coding of one's own action, which in turn invites spatial stimulus-response priming. According to the referential coding approach, the presence of another person or event creates response conflict, which the actor is assumed to solve by emphasizing response features that discriminate between one's own response and that of the other. The 2 approaches often make the same predictions, but the spatial response coding approach considers spatial location as the only dimension that can drive response coding, whereas the referential coding approach allows for other dimensions as well. To compare these approaches, the authors ran 2 experiments to see whether a nonspatial JSE can be demonstrated. Participants responded to the geometrical shape of a central colored stimulus by pressing a left or right button, while wearing gloves of the same or different color as the stimuli. Participants performed the task individually, either by responding to either stimulus shapes (Experiment 1) or by responding to only 1 of the 2 shapes (Experiment 2), and in the presence of a coactor. Congruence between stimulus and glove color affected performance in the 2-choice and the joint tasks but not in the individual go/no-go task. This demonstration of a nonspatial JSE is inconsistent with the spatial response coding approach but supports the referential coding approach.

The joint Simon effect: a review and theoretical integration.

The social or joint Simon effect has been developed to investigate how and to what extent people mentally represent their own and other persons' action/task and how these cognitive representations influence an individual's own behavior when interacting with another person. Here, we provide a review of the available evidence and theoretical frameworks. Based on this review, we suggest a comprehensive theory that integrates aspects of earlier approaches-the Referential Coding Account. This account provides an alternative to the social interpretation of the (joint) go-nogo Simon effect (aka the social Simon effect) and is able to integrate seemingly opposite findings on joint action.

The joint Simon effect depends on perceived agency, but not intentionality, of the alternative action.

A co-actor's intentionality has been suggested to be a key modulating factor for joint action effects like the joint Simon effect (JSE). However, in previous studies intentionality has often been confounded with agency defined as perceiving the initiator of an action as being the causal source of the action. The aim of the present study was to disentangle the role of agency and intentionality as modulating factors of the JSE. In Experiment 1, participants performed a joint go/nogo Simon task next to a co-actor who either intentionally controlled a response button with own finger movements (agency+/intentionality+) or who passively placed the hand on a response button that moved up and down on its own as triggered by computer signals (agency-/intentionality-). In Experiment 2, we included a condition in which participants believed that the co-actor intentionally controlled the response button with a Brain-Computer Interface (BCI) while placing the response finger clearly besides the response button, so that the causal relationship between agent and action effect was perceptually disrupted (agency-/intentionality+). As a control condition, the response button was computer controlled while the co-actor placed the response finger besides the response button (agency-/intentionality-). Experiment 1 showed that the JSE is present with an intentional co-actor and causality between co-actor and action effect, but absent with an unintentional co-actor and a lack of causality between co-actor and action effect. Experiment 2 showed that the JSE is absent with an intentional co-actor, but no causality between co-actor and action effect. Our findings indicate an important role of the co-actor's agency for the JSE. They also suggest that the attribution of agency has a strong perceptual basis.

The joint flanker effect: less social than previously thought.

Research on joint action has been taken to suggest that actors automatically co-represent the tasks and/or actions of co-actors. However, recent findings on the joint Simon effect have provided evidence for a nonsocial account, which renders automatic co-representation unlikely. In the present study, we aimed to test whether a nonsocial account is also feasible for the joint version of the flanker task. In particular, we manipulated the social nature of the "co-actor" who could be another human or a Japanese waving cat. Contrary to the social interpretation of the joint flanker effect, the results demonstrated a "joint" flanker effect, irrespective of whether participants shared the task with another person or with the Japanese waving cat.

Joint response-effect compatibility.

When performing jointly on a task, human agents are assumed to represent their coactor's share of this task, and research in various joint action paradigms has focused on representing the coactor's stimulus-response assignments. Here we show that the response-effect (R-E) contingencies exploited by a coactor also affect performance, and thus might be represented as if they were used by oneself. Participants performed an R-E compatibility task, with keypresses producing spatially compatible or incompatible action effects. We did not observe any R-E compatibility effects when the task was performed in isolation (individual go-no-go). By contrast, small but reliable R-E compatibility effects emerged when the same task was performed in a joint setting. These results indicate that the knowledge of a coactor's R-E contingencies can influence whether self-produced action effects are used for one's own motor control.

Keys and seats: Spatial response coding underlying the joint spatial compatibility effect.

Spatial compatibility effects (SCEs) are typically observed when participants have to execute spatially defined responses to nonspatial stimulus features (e.g., the color red or green) that randomly appear to the left and the right. Whereas a spatial correspondence of stimulus and response features facilitates response execution, a noncorrespondence impairs task performance. Interestingly, the SCE is drastically reduced when a single participant responds to one stimulus feature (e.g., green) by operating only one response key (individual go/no-go task), whereas a full-blown SCE is observed when the task is distributed between two participants (joint go/no-go task). This joint SCE (a.k.a. the social Simon effect) has previously been explained by action/task co-representation, whereas alternative accounts ascribe joint SCEs to spatial components inherent in joint go/no-go tasks that allow participants to code their responses spatially. Although increasing evidence supports the idea that spatial rather than social aspects are responsible for joint SCEs emerging, it is still unclear to which component(s) the spatial coding refers to: the spatial orientation of response keys, the spatial orientation of responding agents, or both. By varying the spatial orientation of the responding agents (Exp. 1) and of the response keys (Exp. 2), independent of the spatial orientation of the stimuli, in the present study we found joint SCEs only when both the seating and the response key alignment matched the stimulus alignment. These results provide evidence that spatial response coding refers not only to the response key arrangement, but also to the-often neglected-spatial orientation of the responding agents.

Visual experience determines the use of external reference frames in joint action control.

Vision plays a crucial role in human interaction by facilitating the coordination of one's own actions with those of others in space and time. While previous findings have demonstrated that vision determines the default use of reference frames, little is known about the role of visual experience in coding action-space during joint action. Here, we tested if and how visual experience influences the use of reference frames in joint action control. Dyads of congenitally-blind, blindfolded-sighted, and seeing individuals took part in an auditory version of the social Simon task, which required each participant to respond to one of two sounds presented to the left or right of both participants. To disentangle the contribution of external-agent-based and response-based-reference frames during joint action, participants performed the task with their respective response (right) hands uncrossed or crossed over one another. Although the location of the auditory stimulus was completely task-irrelevant, participants responded overall faster when the stimulus location spatially corresponded to the required response side than when they were spatially non-corresponding: a phenomenon known as the social Simon effect (SSE). In sighted participants, the SSE occurred irrespective of whether hands were crossed or uncrossed, suggesting the use of external, response-based reference frames. Congenitally-blind participants also showed an SSE, but only with uncrossed hands. We argue that congenitally-blind people use both agent-based and response-based reference frames resulting in conflicting spatial information when hands are crossed and, thus, canceling out the SSE. These results imply that joint action control functions on the basis of external reference frames independent of the presence or (transient/permanent) absence of vision. However, the type of external reference frames used for organizing motor control in joint action seems to be determined by visual experience.