Guenther Knoblich

Is it really my turn? An event-related fMRI study of task sharing

Abstract Acting together with others is a fundamental human ability. This raises the possibility that we take others’ actions into account whenever somebody acts around us. Event-related fMRI was used to identify brain regions responsive to changes in cognitive processing when one and the same go–nogo task is performed alone or together with a co-actor performing a complementary task. Reaction times showed that participants integrated the potential action of their co-actor in their own action planning. Increased activation in ventral premotor cortex was found when participants acted upon stimuli referring to their own action alternative, but only when their partner performed a complementary task. This suggests that knowing about the potential actions of a partner increases the relevance of stimuli referring to oneself. Acting in the presence of a co-actor was also associated with increased orbitofrontal activation, indicating that participants monitored their performance more closely to make sure it really was their turn. These results suggest that our default mode is to interact with others.

Altered sense of agency in schizophrenia and the putative psychotic prodrome

The mechanisms underlying distortions in sense of agency, i.e. the experience of controlling ones own actions and their consequences, in schizophrenia are not fully understood and have barely been investigated in patients classified as being in a putative psychotic prodrome. This study aims to expound the contribution of early and late illness-related processes. Thirty schizophrenia patients, 30 putatively prodromal patients and 30 healthy controls were instructed to reproduce a computer-generated series of drum sounds on a drum pad. While tapping, subjects heard either their self-produced tones or a computer-controlled reproduction of the drum tone series that used either exactly the same, an accelerated or decelerated tempo. Subjects had to determine the source of agency. Results show similar significant impairments in assigning the source of agency under ambiguous conditions in schizophrenia and putatively prodromal patients and an exaggerated self-attribution bias, both of which were significantly correlated with increased (ego-)psychopathology. Patient groups, however, benefited significantly more than controls from additional sensorimotor cues to agency. Sensorimotor input seems to be a compensatory mechanism involved in correctly attributing agency. We deduce that altered awareness of agency may hold promise as an additional risk factor for psychosis.

The role of motor simulation in action perception: a neuropsychological case study

Research on embodied cognition stresses that bodily and motor processes constrain how we perceive others. Regarding action perception the most prominent hypothesis is that observed actions are matched to the observer’s own motor representations. Previous findings demonstrate that the motor laws that constrain one’s performance also constrain one’s perception of others’ actions. The present neuropsychological case study asked whether neurological impairments affect a person’s performance and action perception in the same way. The results showed that patient DS, who suffers from a frontal brain lesion, not only ignored target size when performing movements but also when asked to judge whether others can perform the same movements. In other words DS showed the same violation of Fitts’s law when performing and observing actions. These results further support the assumption of close perception action links and the assumption that these links recruit predictive mechanisms residing in the motor system.

Your words are my words: Effects of acting together on encoding

Social influences on action and memory are well established. However, it is unknown how acting together affects the incidental encoding of information. The present study asked whether coactors encode information that is relevant to a partners task, but irrelevant to their own task. In Experiment 1, participants performed a categorization task alone and together, followed by a surprise free recall test where they were asked to recall items from the categorization task. Recall was better not only for items that participants had responded to themselves, but also for items that their coactor had responded to, than for items that had not required a response. The same results were found in Experiment 2, even though financial incentives motivated participants to only encode words they had responded to themselves. Together, the findings suggest that performing tasks together can modulate how information relevant to coactors is processed. Shared task representations may act as a vehicle for establishing shared memories.

The sense of agency during skill learning in individuals and dyads

The sense of agency has received much attention in the context of individual action but not in the context of joint action. We investigated how the sense of agency developed during individual and dyadic performance while people learned a haptic coordination task. The sense of agency increased with better performance in all groups. Individuals and dyads showed a differential sense of agency after initial task learning, with dyads showing a minimal increase. The sense of agency depended on the context in which the task was first learnt, as transfer from joint to individual performance resulted in an illusory boost in the sense of agency. Whereas the quality of performance related to the sense of agency, the generated forces to achieve the task did not. Our findings are consistent with a predictive model account at the perceptual level, such that the sense of agency relies most strongly on sharable perceptual information.

The role of chunk tightness and chunk familiarity in problem solving: Evidence from ERPs and fMRI

Multiple factors of task difficulty keep problem solvers from finding the crucial thinking steps required to solve insight problems. In this study, we distinguished two difficulty factors, chunk familiarity and chunk tightness, and investigated their effects on chunk decomposition—a specific type of insight that depends on the process of breaking up perceptual patterns or chunks into elements so that they can be reorganized to form a new meaning. Subjects solved problems that required decomposing Chinese characters that differed in chunk familiarity and chunk tightness. Brain activity was recorded using the electroencephalogram and functional magnetic resonance imaging. The results showed that chunk familiarity could be overcome through an inhibition of familiar meanings, whereas overcoming chunk tightness required visual‐spatial processing. Furthermore, chunk familiarity posed an additional difficulty when chunk tightness was high. This result demonstrates that the difficulty sources in a problem do not always simply add up. Rather, the difficulty of a problem can reside in the interaction of particular sources of difficulty. Hum Brain Mapp, 2013.

How perceptual processes help to generate new meaning: An EEG study of chunk decomposition in Chinese characters

Chunk decomposition has been regarded as an important process in problem solving that helps problem solvers to generate new solution paths through changing inappropriate problem representations. We studied the neural bases of chunk decomposition in Chinese characters using the electroencephalogram (EEG). Participants decomposed Chinese characters either at the level of radicals or at the level of strokes to generate new target characters with a different meaning. We hypothesized that decomposition at the stroke level would require a more fundamental change in the problem representation that should involve differences in basic visual processing. To test this hypothesis, we compared the alpha rhythm (8-13 Hz) over parietal-occipital regions between the two different conditions. The regrouping of tight chunks (stroke level) exhibited a stronger alpha activation than the regrouping of loose chunks approximately 500 ms prior to response. Thus visual areas were less active during the decomposition of tight chunks. Together with a previous fMRI study the results provide convincing evidence that attenuation of early visual information is required to generate new meaning.

EEG correlates of Fitts’s law during preparation for action

Humans’ inability to move fast and accurately at the same time is expressed in Fitts’s law. It states that the movement time between targets depends on the index of difficulty, which is a function of the target width and the inter-target distance. The present study investigated the electrophysiological correlates of Fitts’s law during action planning using high-density electroencephalography. Movement times were scaled according to Fitts’s law, indicating that participants could not overcome the speed–accuracy trade-off during a 1-s preparation period. Importantly, the index of difficulty of the planned movement correlated linearly with the amplitudes of the cognitive N2 and P3b components, which developed during the planning period over parieto-occipital areas. These results suggest that the difficulty of a movement during action planning is represented at a level where perceptual information about the difficulty of the ensuing action is linked to motor programming of the required movement.

Scaling up perception-action links: Evidence from synchronization with individual and joint action.

How do we map joint actions we participate in onto joint actions we observe others performing, such as when a couple dancing tango observes another couple dancing tango? We investigated this question using a task in which participants were instructed to perform individual or joint movements in synchrony with individual or joint movements observed on a computer screen. The observed movements started slowly and then continuously increased in tempo (from 1.75 Hz to 3 Hz). The results showed that, with regard to spatial parameters, joint performance was more accurate when observing joint action than when observing individual action (Experiments 1, 1a, and 1b). Individual performance was more accurate when observing individual action than when observing joint action (Experiments 3 and 4). There were no systematic differences with regard to timing parameters. These results suggest that mechanisms of temporal coordination may be less susceptible to differences between individual and joint action than mechanisms of spatial matching.

Cognitive Ethology for humans: Inconvenient truth or attentional deficit?

We discuss Kingstone et al.s target article in the light of emerging work on cognitive ethology.