Co-Representation In Joint Picture Naming Tasks

Joint Action refers to the action of two or more individuals who adjust their behavior in time or space to achieve a common goal.Co-representation is the key to successful joint action and refers to the sharing of the same referential object or event in the cognitive system of two or more individuals.Through co-representation,individuals can predict and coordinate their own actions with those of others to successfully complete joint tasks.Similarly,predicting the speech behaviors of others is crucial in interpersonal communication as a joint task.While previous research has found evidence of co-representation in joint picture naming tasks,recent studies have yielded inconsistent results regarding the level at which co-representation occurs.Some studies support actor-level co-representation,suggesting that individuals only represent who is responding in the current trial of the joint picture naming task.Other studies suggest task-level co-representation,indicating that individuals also represent the task of their partner(stimulus-response mapping)during the joint picture naming task.Importantly,previous research has only explored the neural mechanisms underlying joint picture naming tasks through behavioral or single-person EEG studies,which cannot provide a comprehensive understanding of the social brain mechanisms involved in joint picture naming tasks performed by multiple individuals.In recent years,numerous studies using hyper-scanning techniques and interbrain synchrony measures have investigated the social brain mechanisms underlying social tasks,with one hyper-scanning study indicating that interbrain synchrony is a critical index reflecting the establishment of co-representation mechanisms during joint tasks.This study explores the neural mechanisms underpinning joint picture naming tasks through three EEG experiments.Experiment 1 investigated whether individuals represent their partner during joint picture naming tasks and at what level of representation,using ERP and interbrain synchrony measures.Two participants sat side-by-side in front of a computer screen and completed a joint naming task.One participant was randomly assigned as the target participant and the other was their partner.We focused on the target participant’s data.The color frame surrounding each picture indicated whether the target(self-go),partner(partner-go),or neither participant(no-go)should respond.In the joint naming condition,both individuals made color judgments and named the pictures.In the single naming condition,only the target participant named the pictures,while the partner maintained attention without responding.Additionally,we manipulated the frequency of the picture names,with half being high-frequency words and half being low-frequency words.If there is a frequency effect in the partner-go condition but not in the single naming no-go condition,it suggests that the target participant simulated their partner’s lexical access process(i.e.,task co-representation).However,our ERP results showed similar frequency effects between the partner-go condition and the single naming no-go condition for the target participant.This suggests that the frequency effect in the partner-go condition was not caused by task co-representation.Importantly,our interbrain synchrony results showed significantly stronger Theta and Alpha band synchrony between the target participant and their partner in the joint naming partner-go and joint naming no-go conditions compared to the single naming condition,indicating action co-representation between them rather than task co-representation.Finally,behavioral results showed longer response times in the joint condition than in the single condition,suggesting that individuals required more cognitive processing,possibly due to action co-representation.In conclusion,we found evidence of co-representation during joint picture naming tasks,but not task co-representation.Joint naming tasks may involve other brain mechanisms that allow individuals to access lexical information for pictures they do not name themselves.Experiment 2 and Experiment 3 investigated why target participants still exhibited the ERP frequency effect in unnamed picture and further verified whether there was a co-representation of the task behind the joint picture naming task.Experiment 2 only included single-person naming conditions,and only one participant completed the go/no-go task of picture naming.The color rectangular frame around the image indicated whether a naming response was required.In Experiment 3,participants were presented with the same pictures but were only required to maintain concentration without making any responses.The ERP frequency effect was still observed in the no-go condition of Experiment 2.No frequency effect was found in Experiment 3.These results suggest that individuals’ ERPs are modulated by the picture frequency regardless of whether the image belongs to oneself,a partner,or no one,only when they are in a task context requiring naming responses(Experiment 1 & Experiment 2).When individuals are in a task context without naming responses(Experiment 3),their ERPs are not modulated by picture frequency.We believe that the phenomenon where individuals’ ERPs are modulated by picture frequency in response to unnamed images is possibly due to the individual’s internal language triggered by the naming task context.Specifically,in the naming task context,individuals spontaneously generate verbal labels for unnamed images,resulting in ERPs that are modulated by the picture frequency even when naming is not required.Based on the results of the three experiments,we conclude that individuals may share a co-representation of their partner in joint picture naming tasks but may not have a co-representation at the task level.Furthermore,there may be an internal language mechanism triggered by the naming task context that leads individuals to name unnamed images in their minds,even when naming is not required.