Sukhvinder S. Obhi

Resonating with Others: The Effects of Self-Construal Type on Motor Cortical Output

“Self-construal” refers to how individuals view and make meaning of the self, and at least two subtypes have been identified. Interdependent self-construal is a view of the self that includes relationships with others, and independent self-construal is a view of the self that does not include relations with others. It has been suggested that priming these two types of self-construal affects the cognitive processing style that an individual adopts, especially with regard to context sensitivity. Specifically, an interdependent self-construal is thought to promote attention to others and social context to a greater degree than an independent self-construal. To investigate this assertion, we elicited motor-evoked potentials with transcranial magnetic stimulation during an action observation task in which human participants were presented with either interdependent or independent self-construal prime words. Priming interdependent self-construal increased motor cortical output whereas priming independent self-construal did not, compared with a no-priming baseline condition. These effects, likely mediated by changes in the mirror system, essentially tune the individual to, or shield the individual from, social input. Interestingly, the pattern of these self-construal-induced changes in the motor system corroborates with previously observed self-construal effects on overt behavioral mimicry in social settings, and as such, our results provide strong evidence that motor resonance likely mediates nonconscious mimicry in social settings. Finally, these self-construal effects may lead to the development of interventions for disorders of deficient or excessive social influence, like certain autism spectrum and compulsive imitative disorders.

Social Interaction Enhances Motor Resonance for Observed Human Actions

Understanding the neural basis of social behavior has become an important goal for cognitive neuroscience and a key aim is to link neural processes observed in the laboratory to more naturalistic social behaviors in real-world contexts. Although it is accepted that mirror mechanisms contribute to the occurrence of motor resonance (MR) and are common to action execution, observation, and imitation, questions remain about mirror (and MR) involvement in real social behavior and in processing nonhuman actions. To determine whether social interaction primes the MR system, groups of participants engaged or did not engage in a social interaction before observing human or robotic actions. During observation, MR was assessed via motor-evoked potentials elicited with transcranial magnetic stimulation. Compared with participants who did not engage in a prior social interaction, participants who engaged in the social interaction showed a significant increase in MR for human actions. In contrast, social interaction did not increase MR for robot actions. Thus, naturalistic social interaction and laboratory action observation tasks appear to involve common MR mechanisms, and recent experience tunes the system to particular agent types.

Automatic imitation is reduced in narcissists.

Narcissism is a personality trait that has been extensively studied in normal populations. Individuals high on subclinical narcissism tend to display an excessive self-focus and reduced concern for others. Does their disregard of others have roots in low-level processes of social perception? We investigated whether narcissism is related to the automatic imitation of observed actions. In the automatic imitation task, participants make cued actions in the presence of action videos displaying congruent or incongruent actions. The difference in response times and accuracy between congruent and incongruent trials (i.e., the interference effect) is a behavioral index of motor resonance in the brain-a process whereby observed actions activate matching motor representations in the observer. We found narcissism to be negatively related to interference in the automatic imitation task, such that high narcissism is associated with reduced imitation. Thus, levels of narcissism predict differences in the tendency to automatically resonate with others, and the pattern of data we observe suggests that a key difference is that high narcissists possess an improved ability to suppress automatic imitation when such imitation would be detrimental to task performance. To the extent that motor resonance is a product of a human mirror system, our data constitute evidence for a link between narcissistic tendencies and mirror system functioning.

The relative effects of external spatial and motoric factors on the bimanual coordination of discrete movements

The ability to coordinate the two hands effectively is a fundamental requirement for many everyday tasks. To investigate how bimanual coordination is achieved we asked subjects to perform discrete bimanual key-press responses under conditions in which the motoric (i.e., muscles employed) and external spatial (i.e., direction of movement in external space) relationships between the actions of the left and right index fingers were systematically varied. Subjects made simultaneous right and left index finger key-presses in response to an auditory tone. The right finger always made downward flexion movements whilst the left finger either flexed in a downward/upward direction, or extended in a downward/upward direction. Unimanual control trials of each movement type for both hands were also performed. Reaction times for each hand (RTs) and the inter-response interval (IRI) were recorded . Right hand RTs were significantly affected only when the left finger performed motorically different actions, but were unaffected by the external spatial direction in which the left hand’s actions were made. The IRI results followed a similar pattern with the worst coordination (highest IRI) occurring when the left finger performed different motor actions to the right finger regardless of the direction of the left hand movement. In contrast to other recent results from experiments examining oscillatory tasks (e.g., Mechsner et al. 2001), our results suggest that in discrete tasks there is a dominance of the motor relationship between the hands over the external spatial relationship.