1. Incompatible associations
Social Simon Effect: Co-Representation or Social Facilitation?
Karen Davranche, Laurence Carbonnell, Clément Belletier, Frank Vidal, Thierry Hasbroucq & Pascal Huguet Aix-Marseille Université & CNRS, France
Introduction
In the individual Go/Nogo task (Figure 2C), there is only one possible response. If the participant were seating on the left side, the response is given using the left response key with the left hand. When participant performed the joint Go/Nogo task (Figure 2A), each co-actor did exactly the same task than during the individual Go/Nogo task (Figure 2C). They sat on the same side, replied to the lit of the same colour and pressed the same response key with the same hand.
Results
Simon Effect
In the classical version of the Simon task (Figure 2B) participants are required to respond, as quickly and accurately, according to the color of the stimulus and inhibit the spatial location of the same stimulus. Reaction time (RT) is usually reported to be shorter when relevant and irrelevant information correspond to the same response than when they are mapped to different responses. See Figure 1. The difference between the RT during the incompatible and compatible associations is called the Simon effect.
“Micro” Simon Effect
When participants perform an individual Go/NoGo task (Figure 2C), a unique effector is involved and only one possible response. No effect or a “micro” Simon effect are generally reported.
Social Simon Effect (SSE)
The social Simon effect occurs when two participants performed a Joint Go/NoGo task (Figure 2A). Despite the fact that co-actors respond to only one of the two stimulus, RT performances are worse for contralateral than for ipsilateral trials.
As predicted from social facilitation theory, the benefit was larger for IPS trials than for CNT trials. Joint-action induced a larger facilitation on IPS trials (joint: 301ms vs. individual: 321ms) than on CNT trials (joint: 312ms vs. individual: 326ms) (F(1,36) = 15.48, p <.001).
The electromyographic (EMG) activity of the agonist muscle involved in the task was recorded bipolarly from the flexor pollicis brevis by surface Ag/AgCl electrodes (6mm diameter) (BIOSEMI Active-Two electrodes, Amsterdam). (Figure 3).
Figure 5. Reaction time (in milliseconds) in joint Go/Nogo and individual Go/Nogo tasks, as function of the side location (ipsilateral, IPS vs. contralateral, CNT) of the trial.
Compatible associations
Incompatible associations
This social facilitation effect by itself is sufficient to explain the larger SSE observed in the joint Go/Nogo task (10ms), compared to that observed in the individual Go/Nogo task (4ms).
Figure 1. The solid arrows (green and red) are the response associated with the color of the stimulus and the dotted arrows (green and red) are the response associated with the position of the stimulus.
Based on the occurrence of the EMG activity of the agonist muscle involved in the task, fractionated-RT showed that coaction shortened both pre-motor time (14ms) and motor time (4ms).
Figure 3. Electromyographical recording of the Flexor Pollicis Brevis muscle
Reaction time was measured from the occurrence of the stimulus to the closure of the switches located under the response keys. Based on the EMG trace, reaction time was fractionated in two RT-components: the premotor time (PMT, from stimulus onset to the onset of the EMG involved in the response) and the motor time (MT, from the EMG onset to the switch closure) (Figure 4).
Figure 6. Motor time (in milliseconds) in joint Go/Nogo and individual Go/Nogo tasks
Results on PMT mimicked the pattern observed on mean RT. Joint-action induced a larger facilitation on IPS trials (joint: 208ms vs. individual: 224ms) than on CNT trials (joint: 219ms vs. individual: 229ms) (F(1,36) = 14.41, p <.001).
Figure 7. Premotor time (in milliseconds) in joint Go/Nogo and individual Go/Nogo tasks, as function of the side location (ipsilateral, IPS vs. contralateral, CNT) of the trial.
Mechanisms underlying the Social Simon Effect?
Social Facilitation
According to social facilitation theory, the larger SSE observed in the joint Go/Nogo task could be explained by a larger benefit observed on simple and automatic response compared to complex and less natural response.
Co-Representation
According to Sebanz and colleagues, the SSE could be attributed to the co-representation of the both co-actor’s actions.
More incorrect activations (Figure 8 and Figure 9) are observed in the joint Go/Nogo compared to the individual Go/Nogo.
Aims
Figure 4. Illustration of the decomposition of RT in premotor time and motor time and incorrect activation trials.
This study aimed to elucidate the mechanisms underlying the social Simon effect (SSE). Electromyographic (EMG) recordings and distributional analyses have been used to assess whether coaction could be attributed to a social facilitation effect or to a co-representation phenomenon.
Incorrect activation trials were separated into two categories: errors and partial errors. As illustrate by the Figure 4, the partial errors correspond to trials in which a correct activation was preceded by an incorrect activation. The force exerted by the non-required effector was not sufficient to elicit an error and were followed by a correct activation reaching response threshold.
Figure 8.
Figure 9.
In the Simon task, the frequency of errors in the initial phase (from D1 to D4) is higher for IPS compared to CNT, illustrating the strength of the automatic response capture. This pattern was not observed in the joint or individual Go/Nogo tasks for which the frequency of errors was equivalent whatever the side location.
Material and Methods
The experiment consisted in two sessions. Participants reported to the laboratory accompanied by a friend for a first session and alone for a second. In the session performed alone, participant completed 960 trials in a standard Simon task (Figure 2B) and 960 trials in an individual Go/Nogo task (Figure 2C). In the session performed with a friend, participants shared a Simon task or in other words completed a joint Go/Nogo task (Figure 2A). The order of the sessions and the order of the cognitive tasks in the individual session were counterbalanced across participants.
Hypothesis
If the SSE is attributed to a social facilitation effect, in the joint Go/Nogo task a larger benefit should be observed on ipsilateral (IPS) trials compared to contralateral (CNT) trials.
Figure 10. Error (in percentage) in the individual Go/Nogo, joint Go/Nogo and Simon tasks as function of the side location of the error
Discussion
- The fact that coaction predominantly affected IPS trials suggests that SSE has more to do with a social facilitation effect than with a co-representation phenomenon.
- Fast impulsive errors pattern observed on conditional accuracy functions (Figure 10) does not argue in favor of the co-representation of the both co-actor’s actions.
- Extra incorrect activations and shortening of the MT suggest an increase in arousal and a lowering of the threshold of the motor response in coaction.
Joint Go/Nogo task
Simon task
Go/Nogo task
References
Sebanz N, Knoblich G, Prinz W. Representing others' actions: just like one's own? Cognition Jul;88(3):B11-21.
Guerin B. Social Facilitation. Cambridge: Cambridge University Press, 2009.
van den Wildenberg WP, Wylie SA, Forstmann BU, Burle B, Hasbroucq T, Ridderinkhof KR. To head or to heed? Beyond the surface of selective action inhibition: a review. Front Hum Neurosci Dec 13;4:222.
If the SSE is attributed to a co-representation of the actions, compared to the Go/Nogo task, we attended in the joint Go/Nogo:
1/ a lengthening of the PMT
2/ extra incorrect activations (error + partial errors)
3/ more frequent fast impulsive errors for IPS than CNT trials
Figure 2. Cognitive tasks completed by a participant