@article{SellaroDolkColzatoetal.2015,
  author    = {Sellaro, Roberta and Dolk, Thomas and Colzato, Lorenza S. and Liepelt, Roman and Hommel, Bernhard},
  title     = {Referential Coding Does Not Rely on Location Features: Evidence for a Nonspatial Joint Simon Effect},
  series = {Journal of experimental psychology : Human perception and performance},
  volume    = {41},
  journal   = {Journal of experimental psychology : Human perception and performance},
  number    = {1},
  publisher = {American Psychological Association},
  address   = {Washington},
  issn      = {0096-1523},
  doi       = {10.1037/a0038548},
  pages     = {186 -- 195},
  year      = {2015},
  abstract  = {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.},
  language  = {en}
}
@article{StenzelDolkColzatoetal.2014,
  author    = {Stenzel, Anna and Dolk, Thomas and Colzato, Lorenza S. and Sellaro, Roberta and Hommel, Bernhard and Liepelt, Roman},
  title     = {The joint Simon effect depends on perceived agency, but not intentionality, of the alternative action},
  series = {Frontiers in human neuroscienc},
  volume    = {8},
  journal   = {Frontiers in human neuroscienc},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {1662-5161},
  doi       = {10.3389/fnhum.2014.00595},
  pages     = {10},
  year      = {2014},
  abstract  = {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.},
  language  = {en}
}