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Günther Knoblich studies how people perceive actions and coordinate joint action. His experiments ask how the presence and possible actions of another person change an individual's own performance.^[ref]

In a 2003 experiment with Natalie Sebanz and colleagues, the two responses of a task were distributed between two people. Each participant made only one response. The same task was also performed alone, and compared with a condition where one person made both responses. A spatial stimulus-response compatibility effect appeared when the one-response task was shared with another participant, resembling the effect in the ordinary two-response task.^[ref]

This supplied evidence that another person's available action could enter the organization of one's own response. The comparison was informative because the required individual response could be held constant while the social arrangement changed. A behavioural compatibility effect supports a functional account of action representation; it does not by itself identify a particular neuron type or prove that every possible social context uses one mechanism.

Mouse tracking records a computer pointer's trajectory over time as a behavioral measure. In psycholinguistics, its Cartesian coordinates can reveal differences between trials that end in the same choice. The trajectory complements final accuracy and reaction time by preserving part of the movement toward the response.

Michael Spivey, Marc Grosjean and Günther Knoblich tested 42 participants with two object pictures in opposite upper corners of a screen. Participants started at the bottom center; a prerecorded word named the target 0.5 seconds after the pictures appeared. A candy distractor shared initial sounds with the target candle, while a jacket provided a dissimilar control. Movements showed greater attraction toward the competing object before reaching the correct target.^[ref]

The authors used linear interpolation to compare trajectories at 101 normalized time positions. That procedure preserves relative movement progression while changing its time scale. Display geometry and movement instructions remain part of the measurement; a curve alone is not a uniquely identified mental state.

Natalie Sebanz investigates the cognitive mechanisms that allow people to perform joint action. Her work examines how individuals anticipate a partner's actions and coordinate their own actions with them.^[ref]

In a 2003 experiment with Günther Knoblich and colleagues, two people divided the responses of a spatial stimulus-response compatibility task between them. Each person made one response. A compatibility effect appeared when the task was shared, resembling performance when a single person controlled both responses; it was absent when the one-response task was performed alone.^[ref]

The comparison made another person's role experimentally relevant while retaining the individual's response requirement. It supported the idea that a partner's available action can enter one's own task representation. This is a claim about measured performance under specified conditions; identifying its precise neural implementation requires additional evidence.