Conflicts During Response Selection Affect Response Programming: Reactions Toward the Source of Stimulation

Simona Buetti, Dirk Kerzel

Research output: Contribution to journalArticlepeer-review


In the Simon effect, participants make a left or right keypress in response to a nonspatial attribute (e.g., color) that is presented on the left or right. Reaction times (RTs) increase when the response activated by the irrelevant stimulus location and the response retrieved by instruction are in conflict. The authors measured RTs and movement parameters (MPs) of pointing responses in a typical Simon task. Their results show that the trajectories veer toward the imperative stimulus. This bias decreased as RTs increased. The authors suggest that the time course of trajectory deviations reflects the resolution of the response conflict over time. Further, time pressure did not affect the size of the Simon effect in MPs or its time course, but strongly reduced the Simon effect in RTs. In contrast, response selection before the onset of a go signal on the left or right did not affect the Simon effect in RTs, but reduced the Simon effect in MPs and reversed the time course. The authors speculate about independent Simon effects associated with response selection and programming.

Original languageEnglish (US)
Pages (from-to)816-834
Number of pages19
JournalJournal of Experimental Psychology: Human Perception and Performance
Issue number3
StatePublished - Jun 2009
Externally publishedYes


  • Simon effect
  • distractor interference
  • pointing movements
  • stimulus-response compatibility
  • stimulus-response congruency

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Arts and Humanities (miscellaneous)
  • Behavioral Neuroscience


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