Poster A112, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
On events and features: An ERP study on sequence effects in a choice/nogo Simon task
Edmund Wascher1, Katharina Hoppe1; 1IfADo - Leibniz Research Centre for Working Environment and Human Factors
Spatial S-R correspondence affects performance even if the location of a stimulus is not task relevant (Simon effect: responses are faster when stimulus location and response location corresponds). The base explanation for this phenomenon is the automatic activation of a spatial code for the irrelevant stimulus location that interferes with the selection of the required response. This activation mechanism may be conditionally modified. In order to control for irrelevant information, after non-corresponding trials automatic response activation may be inhibited. Thus the Simon effect has been found to be eliminated. This finding, however, may be also explained on the level of feature integration. In a Simon task participants had to perform a left/right decision based on letter identity, but only when the letter was surrounded by a particular shape. Letters surrounded by another shape were nogo trials. EEG was recorded from 64 electrodes. Both the repetition of a letter (also after nogo trials) and the repetition of a response led to faster responses. Responses were in particular fast when all features were repeated. The pattern observed is inconsistent with both before mentioned theories. They indicate that priming due to feature repetition may explain most of the effects. This notion can be supported by an increase of N2pc amplitude with location repetition and a decrease of P3 amplitude with response repetitions. Thus, the causes for the adaptation of the Simon effect due to the correspondence in the previous trial may be more trivial than reported so far.
Topic Area: PERCEPTION & ACTION: Vision