Abstract
I attempted to further our understanding of response inhibition by examining three questions concerning how it works. The first question that I examined was what determines the success of response inhibition. This question was examined with the stop-signal paradigm, a prominent experimental setting for the study of response inhibition. I hypothesized that the relative strength of activation and inhibitory processes is a determinant, which led to an examination of graded action of response inhibition. To examine graded response inhibition, several continuous measurements including response force, electromyography (EMG) and the lateralized readiness potential (LRP) derived from electroencephalography (EEG) were employed; and new methods of comparing conditions and of controlling for contributions from response activation were introduced. Results in the present study indicated that response inhibition works in a graded manner. The second question that I examined was how specifically targeted response inhibition is. In line with previous studies, results in the present study indicated that response inhibition works globally to some extent, at least when speeded responses were required. New information about global response inhibition in the present study was that global response inhibition was considered with two distinct lines of research – one line concerns selective response inhibition, where global response inhibition was indicated previously, and the other line concerns the psychological refractory period (PRP) paradigm, which has been a prominent experimental setting for the study of divided attention. The third question that I examined was on what level(s) of processing selective response inhibition and global response inhibition produce their effects. Results in the present study with measurements of response force, EMG and the LRP indicated that global effects of selective response inhibition within the stop-signal paradigm are produced at the motor stage of processing, and that global effects of response inhibition within the PRP paradigm are produced at the response-selection stage of processing.