There is no central stimulus encoding during saccadic eye shifts: A case against general parallel processing notions

Three experiments are reported about the question whether perceptual processing of a signal viewed during a fixation, can continue during a subsequent saccadic eye shift to another signal. In the first experiment it was found that the size of the effect of degraded signal quality, measured in a traditional choice reaction task, was fully reflected in the duration of the fixation. The results of the second experiment showed that presentation time of the signal had no effect on fixation duration. In a final study the signal was preceded by a tone. Subjects were instructed to start the saccade upon hearing the tone, which had the effect that the signal was only briefly viewed. The results showed, first, that this instruction was hard to obey and, second, that, when obeyed, processing only continued when fixating the next signal and not during the saccade. Together, the results are most consistent with a serial sequence and difficult to reconcile with a parallel notion of perceptual encoding and saccadic shift.