Resurrection of Tweedledum and Tweedledee

Simultaneously presented signals may be processed in serial or in parallel. One potentially valuable indicant of a system’s characteristics may be the appearance of multi-modality in response time distributions. It is known that standard serial models can predict multimodal RT distributions, but it is unknown whether multimodality is diagnostic of serial systems, or whether alternative architectures, such as parallel, can make such predictions. We demonstrate via simulations that a multimodal reaction time distribution is not sufficient by itself to rule out parallel self-terminating processing, even with limited trial numbers. These predictions are discussed within the context of recent data indicating the existence of multimodal distributions in visual search.