Psychonomic Bulletin & Review

, Volume 21, Issue 5, pp 1165–1173 | Cite as

The resurrection of Tweedledum and Tweedledee: Bimodality cannot distinguish serial and parallel processes

Theoretical Review


Simultaneously presented signals may be processed in serial or in parallel. One potentially valuable indicator of a system’s characteristics may be the appearance of multimodality in the response time (RT) 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 ones, can also make such predictions. We demonstrate via simulations that a multimodal RT 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.


Parallel Serial Response times Bimodality 


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Copyright information

© Psychonomic Society, Inc. 2014

Authors and Affiliations

  • Paul Williams
    • 1
  • Ami Eidels
    • 1
    • 3
  • James T. Townsend
    • 2
  1. 1.University of NewcastleCallaghanAustralia
  2. 2.Indiana UniversityBloomingtonUSA
  3. 3.School of PsychologyUniversity of NewcastleCallaghanAustralia

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