Perception & Psychophysics

, Volume 58, Issue 6, pp 915–926

Subitizing and counting depend on different attentional mechanisms: Evidence from visual enumeration in afterimages


DOI: 10.3758/BF03205493

Cite this article as:
Simon, T.J. & Vaishnavi, S. Perception & Psychophysics (1996) 58: 915. doi:10.3758/BF03205493


Two experiments showed that, when selective eye movements were disabled by the presentation of stimuli in the form of afterimages, increased inspection time and facilitative stimulus configurations failed to increase the subitizing limit of 4 objects. Afterimages of two to eight dots induced by a photographic flashgun were shown to 3 adult subjects. For more than 4 objects, enumeration errors occurred at a rate of 20%–30%. Enumeration was effectively perfect for 2–4 linearly configured dots, with occasional errors surprisingly occurring in that range when dots appeared in groups of up to 3 items. No errors occurred in nonafterimage control conditions. Enumeration errors were attributed to failures of individuating dots to be counted due to the deactivation of selective eye movements in afterimages. A third experiment supported this interpretation by disabling eye movements with briefly presented stimuli and producing results much like those of the afterimage conditions.

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Copyright information

© Psychonomic Society, Inc. 1996

Authors and Affiliations

  1. 1.School of PsychologyGeorgia Institute of TechnologyAtlanta